Kepler-4b
Encyclopedia
Kepler-4b, initially known as KOI 7.01, is an extrasolar planet first detected as a transit
by the Kepler spacecraft. Its radius
and mass
are similar to that of Neptune
; however, due to its proximity to its host star, it is substantially hotter than any planet in the Solar System. The planet's discovery was announced on January 4, 2010 in Washington, D.C.
along with four other planets that were initially detected by the Kepler spacecraft and subsequently confirmed by telescopes at the W.M. Keck Observatory.
. The star was, in turn, named for the Kepler Mission, a NASA
satellite whose purpose is to discover Earth-like planets in a section of the sky between constellations Cygnus and Lyra
using the transit method. Using this method, Kepler notes small and steady decreases in a star's brightness that are measured as a planet crosses in front of it. Initially, Kepler-4b was detected as a transit event by the Kepler telescope and considered a Kepler Object of Interest
with the designation KOI 7.01.
Subsequent radial velocity
measurements by the High Resolution Echelle Spectrometer on the telescopes of W.M. Keck Observatory confirmed the planetary nature of the transit event and established a mass estimate for the planet. The planet's existence was announced on January 4, 2010 along with four other planets detected by Kepler: Kepler-5b
, 6b
, 7b
and 8b
at the 215th meeting of the American Astronomical Society
in Washington, D.C.
on the sky, and is approximately 550 parsecs from our solar system. It has an effective temperature almost identical to the Sun
at 5857 Kelvin
, but a mass and radius that are somewhat larger than the sun: respectively, 1.223
and 1.487
. The star is thought to be around 4.5 billion years old, and at or very near the end of its main-sequence hydrogen burning phase. In several tens of millions of years it will likely become a subgiant star.
. This places it almost 10 times closer to its star than Mercury is to the Sun. Consequently, Kepler-4b is thought to be extremely hot, with an equilibrium temperature greater than 1700 Kelvin
(2600 Fahrenheit). The planet is estimated to be 25 times more massive than the Earth with a radius that is 4 times greater than the Earth. This makes it similar to Neptune in terms of size and mass, but with a temperature that is not comparable to any planet in our solar system (Venus, the hottest planet is only 735 Kelvin).
Astronomical transit
The term transit or astronomical transit has three meanings in astronomy:* A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, hiding a small part of it, as seen by an observer at some particular vantage point...
by the Kepler spacecraft. Its radius
Radius
In classical geometry, a radius of a circle or sphere is any line segment from its center to its perimeter. By extension, the radius of a circle or sphere is the length of any such segment, which is half the diameter. If the object does not have an obvious center, the term may refer to its...
and mass
Mass
Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...
are similar to that of Neptune
Neptune
Neptune is the eighth and farthest planet from the Sun in the Solar System. Named for the Roman god of the sea, it is the fourth-largest planet by diameter and the third largest by mass. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times...
; however, due to its proximity to its host star, it is substantially hotter than any planet in the Solar System. The planet's discovery was announced on January 4, 2010 in Washington, D.C.
Washington, D.C.
Washington, D.C., formally the District of Columbia and commonly referred to as Washington, "the District", or simply D.C., is the capital of the United States. On July 16, 1790, the United States Congress approved the creation of a permanent national capital as permitted by the U.S. Constitution....
along with four other planets that were initially detected by the Kepler spacecraft and subsequently confirmed by telescopes at the W.M. Keck Observatory.
Nomenclature and history
Kepler-4b was named because it was the first planet discovered in the orbit of its star, Kepler-4Kepler-4
Kepler-4 is a sunlike star located about 1631 light-years away in the constellation Draco. It is in the field of view of the Kepler Mission, a NASA operation purposed with finding Earth-like planets. Kepler-4b, a Neptune-sized planet that orbits extremely close to its star, was discovered in its...
. The star was, in turn, named for the Kepler Mission, a 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...
satellite whose purpose is to discover Earth-like planets in a section of the sky between constellations Cygnus and Lyra
Lyra
Lyra is a small constellation. It is one of the 48 constellations listed by the 2nd century astronomer Ptolemy, and remains one of the 88 modern constellations recognized by the International Astronomical Union. Its principal star, Vega — a corner of the Summer Triangle — is one of the brightest...
using the transit method. Using this method, Kepler notes small and steady decreases in a star's brightness that are measured as a planet crosses in front of it. Initially, Kepler-4b was detected as a transit event by the Kepler telescope and considered a Kepler Object of Interest
Kepler Object of Interest
A Kepler Object of Interest is a star observed by the Kepler spacecraft which is suspected of hosting one or more transiting planets. KOIs come from a master list of 150,000 stars which itself is generated from the Kepler Input Catalog . A KOI shows a periodic dimming, indicative of an unseen...
with the designation KOI 7.01.
Subsequent radial velocity
Radial velocity
Radial velocity is the velocity of an object in the direction of the line of sight . In astronomy, radial velocity most commonly refers to the spectroscopic radial velocity...
measurements by the High Resolution Echelle Spectrometer on the telescopes of W.M. Keck Observatory confirmed the planetary nature of the transit event and established a mass estimate for the planet. The planet's existence was announced on January 4, 2010 along with four other planets detected by Kepler: Kepler-5b
Kepler-5b
Kepler-5b is one of the first five planets discovered by NASA's Kepler spacecraft. It is a Hot Jupiter that orbits a subgiant star that is more massive, larger, and more diffuse than the Sun is...
, 6b
Kepler-6b
Kepler-6b is an extrasolar planet in the orbit of the unusually metal-rich Kepler-6, a star in the field of view of the NASA-operated Kepler spacecraft, which searches for planets that cross directly in front of, or transit, their host stars. It was the third planet to be discovered by Kepler....
, 7b
Kepler-7b
Kepler-7b is one of the first five planets to be confirmed by NASA's Kepler spacecraft, and was confirmed in the first 33.5 days of Kepler's science operations. It is in the orbit of a star that is not as hot as the Sun, but is significantly larger and is expected to soon reach the end of the main...
and 8b
Kepler-8b
Kepler-8b is the fifth of the first five exoplanets discovered by NASA's Kepler spacecraft, which aims to discover planets in a region of the sky between the constellations Lyra and Cygnus that transit their host stars. The planet is the hottest of the five...
at the 215th meeting of the American Astronomical Society
American Astronomical Society
The American Astronomical Society is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC...
in Washington, D.C.
Host star
Kepler-4 is located within the Draco constellationDraco (constellation)
Draco is a constellation in the far northern sky. Its name is Latin for dragon. Draco is circumpolar for many observers in the northern hemisphere...
on the sky, and is approximately 550 parsecs from our solar system. It has an effective temperature almost identical to the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
at 5857 Kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
, but a mass and radius that are somewhat larger than the sun: respectively, 1.223
Solar mass
The solar mass , , is a standard unit of mass in astronomy, used to indicate the masses of other stars and galaxies...
and 1.487
. The star is thought to be around 4.5 billion years old, and at or very near the end of its main-sequence hydrogen burning phase. In several tens of millions of years it will likely become a subgiant star.Characteristics
Kepler-4b orbits its host star in 3.213 days at a distance of 0.046 AUAstronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
. This places it almost 10 times closer to its star than Mercury is to the Sun. Consequently, Kepler-4b is thought to be extremely hot, with an equilibrium temperature greater than 1700 Kelvin
Kelvin
The kelvin is a unit of measurement for temperature. It is one of the seven base units in the International System of Units and is assigned the unit symbol K. The Kelvin scale is an absolute, thermodynamic temperature scale using as its null point absolute zero, the temperature at which all...
(2600 Fahrenheit). The planet is estimated to be 25 times more massive than the Earth with a radius that is 4 times greater than the Earth. This makes it similar to Neptune in terms of size and mass, but with a temperature that is not comparable to any planet in our solar system (Venus, the hottest planet is only 735 Kelvin).
See also
- Kepler-5bKepler-5bKepler-5b is one of the first five planets discovered by NASA's Kepler spacecraft. It is a Hot Jupiter that orbits a subgiant star that is more massive, larger, and more diffuse than the Sun is...
- Kepler-6bKepler-6bKepler-6b is an extrasolar planet in the orbit of the unusually metal-rich Kepler-6, a star in the field of view of the NASA-operated Kepler spacecraft, which searches for planets that cross directly in front of, or transit, their host stars. It was the third planet to be discovered by Kepler....
- Kepler-7bKepler-7bKepler-7b is one of the first five planets to be confirmed by NASA's Kepler spacecraft, and was confirmed in the first 33.5 days of Kepler's science operations. It is in the orbit of a star that is not as hot as the Sun, but is significantly larger and is expected to soon reach the end of the main...
- Kepler-8bKepler-8bKepler-8b is the fifth of the first five exoplanets discovered by NASA's Kepler spacecraft, which aims to discover planets in a region of the sky between the constellations Lyra and Cygnus that transit their host stars. The planet is the hottest of the five...
- Kepler-9bKepler-9bKepler-9b is one of the first planets discovered outside the solar system by NASA's Kepler Mission. It revolves around the star Kepler-9 within the constellation Lyra. Kepler-9b is the largest of three planets detected in the Kepler system by transit method; its mass is slightly smaller than the...
- Kepler-10bKepler-10bKepler-10b is the first confirmed terrestrial planet to have been discovered outside the Solar System. Discovered after several months of data collection during the course of the NASA-directed Kepler Mission, which aims to discover Earth-like planets crossing in front of their host stars, the...
External links
- http://kepler.nasa.gov/Mission/discoveries/kepler4b/