History of X-ray astronomy
Encyclopedia
History of X-ray astronomy begins in the 1920's with interest in short wave communications for the U.S. Navy. This led to the study of the ionosphere
. By 1927 interest in going beyond studies with short waves led to developing theories pertaining to putting Goddard's rockets into the upper atmosphere. Theories included detection of ultraviolet
radiation and X-rays at high altitudes. The first successful rocket flight equipped with instrumentation able to detect solar ultraviolet radiation
occurred in 1946. X-ray solar studies began in 1949. By 1973 a solar instrument package orbited on Skylab
providing significant solar data.
In 1965 the Goddard Space Flight Center
program in X-ray astronomy
was initiated with a series of balloon-borne experiments. In the 1970's this was followed by high altitude sounding rocket
experiments, and that was followed by orbiting (satellite) observatories.
The first rocket flight to successfully detect a cosmic source of X-ray emission
was launched in 1962 by a group at American Science and Engineering
(AS&E).
X-ray wavelengths reveal information about the bodies (sources) that emit them.
. The NRL was conducting research on the properties of the ionosphere
(Earth's reflecting layer) because of interest in short wave radio communications. Hubert produced a series of mathematical description
s of the ionosphere during the 1920s and 1930s. In 1927, at the Carnegie Institution of Washington, Hulburt, Gregory Breit
and Merle Tuve
explored the possibility of equipping Robert Goddard's rockets to explore the upper atmosphere. In 1929 Hulburt proposed an experimental program in which a rocket might be instrumented to explore the upper atmosphere. This proposal included detection of ultraviolet
radiation and X rays at high altitudes.
Herbert Friedman
began X-ray solar studies in 1949 and soon reported that the energy of "the solar X-ray spectrum ... is adequate to account for all of E-layer ionization." Thus one of Hulburt's original questions, the source and behavior of the radio-reflecting layer, began to find its answer in space research
.
At the end of the 1930's other studies included the inference of an X-ray corona by optical methods and, in 1949, more direct evidence by detecting X-ray photons.
Because the Earth's atmosphere
blocks X-rays at ground level, Wilhelm Röntgen's discovery had no effect on observational astronomy for the first 50 years. X-ray astronomy
became possible only with the capability to use rockets that far exceeded the altitudes of balloons. In 1948 U.S. researchers used a German-made V-2 rocket to gather the first records of solar x-rays.
The NRL has placed instruments in rockets, satellites, Skylab, and Spacelab 2
Through the 1960s, 70s, 80s, and 90s, the sensitivity of detectors increased greatly during the 60 years of X-ray astronomy. In addition, the ability to focus X-rays has developed enormously—allowing the production of high-quality images.
, Herbert Gursky
, Frank Paolini, and Bruno Rossi
. This rocket flight used a small X-ray detector, which found a very bright source they named Scorpius X-1
, because it was the first X-ray source
found in the constellation Scorpius
.
, such as Uhuru
, Ariel 5, SAS-3, OSO-8 and HEAO-1, developed this field of science at an astounding pace. Scientists hypothesized that X-rays from stellar sources in our galaxy were primarily from a neutron star
in a binary system
with a normal star. In these "X-ray binaries," the X-rays originate from material traveling from the normal star to the neutron star in a process called accretion
. The binary nature of the system allowed astronomers to measure the mass of the neutron star. For other systems, the inferred mass of the X-ray emitting object supported the idea of the existence of black holes, as they were too massive to be neutron stars. Other systems displayed a characteristic X-ray pulse, just as pulsars had been found to do in the radio regime, which allowed a determination of the spin rate of the neutron star
.
Finally, some of these galactic X-ray sources were found to be highly variable. In fact, some sources would appear in the sky, remain bright for a few weeks, and then fade again from view. Such sources are called X-ray transients. The inner regions of some galaxies were also found to emit X-rays. The X-ray emission from these active galactic nuclei is believed to originate from ultra-relativistic gas near a very massive black hole at the galaxy's center. Lastly, a diffuse X-ray emission was found to exist all over the sky.
, EXOSAT
, Ginga, RXTE, ROSAT
, ASCA
, as well as BeppoSAX
, which detected the first afterglow of a gamma-ray burst (GRB). Data from these satellites continues to aid our further understanding of the nature of these sources and the mechanisms by which the X-rays and gamma rays are emitted. Understanding these mechanisms can in turn shed light on the fundamental physics
of our universe. By looking at the sky with X-ray and gamma-ray instruments, we collect important information in our attempt to address questions such as how the universe began and how it evolves, and gain some insight into its eventual fate.
From 1965 to 1972 there were over a dozen balloon-borne experiments (mostly from New Mexico), including the first such to take place from Australia (1966), one in which hard X-ray emission was discovered (albeit with crude angular resolution) from a region towards the galactic center whose centroid is located among subsequently identified sources GX1+4, GX3+1, and GX5-1. A balloon-borne experiment in 1968 was based on the multi-anode multi-layer xenon gas proportional chamber that had recently been developed in our lab and represented the first use of such a high performance instrument for X-ray astronomy.
Due to the attenuation of soft X-rays by the residual atmosphere at balloon altitudes these early experiments were restricted to energies above ~20 keV. Observations down to lower energies were begun with a series of high altitude sounding rocket experiments; by this stage Steve Holt had already joined the program. A 1972 rocket-borne observation of Cas A, the youngest supernova remnant in our galaxy, yielded the first detection of an X-ray spectral line, iron K-line emission at ~7 keV.
An observation of Cyg X-3 a year later with the same instrument yielded an optically thin thermal spectrum for this source and provided the first evidence for strong spectral iron K-line emission from an X-ray binary.
Our large area PCA (Proportional Counter Array) on the current RXTE (Rossi X-ray Timing Explorer
) mission genuinely reflects the heritage of our sounding rocket program. RXTE continues to provide very valuable data as it enters the second decade of successful operation.
Goddard's ASM (All-Sky Monitor) pin-hole X-ray camera on Ariel-5 (1974-1980) was the first X-ray astronomy experiment to use imaging proportional counters (albeit one-dimensional); it provided information on transient sources and the long-term behavior of several bright objects. Jean Swank joined the program in time for the beginning of our OSO-8 experiment (1975-1978), the first broadband (2-40 keV) orbiting observatory based on multi-anode multi-layer proportional chambers, one that showed the power of X-ray spectroscopy; for example, it established that iron K-line emission is a ubiquitous feature of clusters of galaxies..
The HEAO-1 A2 full-sky cosmic X-ray experiment (1977-1979) provided the most comprehensive data (still the most definitive) on the cosmic X-ray background broadband spectrum and large-scale structure, and a much used complete sample of the brightest extragalactic sources; it posed the challenging "spectral paradox" just now being unraveled with new results on evolution (from deep surveys) and on individual source spectra extending into the gamma-ray band. The SSS (Solid State Spectrometer) at the focus of the HEAO-2 Einstein Observatory (1978-1981) grazing incidence telescope was the first high spectral resolution non-dispersive spectrometer to be used for X-ray astronomy, here for energies up to ~3 KeV
, limited by the telescope optics.
By the use of conical foil optics, developed in our lab, the response of a grazing incidence X-ray telescope was extended to 12 keV, amply covering the crucial iron K-band of emission. A cooled Si(Li) solid state detector was used at the focus of such a telescope for the BBXRT (Broad Band X-Ray Telescope) on the Astro-1 shuttle mission (STS-35) on Columbia in December 1990, the first broadband (0.3-12keV) X-ray observatory to use focusing optics.
In collaboration with X-ray astronomers in Japan, Goddard supplied conical foil X-ray optics have been used for the joint Japanese and American ASCA mission (1993-2000). It was the first broadband imaging observatory using CCD non-dispersive spectrometers.
Substantial improvement in the capability of solid-state non-dispersive spectrometers has been achieved in our lab (in collaboration with the University of Wisconsin) by the successful development of quantum calorimeters with resolution better than 10 eV (FWHM). Such spectrometers have been used in a sounding-rocket-borne experiment to study spectral lines from the hot interstellar medium of our galaxy and will soon play a major role in the joint Japanese/American Suzaku orbiting X-ray observatory launched in July 2005.
The critical early stages of this program benefited from highly dedicated technical support by Dale Arbogast, Frank Birsa, Ciro Cancro, Upendra Desai, Henry Doong, Charles Glasser, Sid Jones, and Frank Shaffer. More than 20 graduate students (mostly from the University of Maryland at College Park) have successfully carried out their PhD dissertation research within our X-ray astronomy program. Almost all of these former students have remained actively involved with astrophysics.
was launched from White Sands Proving Grounds Launch Complex (LC) 33. In addition to carrying experiments of the US Naval Research Laboratory for cosmic and solar radiation, temperature, pressure, ionosphere, and photography, there was on board a solar X-ray test detector, which functioned properly. The missile reached an apogee of 166 km.
As part of a collaboration between the US Naval Research Laboratory (NRL) and the Signal Corps Engineering Laboratory (SCEL) of the University of Michigan, another V-2 (V-2 42 configuration) was launched from White Sands LC33 on December 9, 1948 at 16:08 GMT (09:08 local time). The missile reached an apogee of 108.7 km and carried aeronomy (winds, pressure, temperature), solar X-ray and radiation, and biology experiments.
On January 28, 1949, an NRL X-ray detector (Blossom) was placed in the nose cone of a V-2 rocket and launched at White Sands Missile Range
in New Mexico. X-rays from the Sun were detected. Apogee: 60 km.
A second collaborative effort (NRL/SCEL) using a V-2 UM-3 configuration launched on April 11, 1949 at 22:05 GMT. Experiments included solar X-ray detection, apogee: 87.4 km.
NRL Ionosphere 1 solar X-ray, ionosphere, meteorite mission launched a V-2 on September 29, 1949 from White Sands at 16:58 GMT and reached 151.1 km.
Using V-2 53 configuration a solar X-ray experiment was launched on February 17, 1950 from White Sands LC 33 at 18:01 GMT reaching an apogee of 148 km.
The last V-2 launch number TF2/TF3 came on August 22, 1952 07:33 GMT from White Sands reaching an apogee of 78.2 km and carried experiments
On April 19, 1960, an Office of Naval Research
Aerobee Hi made a series of X-ray photographs of the Sun from an altitude of 208 km. The mainstay of the US IGY rocket stable was the Aerobee Hi, which was modified and improved to create the Aerobee 150.
An Aerobee 150 rocket launched on June 12, 1962 detected the first X-rays from other celestial sources (Scorpius X-1).
was probably the most successful of the many sounding rocket programs. The first launched in 1957 from Woomera
, Australia and its 441st and final launch took place from Esrange
, Sweden on 2 May 2005. Launches were carried out from sites in Australia, Europe, and South America, with use by NASA
, the European Space Research Organisation (ESRO
), and German
and Swedish
space organizations. Skylark was used to obtain the first good-quality X-ray images of the solar corona.
The first X-ray surveys of the sky in the Southern Hemisphere were provided by Skylark launches. It was also used with high precision in September and October 1972 in an effort to locate the optical counterpart of X-ray source GX3+1 by lunar occultation.
was successfully launched on April 14, 1964 from Hammaguir
a, LC Blandine carrying experiments to measure UV and X-ray intensities and the FU110 to measure UV intensity from the atomic H
(Lyman-α) line, and again on November 4, 1964.
at 1:54 a.m. EDT. As the world's first orbiting astronomical observatory, SOLRAD I determined that radio fade-outs were caused by solar X-ray emissions.
The first in a series of 8 successfully launched Orbiting Solar Observatories
(OSO 1, launched on March 7, 1963) had as its primary mission to measure solar electromagnetic radiation in the UV, X-ray, and gamma-ray regions.
The first USA satellite which detected cosmic X-rays was the Third Orbiting Solar Observatory, or OSO-3, launched on March 8, 1967. It was intended primarily to observe the Sun, which it did very well during its 2 year lifetime, but it also detected a flaring episode from the source Sco X-1 and measured the diffuse cosmic X-ray background.
OSO 5 was launched on January 22, 1969, and lasted until July 1975. It was the 5th satellite put into orbit as part of the Orbiting Solar Observatory
program. This program was intended to launch a series of nearly identical satellites to cover an entire 11-year solar cycle. The circular orbit had an altitude of 555 km and an inclination of 33°. The spin rate of the satellite was 1.8 s. The data produced a spectrum of the diffuse background over the energy range 14-200 keV.
OSO 6 was launched on August 9, 1969. Its orbital period was ~95 min. The spacecraft had a spin rate of 0.5 rps. On board was a hard X-ray detector (27-189 keV) with a 5.1 cm2 NaI(Tl) scintillator, collimated to 17° × 23° FWHM. The system had 4 energy channels (separated 27-49-75-118-189 keV). The detector spun with the spacecraft on a plane containing the Sun direction within ± 3.5°. Data were read with alternate 70 ms and 30 ms integrations for 5 intervals every 320 ms.
TD-1A
was put in a nearly circular polar sun-synchronous orbit, with apogee 545 km, perigee 533 km, and inclination 97.6°. It was ESRO's first 3-axis stabilized satellite, with one axis pointing to the Sun to within ±5°. The optical axis was maintained perpendicular to the solar pointing axis and to the orbital plane. It scanned the entire celestial sphere every 6 months, with a great circle being scanned every satellite revolution. After about 2 months of operation, both of the satellite's tape recorders failed. A network of ground stations was put together so that real-time telemetry from the satellite was recorded for about 60% of the time. After 6 months in orbit, the satellite entered a period of regular eclipses as the satellite passed behind the Earth—cutting off sunlight to the solar panels. The satellite was put into hibernation for 4 months, until the eclipse period passed, after which systems were turned back on and another 6 months of observations were made. TD-1A
was primarily a UV mission however it carried both a cosmic X-ray and a gamma-ray detector. TD-1A reentered on January 9, 1980.
was primarily a solar observatory designed to point a battery of UV and X-ray telescopes at the Sun from a platform mounted on a cylindrical wheel. The detectors for observing cosmic X-ray sources were X-ray proportional counters. The hard X-ray telescope operated over the energy range 7 - 550 keV. OSO 7 performed an X-ray All-sky survey and discovered the 9-day periodicity in Vela X-1
which led to its optical identification as a HMXRB. OSO 7 was launched on September 29, 1971 and operated until May 18, 1973.
Skylab
, a science and engineering laboratory, was launched into Earth orbit by a Saturn V rocket on May 14, 1973. Detailed X-ray studies of the Sun were performed. The S150 experiment performed a faint X-ray source survey. The S150 was mounted atop the SIV-B upper stage of the Saturn 1B rocket which orbited briefly behind and below Skylab on July 28, 1973. The entire SIV-B stage underwent a series of preprogrammed maneuvers, scanning about 1° every 15 seconds, to allow the instrument to sweep across selected regions of the sky. The pointing direction was determined during data processing, using the inertial guidance system of the SIV-B stage combined with information from two visible star sensors which formed part of the experiment. Galactic X-ray sources were observed with the S150 experiment. The experiment was designed to detect 4.0-10.0 nm photons. It consisted of a single large (~1500 cm2) proportional counter, electrically divided by fine wire ground planes into separate signal-collecting areas and looking through collimator vanes. The collimators defined 3 intersecting fields of view (~2 × 20°) on the sky, which allowed source positions to be determined to ~ 30'. The front window of the instrument consisted of a 2 µm thick plastic sheet. The counter gas was a mixture of argon and methane. Analysis of the data from the S150 experiment provided strong evidence that the soft X-ray background cannot be explained as the cumulative effect of many unresolved point sources.
Skylab's solar studies: UV and X-ray solar photography for highly ionized atoms, X-ray spectrography of solar flares and active regions, and X-ray emissions of lower solar corona.
Salyut 4
space station was launched on December 26, 1974. It was in an orbit of 355 × 343 km, with an orbital period of 91.3 minutes, inclined at 51.6°. The X-ray telescope began observations on January 15, 1975.
Orbiting Solar Observatory (OSO 8) was launched on June 21, 1975. While OSO 8's primary objective was to observe the Sun, four instruments were dedicated to observations of other celestial X-ray sources brighter than a few milliCrab. A sensitivity of 0.001 of the Crab nebula source (= 1 "mCrab"). OSO 8 ceased operations on October 1, 1978.
Prognoz 6 carried two NaI(Tl) scintillators (2-511 keV, 2.2-98 keV), and a proportional counter
(2.2-7 keV) to study solar X-rays.
The Space Test Program spacecraft P78-1
or Solwind was launched on February 24, 1979 and continued operating until September 13, 1985, when it was shot down in orbit during an Air Force ASM-135 ASAT
test. The platform was of the Orbiting Solar Observatory (OSO) type, with a solar-oriented sail and a rotating wheel section. P78-1 was in a noon-midnight, Sun-synchronous orbit at 600 km altitude. The orbital inclination of 96° implied that a substantial fraction of the orbit was spent at high latitude, where the particle background prevented detector operation. In-flight experience showed that good data were obtained between 35° N and 35° S geomagnetic latitude outside the South Atlantic Anomaly. This yields an instrument duty cycle of 25-30%. Telemetry data were obtained for about 40-50% of the orbits, yielding a net data return of 10-15%. Though this data rate appears low, it means that about 108 seconds of good data reside in the XMON data base.
Data from the P78-1 X-Ray Monitor experiment offered source monitoring with a sensitivity comparable to that of instruments flown on SAS-3, OSO-8
, or Hakucho
, and the advantages of longer observing times and unique temporal coverage. Five fields of inquiry were particularly well suited for investigation with P78-1 data:
Launched on February 21, 1981, the Hinotori satellite observations of the 1980s pioneered hard X-ray imaging of solar flares.
Tenma
was the second Japanese X-ray astronomy satellite launched on February 20, 1983. Tenma carried GSFC
detectors which had an improved energy resolution (by a factor of 2) compared to proportional counters and performed the first sensitive measurements of the iron spectral region for many astronomical objects. Energy range: 0.1-60 keV; gas scintillator proportional counter: 10 units of 80 cm2 each, FOV ~ 3° (FWHM), 2-60 keV; transient source monitor: 2-10 keV.
The Soviet Astron orbital station
was designed primarily for UV and X-ray astrophysical observations. It was injected into orbit on March 23, 1983. The satellite was put into a highly elliptical orbit, ~200,000 × 2,000 km. The orbit kept the craft far away from the Earth for 3.5 out of every 4 days. It was outside of the Earth's shadow and radiation belts for 90% of the time. The second major experiment, SKR-02M, aboard Astron was an X-ray spectrometer, which consisted of a proportional counter sensitive to 2-25 keV X-rays, with an effective area of 0.17 m2. The FOV was 3° × 3° (FWHM). Data could be telemetered in 10 energy channels. The instrument began taking data on April 3, 1983.
Spacelab
1 was the first Spacelab mission in orbit in the payload bay of the Space Shuttle (STS-9) between November 28 and December 8, 1983. An X-ray spectrometer, measuring 2-30 keV photons (although 2-80 keV was possible), was on the pallet. The primary science objective was to study detailed spectral features in cosmic sources and their temporal changes. The instrument was a gas scintillation proportional counter (GSPC) with ~ 180 cm2 area and energy resolution of 9% at 7 keV. The detector was collimated to a 4.5° (FWHM) FOV. There were 512 energy channels.
Spartan 1 was deployed from the Space Shuttle Discovery (STS-51G) on June 20, 1985 and retrieved 45.5 hours later. The X-ray detectors aboard the Spartan platform were sensitive to the energy range 1-12 keV. The instrument scanned its target with narrowly collimated (5' × 3°) GSPCs. There were 2 identical sets of counters, each having ~ 660 cm2 effective area. Counts were accumulated for 0.812 s into 128 energy channels. The energy resolution was 16% at 6 keV. During its 2 days of flight, Spartan-1 observed the Perseus cluster of galaxies and our galactic center region.
Ginga was launched on February 5, 1987. The primary instrument for observations was the Large Area Proportional Counter (LAC).
The European Retrievable Carrier (EURECA) was launched July 31, 1992 by the Space Shuttle Atlantis, and put into an orbit at an altitude of 508 km. It began its scientific mission on August 7, 1992. EURECA was retrieved on July 1, 1993 by the Space Shuttle Endeavor and returned to Earth. On board was the WATCH or Wide Angle Telescope for Cosmic Hard X-rays instrument. The WATCH instrument was sensitive to 6-150 keV photons. The total field of view covered 1/4 of the celestial sphere. During its 11 month lifetime, EURECA tracked the Sun and WATCH gradually scanned across the entire sky. Some 2 dozen known X-ray sources were monitored—some for more than 100 days—and a number of new X-ray transient
s were discovered.
The Diffuse X-ray Spectrometer (DXS) STS-54
package was flown as an attached payload in January, 1993 to obtain spectra of the diffuse soft X-ray background. DXS obtained the first-ever high resolution spectra of the diffuse soft X-ray background in the energy band from 0.15 to 0.28 keV (4.3-8.4 nm).
or Sco X-1. There are 88 official constellations. Often the first X-ray source is a transient.
As X-ray sources have been better located, many of them have been isolated to extragalactic regions such as the Large Magellanic Cloud (LMC). When there are often many individually discernible sources, the first one identified is usually designated as the extragalactic source X-1, e.g., Small Magellanic Cloud (SMC) X-1, a HMXRB, at 01h15m14s -73h42m22s.
These early X-ray sources still are studied and often produce significant results. For example, Serpens X-1.
As of August 27, 2007 discoveries concerning asymmetric iron line broadening and their implications for relativity have been a topic of much excitement. With respect to the asymmetric iron line broadening, Edward Cackett of the University of Michigan
commented, "We're seeing the gas whipping around just outside the neutron star's surface,". "And since the inner part of the disk obviously can't orbit any closer than the neutron star's surface, these measurements give us a maximum size of the neutron star's diameter. The neutron stars can be no larger than 18 to 20.5 miles across, results that agree with other types of measurements."
"We've seen these asymmetric lines from many black holes, but this is the first confirmation that neutron stars can produce them as well. It shows that the way neutron stars accrete matter is not very different from that of black holes, and it gives us a new tool to probe Einstein's theory", says Tod Strohmayer of NASA
's Goddard Space Flight Center
.
"This is fundamental physics", says Sudip Bhattacharyya also of NASA's in Greenbelt, Maryland
and the University of Maryland
. "There could be exotic kinds of particles or states of matter, such as quark matter, in the centers of neutron stars, but it's impossible to create them in the lab. The only way to find out is to understand neutron stars."
Using XMM-Newton
, Bhattacharyya and Strohmayer observed Serpens X-1, which contains a neutron star and a stellar companion. Cackett and Jon Miller of the University of Michigan
, along with Bhattacharyya and Strohmayer, used Suzaku
's superb spectral capabilities to survey Serpens X-1. The Suzaku data confirmed the XMM-Newton result regarding the iron line in Serpens X-1.
by constellation
contains 59 sources as of December 1, 1969, that at the least had an X-ray flux published in the literature.
(RA) and Declination
(Dec) of the object. For example, 4U 0115+63, 4th Uhuru
catalog, RA=01 hr 15 min, Dec=+63°; 3S 1820-30 is the SAS-3 catalog; EXO 0748-676 is an Exosat
catalog entry; HEAO 1 uses H; Ariel 5 is 3A; Ginga sources are in GS; general X-ray sources are in the X catalog. Of the early satellites, the Vela
series X-ray sources have been cataloged.
The Uhuru
X-ray satellite made extensive observations and produced at least 4 catalogs wherein previous catalog designations were improved and relisted: 1ASE or 2ASE 1615+38 would appear successively as 2U 1615+38, 3U 1615+38, and 4U 1615+3802, for example. After over a year of initial operation the first catalog (2U) was produced. The third Uhuru
catalog was published in 1974. The fourth and final Uhuru catalog included 339 sources.
Although apparently not containing extrasolar sources from the earlier OSO satellites, the MIT/OSO 7 catalog contains 185 sources from the OSO 7
detectors and sources from the 3U catalog.
The 3rd Ariel 5 SSI Catalog (designated 3A) contains a list of X-ray sources detected by the University of Leicester's Sky Survey Instrument (SSI) on the Ariel 5 satellite. This catalog contains both low and high galactic latitude sources and includes some sources observed by HEAO 1, Einstein
, OSO 7
, SAS 3, Uhuru
, and earlier, mainly rocket, observations. The second Ariel catalog (designated 2A) contains 105 X-ray sources observed before April 1, 1977. Prior to 2A some sources were observed that may not have been included.
The 842 sources in the HEAO A-1 X-ray source catalog were detected with the NRL Large Area Sky Survey Experiment on the HEAO 1 satellite.
When EXOSAT
was slewing between different pointed observations from 1983 to 1986, it scanned a number of X-ray sources (1210). From this the EXOSAT Medium Energy Slew Survey catalog was created. From the use of the Gas Scintillation Proportional Counter (GSPC) on board EXOSAT, a catalog of iron lines from some 431 sources was made available.
, while 32% are supergiant/X-ray binaries (SGXB).
For all the main-sequence and subgiant stars of spectral types A, F, G, and K and luminosity classes IV and V listed in the Bright Star Catalogue (BSC, also known as the HR Catalogue) that have been detected as X-ray sources in the ROSAT All-Sky Survey (RASS), there is the RASSDWARF - RASS A-K Dwarfs/Subgiants Catalog. The total number of RASS sources amounts to ~150,000 and in the BSC 3054 late-type main-sequence and subgiant stars of which 980 are in the catalog, with a chance coincidence of 2.2% (21.8 of 980).
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
. By 1927 interest in going beyond studies with short waves led to developing theories pertaining to putting Goddard's rockets into the upper atmosphere. Theories included detection of ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation and X-rays at high altitudes. The first successful rocket flight equipped with instrumentation able to detect solar ultraviolet radiation
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
occurred in 1946. X-ray solar studies began in 1949. By 1973 a solar instrument package orbited on Skylab
Skylab
Skylab was a space station launched and operated by NASA, the space agency of the United States. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V rocket, with a mass of...
providing significant solar data.
In 1965 the Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...
program in X-ray astronomy
X-ray astronomy
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and...
was initiated with a series of balloon-borne experiments. In the 1970's this was followed by high altitude sounding rocket
Sounding rocket
A sounding rocket, sometimes called a research rocket, is an instrument-carrying rocket designed to take measurements and perform scientific experiments during its sub-orbital flight. The origin of the term comes from nautical vocabulary, where to sound is to throw a weighted line from a ship into...
experiments, and that was followed by orbiting (satellite) observatories.
The first rocket flight to successfully detect a cosmic source of X-ray emission
Astronomical object
Astronomical objects or celestial objects are naturally occurring physical entities, associations or structures that current science has demonstrated to exist in the observable universe. The term astronomical object is sometimes used interchangeably with astronomical body...
was launched in 1962 by a group at American Science and Engineering
American Science and Engineering
American Science and Engineering Inc, is a US manufacturer of X-ray equipment and related technologies, originating in 1958 as a developer for NASA, with an early focus on X-ray astronomy led by Riccardo Giacconi...
(AS&E).
X-ray wavelengths reveal information about the bodies (sources) that emit them.
1920's to the 1940's
The Naval Research Laboratory (NRL) opened in 1923. After E.O. Hulburt arrived there in 1924 he studied physical opticsPhysical optics
In physics, physical optics, or wave optics, is the branch of optics which studies interference, diffraction, polarization, and other phenomena for which the ray approximation of geometric optics is not valid...
. The NRL was conducting research on the properties of the ionosphere
Ionosphere
The ionosphere is a part of the upper atmosphere, comprising portions of the mesosphere, thermosphere and exosphere, distinguished because it is ionized by solar radiation. It plays an important part in atmospheric electricity and forms the inner edge of the magnetosphere...
(Earth's reflecting layer) because of interest in short wave radio communications. Hubert produced a series of mathematical description
Mathematical physics
Mathematical physics refers to development of mathematical methods for application to problems in physics. The Journal of Mathematical Physics defines this area as: "the application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and...
s of the ionosphere during the 1920s and 1930s. In 1927, at the Carnegie Institution of Washington, Hulburt, Gregory Breit
Gregory Breit
Gregory Breit was a Russian-born American physicist and professor at universities in New York, Wisconsin, Yale, and Buffalo...
and Merle Tuve
Merle Tuve
Merle Anthony Tuve, PhD was an American scientist and geophysicist who was the founding director of the Johns Hopkins University Applied Physics Laboratory. He was a pioneer in the use of pulsed radio waves whose discoveries opened the way to the development of radar and nuclear...
explored the possibility of equipping Robert Goddard's rockets to explore the upper atmosphere. In 1929 Hulburt proposed an experimental program in which a rocket might be instrumented to explore the upper atmosphere. This proposal included detection of ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation and X rays at high altitudes.
Herbert Friedman
Herbert Friedman
Herbert Friedman was an American pioneer in the application of sounding rockets to solar physics, aeronomy, and astronomy. He was also a statesman and public advocate for science...
began X-ray solar studies in 1949 and soon reported that the energy of "the solar X-ray spectrum ... is adequate to account for all of E-layer ionization." Thus one of Hulburt's original questions, the source and behavior of the radio-reflecting layer, began to find its answer in space research
Space science
The term space science may mean:* The study of issues specifically related to space travel and space exploration, including space medicine.* Science performed in outer space ....
.
At the end of the 1930's other studies included the inference of an X-ray corona by optical methods and, in 1949, more direct evidence by detecting X-ray photons.
Because the Earth's atmosphere
Earth's atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention , and reducing temperature extremes between day and night...
blocks X-rays at ground level, Wilhelm Röntgen's discovery had no effect on observational astronomy for the first 50 years. X-ray astronomy
X-ray astronomy
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and...
became possible only with the capability to use rockets that far exceeded the altitudes of balloons. In 1948 U.S. researchers used a German-made V-2 rocket to gather the first records of solar x-rays.
The NRL has placed instruments in rockets, satellites, Skylab, and Spacelab 2
Through the 1960s, 70s, 80s, and 90s, the sensitivity of detectors increased greatly during the 60 years of X-ray astronomy. In addition, the ability to focus X-rays has developed enormously—allowing the production of high-quality images.
1960's
The study of astronomical objects at the highest energies of X-rays and gamma rays began in the early 1960s. Before then, scientists knew only that the Sun was an intense source in these wavebands. Earth's atmosphere absorbs most X-rays and gamma rays, so rocket flights that could lift scientific payloads above Earth's atmosphere were needed. The first rocket flight to successfully detect a cosmic source of X-ray emission was launched in 1962 by a group at American Science and Engineering (AS&E). The team of scientists on this project included Riccardo GiacconiRiccardo Giacconi
Riccardo Giacconi is an Italian/American Nobel Prize-winning astrophysicist who laid the foundations of X-ray astronomy. He is currently a professor at the Johns Hopkins University.- Biography :...
, Herbert Gursky
Herbert Gursky
Herbert Gursky was the Superintendent of the Naval Research Laboratory's Space Science Division and Chief Scientist of the E.O. Hulburt Center for Space Research.-Biography:...
, Frank Paolini, and Bruno Rossi
Bruno Rossi
Bruno Benedetto Rossi was a leading Italian-American experimental physicist. He made major contributions to cosmic ray and particle physics from 1930 through the 1950s, and pioneered X-ray astronomy and space plasma physics in the 1960s.-Biography:Rossi was born in Venice, Italy...
. This rocket flight used a small X-ray detector, which found a very bright source they named Scorpius X-1
Scorpius X-1
Scorpius X-1 is an X-ray source located roughly 9000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest source of X-rays in the sky...
, because it was the first X-ray source
X-ray astronomy
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and...
found in the constellation Scorpius
Scorpius
Scorpius, sometimes known as Scorpio, is one of the constellations of the zodiac. Its name is Latin for scorpion, and its symbol is . It lies between Libra to the west and Sagittarius to the east...
.
1970's
In the 1970s, dedicated X-ray astronomy satellitesX-ray astronomy satellites
X-ray astronomy satellites study X-ray emissions from celestial objects. Satellites, which can detect and transmit data about the X-ray emissions are deployed as part of branch of space science known as X-ray astronomy...
, such as Uhuru
Uhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
, Ariel 5, SAS-3, OSO-8 and HEAO-1, developed this field of science at an astounding pace. Scientists hypothesized that X-rays from stellar sources in our galaxy were primarily from a neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
in a binary system
Binary system (astronomy)
A binary system is an astronomical term referring to two objects in space which are so close that their gravitational interaction causes them to orbit about a common center of mass. Some definitions A binary system is an astronomical term referring to two objects in space (usually stars, but also...
with a normal star. In these "X-ray binaries," the X-rays originate from material traveling from the normal star to the neutron star in a process called accretion
Accretion (astrophysics)
In astrophysics, the term accretion is used for at least two distinct processes.The first and most common is the growth of a massive object by gravitationally attracting more matter, typically gaseous matter in an accretion disc. Accretion discs are common around smaller stars or stellar remnants...
. The binary nature of the system allowed astronomers to measure the mass of the neutron star. For other systems, the inferred mass of the X-ray emitting object supported the idea of the existence of black holes, as they were too massive to be neutron stars. Other systems displayed a characteristic X-ray pulse, just as pulsars had been found to do in the radio regime, which allowed a determination of the spin rate of the neutron star
Neutron star
A neutron star is a type of stellar remnant that can result from the gravitational collapse of a massive star during a Type II, Type Ib or Type Ic supernova event. Such stars are composed almost entirely of neutrons, which are subatomic particles without electrical charge and with a slightly larger...
.
Finally, some of these galactic X-ray sources were found to be highly variable. In fact, some sources would appear in the sky, remain bright for a few weeks, and then fade again from view. Such sources are called X-ray transients. The inner regions of some galaxies were also found to emit X-rays. The X-ray emission from these active galactic nuclei is believed to originate from ultra-relativistic gas near a very massive black hole at the galaxy's center. Lastly, a diffuse X-ray emission was found to exist all over the sky.
1980's to the present
The study of X-ray astronomy continued to be carried out using data from a host of satellites that were active from the 1980s to the early 2000s: the HEAO ProgramHEAO Program
The High Energy Astronomy Observatory Program was a NASA program of the late 1970s and early 1980s that included a series of three large low-Earth-orbiting spacecraft for X-ray and Gamma-Ray astronomy and Cosmic-Ray investigations. After launch, they were denoted HEAO 1, HEAO 2 , and HEAO 3,...
, EXOSAT
EXOSAT
The European X-ray Observatory Satellite , originally named HELOS, was operational from May 1983 until April 1986 and in that time made 1780 observations in the X-ray band of most classes of astronomical object including active galactic nuclei, stellar coronae, cataclysmic variables, white dwarfs,...
, Ginga, RXTE, ROSAT
ROSAT
ROSAT was a German Aerospace Center-led satellite X-ray telescope, with instruments built by Germany, the UK and the US...
, ASCA
Advanced Satellite for Cosmology and Astrophysics
ASCA is the fourth cosmic X-ray astronomy mission by Japan's , and the second for which the United States is providing part of the scientific payload. The satellite was successfully launched on February 20, 1993. The first eight months of the ASCA mission were devoted to performance verification...
, as well as BeppoSAX
BeppoSAX
BeppoSAX was an Italian–Dutch satellite for X-ray astronomy which played a crucial role in resolving the origin of gamma-ray bursts , the most energetic events known in the universe...
, which detected the first afterglow of a gamma-ray burst (GRB). Data from these satellites continues to aid our further understanding of the nature of these sources and the mechanisms by which the X-rays and gamma rays are emitted. Understanding these mechanisms can in turn shed light on the fundamental physics
Physics
Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...
of our universe. By looking at the sky with X-ray and gamma-ray instruments, we collect important information in our attempt to address questions such as how the universe began and how it evolves, and gain some insight into its eventual fate.
Balloons
In 1965, at the suggestion of Frank McDonald, Elihu Boldt initiated Goddard's program in X-ray astronomy with a series of balloon-borne experiments. At an early stage he was joined by Peter Serlemitsos, who had just completed his PhD space physics thesis on magnetospheric electrons, and by Guenter Riegler, a University of Maryland physics graduate student interested in doing his dissertation research in astrophysics.From 1965 to 1972 there were over a dozen balloon-borne experiments (mostly from New Mexico), including the first such to take place from Australia (1966), one in which hard X-ray emission was discovered (albeit with crude angular resolution) from a region towards the galactic center whose centroid is located among subsequently identified sources GX1+4, GX3+1, and GX5-1. A balloon-borne experiment in 1968 was based on the multi-anode multi-layer xenon gas proportional chamber that had recently been developed in our lab and represented the first use of such a high performance instrument for X-ray astronomy.
Due to the attenuation of soft X-rays by the residual atmosphere at balloon altitudes these early experiments were restricted to energies above ~20 keV. Observations down to lower energies were begun with a series of high altitude sounding rocket experiments; by this stage Steve Holt had already joined the program. A 1972 rocket-borne observation of Cas A, the youngest supernova remnant in our galaxy, yielded the first detection of an X-ray spectral line, iron K-line emission at ~7 keV.
Rockets
The figure to the right shows 15-second samples of the raw counts (per 20.48ms) observed in a 1973 sounding-rocket-borne exposure to three of the X-ray brightest binary sources in our galaxy: Her X-1 (1.7 days), Cyg X-3 (0.2 day), and Cyg X-1 (5.6 days). The 1.24 second pulsar period associated with Her X-1 is immediately evident from the data, while the rate profile for Cyg X-3 is completely consistent with the statistical fluctuations in counts expected for a source that is constant, at least for the 15s duration of the exposure shown; the Cyg X-1 data, on the other hand, clearly exhibit the chaotic "shot noise" behavior characteristic of this black-hole candidate and also provided preliminary evidence for the additional feature of millisecond "burst" sub-structure, noted for the first time in this observation. The sharp cut-off at ~24 keV in the flat spectrum observed for Her X-1 in this exposure provided the first reported evidence for radiative transfer effects to be associated with a highly magnetized plasma near the surface of a neutron star. The black-body spectral component observed for Cyg X-3 during this experiment gave strong evidence that this emission is from the immediate vicinity of a compact object the size of a neutron star.An observation of Cyg X-3 a year later with the same instrument yielded an optically thin thermal spectrum for this source and provided the first evidence for strong spectral iron K-line emission from an X-ray binary.
Orbiting observatories
Rossi X-ray Timing Explorer
The Rossi X-ray Timing Explorer is a satellite that observes the time structure of astronomical X-ray sources. The RXTE has three instruments—the Proportional Counter Array, the High-Energy X-ray Timing Experiment , and one instrument called the All Sky Monitor...
) mission genuinely reflects the heritage of our sounding rocket program. RXTE continues to provide very valuable data as it enters the second decade of successful operation.
Goddard's ASM (All-Sky Monitor) pin-hole X-ray camera on Ariel-5 (1974-1980) was the first X-ray astronomy experiment to use imaging proportional counters (albeit one-dimensional); it provided information on transient sources and the long-term behavior of several bright objects. Jean Swank joined the program in time for the beginning of our OSO-8 experiment (1975-1978), the first broadband (2-40 keV) orbiting observatory based on multi-anode multi-layer proportional chambers, one that showed the power of X-ray spectroscopy; for example, it established that iron K-line emission is a ubiquitous feature of clusters of galaxies..
The HEAO-1 A2 full-sky cosmic X-ray experiment (1977-1979) provided the most comprehensive data (still the most definitive) on the cosmic X-ray background broadband spectrum and large-scale structure, and a much used complete sample of the brightest extragalactic sources; it posed the challenging "spectral paradox" just now being unraveled with new results on evolution (from deep surveys) and on individual source spectra extending into the gamma-ray band. The SSS (Solid State Spectrometer) at the focus of the HEAO-2 Einstein Observatory (1978-1981) grazing incidence telescope was the first high spectral resolution non-dispersive spectrometer to be used for X-ray astronomy, here for energies up to ~3 KeV
Electronvolt
In physics, the electron volt is a unit of energy equal to approximately joule . By definition, it is equal to the amount of kinetic energy gained by a single unbound electron when it accelerates through an electric potential difference of one volt...
, limited by the telescope optics.
By the use of conical foil optics, developed in our lab, the response of a grazing incidence X-ray telescope was extended to 12 keV, amply covering the crucial iron K-band of emission. A cooled Si(Li) solid state detector was used at the focus of such a telescope for the BBXRT (Broad Band X-Ray Telescope) on the Astro-1 shuttle mission (STS-35) on Columbia in December 1990, the first broadband (0.3-12keV) X-ray observatory to use focusing optics.
In collaboration with X-ray astronomers in Japan, Goddard supplied conical foil X-ray optics have been used for the joint Japanese and American ASCA mission (1993-2000). It was the first broadband imaging observatory using CCD non-dispersive spectrometers.
Substantial improvement in the capability of solid-state non-dispersive spectrometers has been achieved in our lab (in collaboration with the University of Wisconsin) by the successful development of quantum calorimeters with resolution better than 10 eV (FWHM). Such spectrometers have been used in a sounding-rocket-borne experiment to study spectral lines from the hot interstellar medium of our galaxy and will soon play a major role in the joint Japanese/American Suzaku orbiting X-ray observatory launched in July 2005.
The critical early stages of this program benefited from highly dedicated technical support by Dale Arbogast, Frank Birsa, Ciro Cancro, Upendra Desai, Henry Doong, Charles Glasser, Sid Jones, and Frank Shaffer. More than 20 graduate students (mostly from the University of Maryland at College Park) have successfully carried out their PhD dissertation research within our X-ray astronomy program. Almost all of these former students have remained actively involved with astrophysics.
The USA V-2 period
The beginning of the search for X-ray sources from above the Earth's atmosphere was on August 5, 1948 12:07 GMT. A US Army V-2 as part of Project HermesHermes project
The Hermes project was an United States Army Ordnance Corps rocket program ....
was launched from White Sands Proving Grounds Launch Complex (LC) 33. In addition to carrying experiments of the US Naval Research Laboratory for cosmic and solar radiation, temperature, pressure, ionosphere, and photography, there was on board a solar X-ray test detector, which functioned properly. The missile reached an apogee of 166 km.
As part of a collaboration between the US Naval Research Laboratory (NRL) and the Signal Corps Engineering Laboratory (SCEL) of the University of Michigan, another V-2 (V-2 42 configuration) was launched from White Sands LC33 on December 9, 1948 at 16:08 GMT (09:08 local time). The missile reached an apogee of 108.7 km and carried aeronomy (winds, pressure, temperature), solar X-ray and radiation, and biology experiments.
On January 28, 1949, an NRL X-ray detector (Blossom) was placed in the nose cone of a V-2 rocket and launched at White Sands Missile Range
White Sands Missile Range
White Sands Missile Range is a rocket range of almost in parts of five counties in southern New Mexico. The largest military installation in the United States, WSMR includes the and the WSMR Otera Mesa bombing range...
in New Mexico. X-rays from the Sun were detected. Apogee: 60 km.
A second collaborative effort (NRL/SCEL) using a V-2 UM-3 configuration launched on April 11, 1949 at 22:05 GMT. Experiments included solar X-ray detection, apogee: 87.4 km.
NRL Ionosphere 1 solar X-ray, ionosphere, meteorite mission launched a V-2 on September 29, 1949 from White Sands at 16:58 GMT and reached 151.1 km.
Using V-2 53 configuration a solar X-ray experiment was launched on February 17, 1950 from White Sands LC 33 at 18:01 GMT reaching an apogee of 148 km.
The last V-2 launch number TF2/TF3 came on August 22, 1952 07:33 GMT from White Sands reaching an apogee of 78.2 km and carried experiments
- solar X-ray for NRL,
- cosmic radiation for the National Institute of Health (NIH), and
- sky brightness for the Air Research and Development Command.
Aerobee period
The first successful launch of an Aerobee occurred on May 5, 1952 13:44 GMT from White Sands Proving Grounds launch complex LC35. It was an Aerobee RTV-N-10 configuration reaching an apogee of 127 km with NRL experiments for solar X-ray and ultraviolet detection.Office of Naval Research
The Office of Naval Research , headquartered in Arlington, Virginia , is the office within the United States Department of the Navy that coordinates, executes, and promotes the science and technology programs of the U.S...
Aerobee Hi made a series of X-ray photographs of the Sun from an altitude of 208 km. The mainstay of the US IGY rocket stable was the Aerobee Hi, which was modified and improved to create the Aerobee 150.
An Aerobee 150 rocket launched on June 12, 1962 detected the first X-rays from other celestial sources (Scorpius X-1).
USSR V-2 derivative launches
Starting on June 21, 1959 from Kapustin Yar, with a modified V-2 designated the R-5V, the USSR launched a series of four vehicles to detect solar X-rays: a R-2A on July 21, 1959 and two R-11A at 02:00 GMT and 14:00 GMT.Skylark
The British SkylarkSkylark (rocket)
Skylark was a British sounding rocket design. The Skylark was first launched in 1957 from Woomera, Australia and its 441st and final launch took place from Esrange, Sweden on 2 May 2005...
was probably the most successful of the many sounding rocket programs. The first launched in 1957 from Woomera
Woomera, South Australia
The town, or village, of Woomera is located in the south east corner of the Woomera Prohibited Area ; colloquially known as the Woomera Rocket Range...
, Australia and its 441st and final launch took place from Esrange
Esrange
Esrange Space Center is a rocket range and research centre located outside the town of Kiruna in northern Sweden. It is a base for scientific research with high altitude balloons, investigation of the aurora borealis, sounding rocket launches, and satellite tracking, among other things...
, Sweden on 2 May 2005. Launches were carried out from sites in Australia, Europe, and South America, with use by NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
, the European Space Research Organisation (ESRO
ESRO
The European Space Research Organization was an international organisation founded by 10 European nations with the intention of jointly pursuing scientific research in space. It was founded in 1964...
), and German
German Aerospace Center
The German Aerospace Center is the national centre for aerospace, energy and transportation research of the Federal Republic of Germany. It has multiple locations throughout Germany. Its headquarters are located in Cologne. It is engaged in a wide range of research and development projects in...
and Swedish
Swedish Space Corporation
The Swedish Space Corporation is a comprehensive space company covering the entire field, from the definition of innovative business concepts and space projects to the development, tests and operation of the systems....
space organizations. Skylark was used to obtain the first good-quality X-ray images of the solar corona.
The first X-ray surveys of the sky in the Southern Hemisphere were provided by Skylark launches. It was also used with high precision in September and October 1972 in an effort to locate the optical counterpart of X-ray source GX3+1 by lunar occultation.
Véronique
The French VéroniqueVéronique
Véronique is the designation of a French sounding rocket with liquid fuel drive that was developed partly by German scientists who worked in Peenemünde. The Véronique was built between 1950 and 1969 in several versions, of which the versions P2, P6 and R were only experimental models. They were...
was successfully launched on April 14, 1964 from Hammaguir
Hammaguir
Hammaguir is a town in Algeria, south-west of Béchar. Between 1947 and 1967 there was a rocket launch site near Hammaguir, used by France for launching sounding rockets and the satellite carrier "Diamant" between 1965 and 1967....
a, LC Blandine carrying experiments to measure UV and X-ray intensities and the FU110 to measure UV intensity from the atomic H
Hydrogen spectral series
The emission spectrum of atomic hydrogen is divided into a number of spectral series, with wavelengths given by the Rydberg formula. These observed spectral lines are due to electrons moving between energy levels in the atom. The spectral series are important in astronomy for detecting the presence...
(Lyman-α) line, and again on November 4, 1964.
Early satellites
The SOLar RADiation satellite program (SOLRAD) was conceived in the late 1950s to study the Sun's effects on Earth, particularly during periods of heightened solar activity. Solrad 1 was launched on June 22, 1960 aboard a Thor Able from Cape CanaveralCape Canaveral
Cape Canaveral, from the Spanish Cabo Cañaveral, is a headland in Brevard County, Florida, United States, near the center of the state's Atlantic coast. Known as Cape Kennedy from 1963 to 1973, it lies east of Merritt Island, separated from it by the Banana River.It is part of a region known as the...
at 1:54 a.m. EDT. As the world's first orbiting astronomical observatory, SOLRAD I determined that radio fade-outs were caused by solar X-ray emissions.
The first in a series of 8 successfully launched Orbiting Solar Observatories
Orbiting Solar Observatory
The Orbiting Solar Observatory Program was the name of a series of nine American science satellites primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully by NASA between 1962 and 1975 using Delta rockets...
(OSO 1, launched on March 7, 1963) had as its primary mission to measure solar electromagnetic radiation in the UV, X-ray, and gamma-ray regions.
The first USA satellite which detected cosmic X-rays was the Third Orbiting Solar Observatory, or OSO-3, launched on March 8, 1967. It was intended primarily to observe the Sun, which it did very well during its 2 year lifetime, but it also detected a flaring episode from the source Sco X-1 and measured the diffuse cosmic X-ray background.
OSO 5 was launched on January 22, 1969, and lasted until July 1975. It was the 5th satellite put into orbit as part of the Orbiting Solar Observatory
Orbiting Solar Observatory
The Orbiting Solar Observatory Program was the name of a series of nine American science satellites primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully by NASA between 1962 and 1975 using Delta rockets...
program. This program was intended to launch a series of nearly identical satellites to cover an entire 11-year solar cycle. The circular orbit had an altitude of 555 km and an inclination of 33°. The spin rate of the satellite was 1.8 s. The data produced a spectrum of the diffuse background over the energy range 14-200 keV.
OSO 6 was launched on August 9, 1969. Its orbital period was ~95 min. The spacecraft had a spin rate of 0.5 rps. On board was a hard X-ray detector (27-189 keV) with a 5.1 cm2 NaI(Tl) scintillator, collimated to 17° × 23° FWHM. The system had 4 energy channels (separated 27-49-75-118-189 keV). The detector spun with the spacecraft on a plane containing the Sun direction within ± 3.5°. Data were read with alternate 70 ms and 30 ms integrations for 5 intervals every 320 ms.
TD-1A
TD-1A
TD-1A, or Thor-Delta 1A, was a European astrophysical research satellite which was launched in 1972. Operated by the European Space Research Organisation, TD-1A made astronomical surveys primarily in the ultraviolet, but also using x-ray and gamma ray detectors.-Spacecraft:TD-1A was named after the...
was put in a nearly circular polar sun-synchronous orbit, with apogee 545 km, perigee 533 km, and inclination 97.6°. It was ESRO's first 3-axis stabilized satellite, with one axis pointing to the Sun to within ±5°. The optical axis was maintained perpendicular to the solar pointing axis and to the orbital plane. It scanned the entire celestial sphere every 6 months, with a great circle being scanned every satellite revolution. After about 2 months of operation, both of the satellite's tape recorders failed. A network of ground stations was put together so that real-time telemetry from the satellite was recorded for about 60% of the time. After 6 months in orbit, the satellite entered a period of regular eclipses as the satellite passed behind the Earth—cutting off sunlight to the solar panels. The satellite was put into hibernation for 4 months, until the eclipse period passed, after which systems were turned back on and another 6 months of observations were made. TD-1A
TD-1A
TD-1A, or Thor-Delta 1A, was a European astrophysical research satellite which was launched in 1972. Operated by the European Space Research Organisation, TD-1A made astronomical surveys primarily in the ultraviolet, but also using x-ray and gamma ray detectors.-Spacecraft:TD-1A was named after the...
was primarily a UV mission however it carried both a cosmic X-ray and a gamma-ray detector. TD-1A reentered on January 9, 1980.
Surveying and cataloging X-ray sources
OSO 7OSO 7
OSO 7 is the seventh in the series of American Orbiting Solar Observatory satellites launched by NASA between 1962 and 1975...
was primarily a solar observatory designed to point a battery of UV and X-ray telescopes at the Sun from a platform mounted on a cylindrical wheel. The detectors for observing cosmic X-ray sources were X-ray proportional counters. The hard X-ray telescope operated over the energy range 7 - 550 keV. OSO 7 performed an X-ray All-sky survey and discovered the 9-day periodicity in Vela X-1
Vela X-1
Vela X-1 is a pulsing, eclipsing high-mass X-ray binary system, associated with the Uhuru source 4U 0900-40 and the supergiant star HD 77581....
which led to its optical identification as a HMXRB. OSO 7 was launched on September 29, 1971 and operated until May 18, 1973.
Skylab
Skylab
Skylab was a space station launched and operated by NASA, the space agency of the United States. Skylab orbited the Earth from 1973 to 1979, and included a workshop, a solar observatory, and other systems. It was launched unmanned by a modified Saturn V rocket, with a mass of...
, a science and engineering laboratory, was launched into Earth orbit by a Saturn V rocket on May 14, 1973. Detailed X-ray studies of the Sun were performed. The S150 experiment performed a faint X-ray source survey. The S150 was mounted atop the SIV-B upper stage of the Saturn 1B rocket which orbited briefly behind and below Skylab on July 28, 1973. The entire SIV-B stage underwent a series of preprogrammed maneuvers, scanning about 1° every 15 seconds, to allow the instrument to sweep across selected regions of the sky. The pointing direction was determined during data processing, using the inertial guidance system of the SIV-B stage combined with information from two visible star sensors which formed part of the experiment. Galactic X-ray sources were observed with the S150 experiment. The experiment was designed to detect 4.0-10.0 nm photons. It consisted of a single large (~1500 cm2) proportional counter, electrically divided by fine wire ground planes into separate signal-collecting areas and looking through collimator vanes. The collimators defined 3 intersecting fields of view (~2 × 20°) on the sky, which allowed source positions to be determined to ~ 30'. The front window of the instrument consisted of a 2 µm thick plastic sheet. The counter gas was a mixture of argon and methane. Analysis of the data from the S150 experiment provided strong evidence that the soft X-ray background cannot be explained as the cumulative effect of many unresolved point sources.
Skylab's solar studies: UV and X-ray solar photography for highly ionized atoms, X-ray spectrography of solar flares and active regions, and X-ray emissions of lower solar corona.
Salyut 4
Salyut 4
Salyut 4 was a Salyut space station launched on December 26, 1974 into an orbit with an apogee of 355 km, a perigee of 343 km and an orbital inclination of 51.6 degrees. It was essentially a copy of the DOS 3, and unlike its ill-fated sibling it was a complete success...
space station was launched on December 26, 1974. It was in an orbit of 355 × 343 km, with an orbital period of 91.3 minutes, inclined at 51.6°. The X-ray telescope began observations on January 15, 1975.
Orbiting Solar Observatory (OSO 8) was launched on June 21, 1975. While OSO 8's primary objective was to observe the Sun, four instruments were dedicated to observations of other celestial X-ray sources brighter than a few milliCrab. A sensitivity of 0.001 of the Crab nebula source (= 1 "mCrab"). OSO 8 ceased operations on October 1, 1978.
X-ray source variability
Although several earlier X-ray observatories initiated the endeavor to study X-ray source variability, once the catalogs of X-ray sources were firmly established, more extensive studies could commence.Prognoz 6 carried two NaI(Tl) scintillators (2-511 keV, 2.2-98 keV), and a proportional counter
Proportional counter
A proportional counter is a measurement device to count particles of ionizing radiation and measure their energy.A proportional counter is a type of gaseous ionization detector. Its operation is similar to that of a Geiger-Müller counter, but uses a lower operating voltage. An inert gas is used to...
(2.2-7 keV) to study solar X-rays.
P78-1
P78-1 or Solwind was a United States satellite launched aboard an Atlas F rocket from Vandenberg Air Force Base in California on February 24, 1979. The satellite operated until September 13, 1985, when it was shot down in orbit by an F-15 Eagle fighter aircraft during an US Air Force ASM-135 ASAT...
or Solwind was launched on February 24, 1979 and continued operating until September 13, 1985, when it was shot down in orbit during an Air Force ASM-135 ASAT
ASM-135 ASAT
The ASM-135 ASAT is an air-launched anti-satellite multi stage missile that was developed by Ling-Temco-Vought'sLTV Aerospace division. The ASM-135 was carried exclusively by the United States Air Force 's F-15 Eagle fighter aircraft.-Development:...
test. The platform was of the Orbiting Solar Observatory (OSO) type, with a solar-oriented sail and a rotating wheel section. P78-1 was in a noon-midnight, Sun-synchronous orbit at 600 km altitude. The orbital inclination of 96° implied that a substantial fraction of the orbit was spent at high latitude, where the particle background prevented detector operation. In-flight experience showed that good data were obtained between 35° N and 35° S geomagnetic latitude outside the South Atlantic Anomaly. This yields an instrument duty cycle of 25-30%. Telemetry data were obtained for about 40-50% of the orbits, yielding a net data return of 10-15%. Though this data rate appears low, it means that about 108 seconds of good data reside in the XMON data base.
Data from the P78-1 X-Ray Monitor experiment offered source monitoring with a sensitivity comparable to that of instruments flown on SAS-3, OSO-8
Orbiting Solar Observatory
The Orbiting Solar Observatory Program was the name of a series of nine American science satellites primarily intended to study the Sun, though they also included important non-solar experiments. Eight were launched successfully by NASA between 1962 and 1975 using Delta rockets...
, or Hakucho
Hakucho
Hakucho was Japan's first X-ray astronomy satellite, developed by the Institute of Space and Aeronautical Science...
, and the advantages of longer observing times and unique temporal coverage. Five fields of inquiry were particularly well suited for investigation with P78-1 data:
- study of pulsational, eclipse, precession, and intrinsic source variability on time scales of tens of seconds to months in galactic X-ray sources.
- pulse timing studies of neutron stars.
- identification and study of new transient sources.
- observations of X-ray and gamma-ray bursts, and other fast transients.
- simultaneous X-ray coverage of objects observed by other satellites, such as HEAO-2 and 3, as well as bridging the gap in coverage of objects in the observational timeline.
Launched on February 21, 1981, the Hinotori satellite observations of the 1980s pioneered hard X-ray imaging of solar flares.
Tenma
Tenma
Tenma, known as Astro-B before launch, was Japan's second X-ray astronomy satellite, developed by the Institute of Space and Astronautical Science. It was launched on February 20, 1983 using a M-3S-3 rocket as the vehicle....
was the second Japanese X-ray astronomy satellite launched on February 20, 1983. Tenma carried GSFC
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...
detectors which had an improved energy resolution (by a factor of 2) compared to proportional counters and performed the first sensitive measurements of the iron spectral region for many astronomical objects. Energy range: 0.1-60 keV; gas scintillator proportional counter: 10 units of 80 cm2 each, FOV ~ 3° (FWHM), 2-60 keV; transient source monitor: 2-10 keV.
The Soviet Astron orbital station
Astron (spacecraft)
Astron was a Soviet spacecraft launched on 23 March 1983 at 12:45:06 UTC, using Proton launcher, which was designed to fulfill an astrophysics mission. It was based on the Venera spacecraft design and was operational for six years as the largest ultraviolet space telescope during its lifetime...
was designed primarily for UV and X-ray astrophysical observations. It was injected into orbit on March 23, 1983. The satellite was put into a highly elliptical orbit, ~200,000 × 2,000 km. The orbit kept the craft far away from the Earth for 3.5 out of every 4 days. It was outside of the Earth's shadow and radiation belts for 90% of the time. The second major experiment, SKR-02M, aboard Astron was an X-ray spectrometer, which consisted of a proportional counter sensitive to 2-25 keV X-rays, with an effective area of 0.17 m2. The FOV was 3° × 3° (FWHM). Data could be telemetered in 10 energy channels. The instrument began taking data on April 3, 1983.
Spacelab
Spacelab
Spacelab was a reusable laboratory used on certain spaceflights flown by the Space Shuttle. The laboratory consisted of multiple components, including a pressurized module, an unpressurized carrier and other related hardware housed in the Shuttle's cargo bay...
1 was the first Spacelab mission in orbit in the payload bay of the Space Shuttle (STS-9) between November 28 and December 8, 1983. An X-ray spectrometer, measuring 2-30 keV photons (although 2-80 keV was possible), was on the pallet. The primary science objective was to study detailed spectral features in cosmic sources and their temporal changes. The instrument was a gas scintillation proportional counter (GSPC) with ~ 180 cm2 area and energy resolution of 9% at 7 keV. The detector was collimated to a 4.5° (FWHM) FOV. There were 512 energy channels.
Spartan 1 was deployed from the Space Shuttle Discovery (STS-51G) on June 20, 1985 and retrieved 45.5 hours later. The X-ray detectors aboard the Spartan platform were sensitive to the energy range 1-12 keV. The instrument scanned its target with narrowly collimated (5' × 3°) GSPCs. There were 2 identical sets of counters, each having ~ 660 cm2 effective area. Counts were accumulated for 0.812 s into 128 energy channels. The energy resolution was 16% at 6 keV. During its 2 days of flight, Spartan-1 observed the Perseus cluster of galaxies and our galactic center region.
Ginga was launched on February 5, 1987. The primary instrument for observations was the Large Area Proportional Counter (LAC).
The European Retrievable Carrier (EURECA) was launched July 31, 1992 by the Space Shuttle Atlantis, and put into an orbit at an altitude of 508 km. It began its scientific mission on August 7, 1992. EURECA was retrieved on July 1, 1993 by the Space Shuttle Endeavor and returned to Earth. On board was the WATCH or Wide Angle Telescope for Cosmic Hard X-rays instrument. The WATCH instrument was sensitive to 6-150 keV photons. The total field of view covered 1/4 of the celestial sphere. During its 11 month lifetime, EURECA tracked the Sun and WATCH gradually scanned across the entire sky. Some 2 dozen known X-ray sources were monitored—some for more than 100 days—and a number of new X-ray transient
X-ray transient
X-ray emission occurs from many celestial objects. These emissions can have a pattern, occur intermittently, or as a transient astronomical event. In X-ray astronomy many sources have been discovered by placing an X-ray detector above the Earth's atmosphere. Often, the first X-ray source discovered...
s were discovered.
The Diffuse X-ray Spectrometer (DXS) STS-54
STS-54
-Mission parameters:*Mass:**Orbiter landing with payload: **Payload: *Perigee: *Apogee: *Inclination: 28.5°*Period: 90.6 min-Space walks:* Harbaugh and Runco – EVA 1*EVA 1 Start: 17 January 1993...
package was flown as an attached payload in January, 1993 to obtain spectra of the diffuse soft X-ray background. DXS obtained the first-ever high resolution spectra of the diffuse soft X-ray background in the energy band from 0.15 to 0.28 keV (4.3-8.4 nm).
X-1 X-ray sources
As all-sky surveys are performed and analyzed or once the first extrasolar X-ray source in each constellation is confirmed, it is designated X-1, e.g., Scorpius X-1Scorpius X-1
Scorpius X-1 is an X-ray source located roughly 9000 light years away in the constellation Scorpius. Scorpius X-1 was the first extrasolar X-ray source discovered, and, aside from the Sun, it is the strongest source of X-rays in the sky...
or Sco X-1. There are 88 official constellations. Often the first X-ray source is a transient.
As X-ray sources have been better located, many of them have been isolated to extragalactic regions such as the Large Magellanic Cloud (LMC). When there are often many individually discernible sources, the first one identified is usually designated as the extragalactic source X-1, e.g., Small Magellanic Cloud (SMC) X-1, a HMXRB, at 01h15m14s -73h42m22s.
These early X-ray sources still are studied and often produce significant results. For example, Serpens X-1.
As of August 27, 2007 discoveries concerning asymmetric iron line broadening and their implications for relativity have been a topic of much excitement. With respect to the asymmetric iron line broadening, Edward Cackett of the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
commented, "We're seeing the gas whipping around just outside the neutron star's surface,". "And since the inner part of the disk obviously can't orbit any closer than the neutron star's surface, these measurements give us a maximum size of the neutron star's diameter. The neutron stars can be no larger than 18 to 20.5 miles across, results that agree with other types of measurements."
"We've seen these asymmetric lines from many black holes, but this is the first confirmation that neutron stars can produce them as well. It shows that the way neutron stars accrete matter is not very different from that of black holes, and it gives us a new tool to probe Einstein's theory", says Tod Strohmayer of NASA
NASA
The National Aeronautics and Space Administration is the agency of the United States government that is responsible for the nation's civilian space program and for aeronautics and aerospace research...
's Goddard Space Flight Center
Goddard Space Flight Center
The Goddard Space Flight Center is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately northeast of Washington, D.C. in Greenbelt, Maryland, USA. GSFC,...
.
"This is fundamental physics", says Sudip Bhattacharyya also of NASA's in Greenbelt, Maryland
Greenbelt, Maryland
Greenbelt is a city in Prince George's County, Maryland, United States. Contained within today's City of Greenbelt is the historic planned community now known locally as "Old Greenbelt" and designated as the Greenbelt Historic District...
and the University of Maryland
University of Maryland
When the term "University of Maryland" is used without any qualification, it generally refers to the University of Maryland, College Park.University of Maryland may refer to the following:...
. "There could be exotic kinds of particles or states of matter, such as quark matter, in the centers of neutron stars, but it's impossible to create them in the lab. The only way to find out is to understand neutron stars."
Using XMM-Newton
XMM-Newton
The XMM-Newton is an orbiting X-ray observatory launched by ESA in December 1999 on a Ariane 5 rocket...
, Bhattacharyya and Strohmayer observed Serpens X-1, which contains a neutron star and a stellar companion. Cackett and Jon Miller of the University of Michigan
University of Michigan
The University of Michigan is a public research university located in Ann Arbor, Michigan in the United States. It is the state's oldest university and the flagship campus of the University of Michigan...
, along with Bhattacharyya and Strohmayer, used Suzaku
Suzaku
Suzaku may refer to:* Suzaku, the Japanese name for the Chinese Vermilion Bird , bird guardian of the South*Emperor Suzaku, emperor of Japan*SUZAK Inc., also known as Suzaku, a video game developer* Suzaku Avenue, one of the ancient main streets e.g...
's superb spectral capabilities to survey Serpens X-1. The Suzaku data confirmed the XMM-Newton result regarding the iron line in Serpens X-1.
X-ray source catalogs
Catalogs of X-ray sources have been put together for a variety of purposes including chronology of discovery, confirmation by X-ray flux measurement, initial detection, and X-ray source type.Sounding rocket X-ray source catalogs
One of the first catalogs of X-ray sources published came from workers at the US Naval Research Laboratory in 1966 and contained 35 X-ray sources. Of these only 22 had been confirmed by 1968. An additional astronomical catalog of discrete X-ray sources over the celestial sphereCelestial sphere
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with the Earth and rotating upon the same axis. All objects in the sky can be thought of as projected upon the celestial sphere. Projected upward from Earth's equator and poles are the...
by constellation
Constellation
In modern astronomy, a constellation is an internationally defined area of the celestial sphere. These areas are grouped around asterisms, patterns formed by prominent stars within apparent proximity to one another on Earth's night sky....
contains 59 sources as of December 1, 1969, that at the least had an X-ray flux published in the literature.
Early X-ray observatory satellite catalogs
Each of the major observatory satellites had its own catalog of detected and observed X-ray sources. These catalogs were often the result of large area sky surveys. Many of the X-ray sources have names that come from a combination of a catalog abbreviation and the Right AscensionRight ascension
Right ascension is the astronomical term for one of the two coordinates of a point on the celestial sphere when using the equatorial coordinate system. The other coordinate is the declination.-Explanation:...
(RA) and Declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
(Dec) of the object. For example, 4U 0115+63, 4th Uhuru
Uhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
catalog, RA=01 hr 15 min, Dec=+63°; 3S 1820-30 is the SAS-3 catalog; EXO 0748-676 is an Exosat
EXOSAT
The European X-ray Observatory Satellite , originally named HELOS, was operational from May 1983 until April 1986 and in that time made 1780 observations in the X-ray band of most classes of astronomical object including active galactic nuclei, stellar coronae, cataclysmic variables, white dwarfs,...
catalog entry; HEAO 1 uses H; Ariel 5 is 3A; Ginga sources are in GS; general X-ray sources are in the X catalog. Of the early satellites, the Vela
Vela (satellite)
Vela was the name of a group of satellites developed as the Vela Hotel element of Project Vela by the United States to monitor compliance with the 1963 Partial Test Ban Treaty by the Soviet Union, and other nuclear-capable states. It means vigil or "watch" in Spanish.Vela started out as a small...
series X-ray sources have been cataloged.
The Uhuru
Uhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
X-ray satellite made extensive observations and produced at least 4 catalogs wherein previous catalog designations were improved and relisted: 1ASE or 2ASE 1615+38 would appear successively as 2U 1615+38, 3U 1615+38, and 4U 1615+3802, for example. After over a year of initial operation the first catalog (2U) was produced. The third Uhuru
Uhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
catalog was published in 1974. The fourth and final Uhuru catalog included 339 sources.
Although apparently not containing extrasolar sources from the earlier OSO satellites, the MIT/OSO 7 catalog contains 185 sources from the OSO 7
OSO 7
OSO 7 is the seventh in the series of American Orbiting Solar Observatory satellites launched by NASA between 1962 and 1975...
detectors and sources from the 3U catalog.
The 3rd Ariel 5 SSI Catalog (designated 3A) contains a list of X-ray sources detected by the University of Leicester's Sky Survey Instrument (SSI) on the Ariel 5 satellite. This catalog contains both low and high galactic latitude sources and includes some sources observed by HEAO 1, Einstein
Einstein Observatory
Einstein Observatory was the first fully imaging X-ray telescope put into space and the second of NASA's three High Energy Astrophysical Observatories...
, OSO 7
OSO 7
OSO 7 is the seventh in the series of American Orbiting Solar Observatory satellites launched by NASA between 1962 and 1975...
, SAS 3, Uhuru
Uhuru (satellite)
Uhuru was the first satellite launched specifically for the purpose of X-ray astronomy. It was also known as the X-ray Explorer Satellite, SAS-A , SAS 1, or Explorer 42.The observatory was launched on 12 December 1970 into an initial orbit of about 560 km apogee, 520 km...
, and earlier, mainly rocket, observations. The second Ariel catalog (designated 2A) contains 105 X-ray sources observed before April 1, 1977. Prior to 2A some sources were observed that may not have been included.
The 842 sources in the HEAO A-1 X-ray source catalog were detected with the NRL Large Area Sky Survey Experiment on the HEAO 1 satellite.
When EXOSAT
EXOSAT
The European X-ray Observatory Satellite , originally named HELOS, was operational from May 1983 until April 1986 and in that time made 1780 observations in the X-ray band of most classes of astronomical object including active galactic nuclei, stellar coronae, cataclysmic variables, white dwarfs,...
was slewing between different pointed observations from 1983 to 1986, it scanned a number of X-ray sources (1210). From this the EXOSAT Medium Energy Slew Survey catalog was created. From the use of the Gas Scintillation Proportional Counter (GSPC) on board EXOSAT, a catalog of iron lines from some 431 sources was made available.
Specialty and all-sky survey X-ray source catalogs
The Catalog of High-Mass X-ray Binaries in the Galaxy (4th Ed.) contains source name(s), coordinates, finding charts, X-ray luminosities, system parameters, and stellar parameters of the components and other characteristic properties for 114 HMXBs, together with a comprehensive selection of the relevant literature. About 60% of the high-mass X-ray binary candidates are known or suspected Be/X-ray binariesBe X-ray binaries
Be X-ray binaries are a class of high-mass X-ray binaries that consist of a Be star and a neutron star. The neutron star is usually in a wide highly elliptical orbit around the Be star. The Be stellar wind forms a disk confined to a plane often different from the orbital plane of the neutron star...
, while 32% are supergiant/X-ray binaries (SGXB).
For all the main-sequence and subgiant stars of spectral types A, F, G, and K and luminosity classes IV and V listed in the Bright Star Catalogue (BSC, also known as the HR Catalogue) that have been detected as X-ray sources in the ROSAT All-Sky Survey (RASS), there is the RASSDWARF - RASS A-K Dwarfs/Subgiants Catalog. The total number of RASS sources amounts to ~150,000 and in the BSC 3054 late-type main-sequence and subgiant stars of which 980 are in the catalog, with a chance coincidence of 2.2% (21.8 of 980).
See also
- Ultraviolet astronomy
- X-ray astronomyX-ray astronomyX-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and...
- Gamma-ray astronomyGamma-ray astronomyGamma-ray astronomy is the astronomical study of the cosmos with gamma rays. Gamma-rays are the most energetic form of "light" that travel across the universe, and gamma-rays thus have the smallest wavelength of any wave in the electromagnetic spectrum.Gamma-rays are created by celestial events...
- X-1 X-ray source
- Sounding rocket X-ray astronomy
- X-ray astronomy satellitesX-ray astronomy satellitesX-ray astronomy satellites study X-ray emissions from celestial objects. Satellites, which can detect and transmit data about the X-ray emissions are deployed as part of branch of space science known as X-ray astronomy...
- Stellar X-ray astronomy
- Solar X-ray astronomy
- X-ray telescopeX-ray telescopeAn X-ray telescope is a telescope that is designed to observe remote objects in the X-ray spectrum. In order to get above the Earth's atmosphere, which is opaque to X-rays, X-ray telescopes must be mounted on high altitude rockets or artificial satellites.-Optical design:X-ray telescopes can use...
- Astronomical X-ray source catalog