OGLE-2005-BLG-390Lb
Encyclopedia
OGLE-2005-BLG-390Lb is a 'super-Earth
' extrasolar planet
orbiting the star
OGLE-2005-BLG-390L
, which is situated 21,500 ±
3,300 light years away from Earth, near the center of the Milky Way
galaxy
. On January 25, 2006, Probing Lensing Anomalies NETwork
/Robotic Telescope Network (PLANET/Robonet), Optical Gravitational Lensing Experiment
(OGLE), and Microlensing Observations in Astrophysics
(MOA) made a joint announcement of the discovery. The planet does not appear to meet conditions presumed necessary to support life
.
s around its star at an average distance of 2.0 to 4.1 AU
, or an orbit that would fall between the orbits of Mars
and Jupiter
in our own solar system. (This range of distances is the range of error in measurement and calculation; it does not represent the planet's orbital eccentricity, as its orbital elements are not known.) Until this discovery, no small exoplanet had been found farther than 0.15 AUs from a main sequence
star. The planet takes approximately 10 Earth years to orbit its star, OGLE-2005-BLG-390L
.
OGLE-2005-BLG-390Lb's sun (located in the constellation Scorpius
, RA
17:54:19.2, Dec
−30°22′38″, J2000
, 6.6 ± 1.0 kpc
distance) is thought to likely be a cool red dwarf
(95% probability), or a white dwarf
(4% probability), with a very slight chance that it is a neutron star
or black hole
(<1% probability). Regardless of the star's classification, its radiant energy output would be significantly less than that of the Sun
.
The planet is estimated to be about five times Earth's mass (5.5 ME
). Some astronomers have speculated that it may have a rocky core
like Earth, with a thin atmosphere
. Its distance from the star, and the star's relatively low temperature, means that the planet's likely surface temperature is around 50 K (-223.2 °C; -369.7 °F). If it is a rocky world, this temperature would make it likely that the surface would be made of frozen volatiles
, substances which would be liquids or gases on Earth: water, ammonia
, methane
and nitrogen
would all be frozen solid. If it is not a rocky planet, it would more closely resemble an icy gas planet like Uranus
, although much smaller.
The planet is not so much notable for its size, or possible composition — although these are unusual — but for the fact that such a relatively small exoplanet was detected at such a relatively large distance from its star. Prior to this, "small" exoplanets, such as Gliese 876 d
which has a "year" of less than 2 Earth-days, were detected very close to their stars. OGLE-2005-BLG-390Lb shows a combination of size and orbit which would not make it out of place in Earth's own solar system
.
"The team has discovered the most Earthlike planet yet," said Michael Turner, assistant director for the mathematical and physical sciences directorate at the National Science Foundation
, which supported the work. At 5.5 Earth masses, the planet is less massive than the previous candidate for lowest-mass extrasolar planet around a main sequence star, the 7.5 Earth mass Gliese 876 d. Although Earth-sized or smaller planets have been detected, as of January 2006, they have only been found orbiting millisecond pulsar
s like PSR B1257+12.
1.54-m telescope at ESO
La Silla Observatory
in Chile
. The telescope was part of a network of telescopes used by the PLANET
/RoboNet gravitational microlensing campaign. Much of the follow-up observational data was gathered by a 0.6-m telescope at the Perth Observatory
in Western Australia.
Gravitational lensing occurs when light from a distant star is bent and magnified by the gravitational field of a foreground star. A gravitational microlensing
event occurs when a planet accompanying this foreground star can cause an additional small increase in the intensity of magnified light as it passes between the background star and the observer as well.
The PLANET
/RoboNet campaign regularly investigates promising microlensing
event alerts that are issued by the Polish
OGLE
or the Japanese-New Zealand MOA
survey. The observation of just such an event led to the discovery of OGLE-2005-BLG-390Lb. OGLE
detected the microlensing effect produced by the star OGLE-2005-BLG-390L
, and it was the PLANET
team's follow up observations and analysis which uncovered evidence of the planet itself.
The PLANET team conducted close observation of the OGLE-2005-BLG-390 microlensing event over a period of about two weeks. During this series of observations, a 15% "spike" in intensity occurred, lasting approximately 12 hours. From the intensity of the increase, and its length, the PLANET astronomers were able to derive the planet's mass, and its approximate displacement from the star.
The paper submitted to Nature
bears the names of all members of PLANET
, RoboNet
, OGLE
, and MOA
.
Super-Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's gas giants. The term super-Earth refers only to the mass of the planet, and does not imply anything about the surface conditions or habitability...
' extrasolar planet
Extrasolar planet
An extrasolar planet, or exoplanet, is a planet outside the Solar System. A total of such planets have been identified as of . It is now known that a substantial fraction of stars have planets, including perhaps half of all Sun-like stars...
orbiting the star
Star
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
OGLE-2005-BLG-390L
OGLE-2005-BLG-390L
OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star (95% probability, 4% probability it is a white dwarf,...
, which is situated 21,500 ±
Plus-minus sign
The plus-minus sign is a mathematical symbol commonly used either*to indicate the precision of an approximation, or*to indicate a value that can be of either sign....
3,300 light years away from Earth, near the center of the Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
. On January 25, 2006, Probing Lensing Anomalies NETwork
Probing Lensing Anomalies Network
The Probing Lensing Anomalies NETwork collaboration coordinates a network of telescopes to rapidly sample photometric measurements of the magnification of stars in the galactic bulge undergoing gravitational microlensing by intervening foreground stars...
/Robotic Telescope Network (PLANET/Robonet), Optical Gravitational Lensing Experiment
Optical Gravitational Lensing Experiment
The Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side...
(OGLE), and Microlensing Observations in Astrophysics
Microlensing Observations in Astrophysics
Microlensing Observations in Astrophysics is a collaborative project between researchers in New Zealand and Japan, led by Professor Yasushi Muraki of Nagoya University. They use microlensing to observe dark matter, extra-solar planets, and stellar atmospheres from the Southern Hemisphere...
(MOA) made a joint announcement of the discovery. The planet does not appear to meet conditions presumed necessary to support life
Planetary habitability
Planetary habitability is the measure of a planet's or a natural satellite's potential to sustain life. Life may develop directly on a planet or satellite or be transferred to it from another body, a theoretical process known as panspermia...
.
Physical characteristics
OGLE-2005-BLG-390Lb orbitOrbit
In physics, an orbit is the gravitationally curved path of an object around a point in space, for example the orbit of a planet around the center of a star system, such as the Solar System...
s around its star at an average distance of 2.0 to 4.1 AU
Astronomical unit
An astronomical unit is a unit of length equal to about or approximately the mean Earth–Sun distance....
, or an orbit that would fall between the orbits of Mars
Mars
Mars is the fourth planet from the Sun in the Solar System. The planet is named after the Roman god of war, Mars. It is often described as the "Red Planet", as the iron oxide prevalent on its surface gives it a reddish appearance...
and Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
in our own solar system. (This range of distances is the range of error in measurement and calculation; it does not represent the planet's orbital eccentricity, as its orbital elements are not known.) Until this discovery, no small exoplanet had been found farther than 0.15 AUs from a main sequence
Main sequence
The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. These color-magnitude plots are known as Hertzsprung–Russell diagrams after their co-developers, Ejnar Hertzsprung and Henry Norris Russell...
star. The planet takes approximately 10 Earth years to orbit its star, OGLE-2005-BLG-390L
OGLE-2005-BLG-390L
OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star (95% probability, 4% probability it is a white dwarf,...
.
OGLE-2005-BLG-390Lb's sun (located 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...
, RA
Right 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:...
17:54:19.2, Dec
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...
−30°22′38″, J2000
Epoch (astronomy)
In astronomy, an epoch is a moment in time used as a reference point for some time-varying astronomical quantity, such as celestial coordinates, or elliptical orbital elements of a celestial body, where these are subject to perturbations and vary with time...
, 6.6 ± 1.0 kpc
Parsec
The parsec is a unit of length used in astronomy. It is about 3.26 light-years, or just under 31 trillion kilometres ....
distance) is thought to likely be a cool red dwarf
Red dwarf
According to the Hertzsprung-Russell diagram, a red dwarf star is a small and relatively cool star, of the main sequence, either late K or M spectral type....
(95% probability), or a white dwarf
White dwarf
A white dwarf, also called a degenerate dwarf, is a small star composed mostly of electron-degenerate matter. They are very dense; a white dwarf's mass is comparable to that of the Sun and its volume is comparable to that of the Earth. Its faint luminosity comes from the emission of stored...
(4% probability), with a very slight chance that it is 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...
or black hole
Black hole
A black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
(<1% probability). Regardless of the star's classification, its radiant energy output would be significantly less than that of 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...
.
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...
). Some astronomers have speculated that it may have a rocky core
Planetary core
The planetary core consists of the innermost layer of a planet.The core may be composed of solid and liquid layers, while the cores of Mars and Venus are thought to be completely solid as they lack an internally generated magnetic field. In our solar system, core size can range from about 20% to...
like Earth, with a thin atmosphere
Atmosphere
An atmosphere is a layer of gases that may surround a material body of sufficient mass, and that is held in place by the gravity of the body. An atmosphere may be retained for a longer duration, if the gravity is high and the atmosphere's temperature is low...
. Its distance from the star, and the star's relatively low temperature, means that the planet's likely surface temperature is around 50 K (-223.2 °C; -369.7 °F). If it is a rocky world, this temperature would make it likely that the surface would be made of frozen volatiles
Volatiles
In planetary science, volatiles are that group of chemical elements and chemical compounds with low boiling points that are associated with a planet's or moon's crust and/or atmosphere. Examples include nitrogen, water, carbon dioxide, ammonia, hydrogen, and methane, all compounds of C, H, O...
, substances which would be liquids or gases on Earth: water, ammonia
Ammonia
Ammonia is a compound of nitrogen and hydrogen with the formula . It is a colourless gas with a characteristic pungent odour. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to food and fertilizers. Ammonia, either directly or...
, methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
and nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
would all be frozen solid. If it is not a rocky planet, it would more closely resemble an icy gas planet like Uranus
Uranus
Uranus is the seventh planet from the Sun. It has the third-largest planetary radius and fourth-largest planetary mass in the Solar System. It is named after the ancient Greek deity of the sky Uranus , the father of Cronus and grandfather of Zeus...
, although much smaller.
The planet is not so much notable for its size, or possible composition — although these are unusual — but for the fact that such a relatively small exoplanet was detected at such a relatively large distance from its star. Prior to this, "small" exoplanets, such as Gliese 876 d
Gliese 876 d
Gliese 876 d is an extrasolar planet approximately 15 light-years away in the constellation of Aquarius . The planet was the third planet discovered orbiting the red dwarf star Gliese 876. At the time of its discovery, the planet had the lowest mass of any known extrasolar planet apart from the...
which has a "year" of less than 2 Earth-days, were detected very close to their stars. OGLE-2005-BLG-390Lb shows a combination of size and orbit which would not make it out of place in Earth's own solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
.
"The team has discovered the most Earthlike planet yet," said Michael Turner, assistant director for the mathematical and physical sciences directorate at the National Science Foundation
National Science Foundation
The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...
, which supported the work. At 5.5 Earth masses, the planet is less massive than the previous candidate for lowest-mass extrasolar planet around a main sequence star, the 7.5 Earth mass Gliese 876 d. Although Earth-sized or smaller planets have been detected, as of January 2006, they have only been found orbiting millisecond pulsar
Millisecond pulsar
A millisecond pulsar is a pulsar with a rotational period in the range of about 1-10 milliseconds. Millisecond pulsars have been detected in the radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The origin of millisecond pulsars is still unknown...
s like PSR B1257+12.
Discovery
OGLE-2005-BLG-390Lb's signature was first detected on August 10, 2005 by observations at the DanishDenmark
Denmark is a Scandinavian country in Northern Europe. The countries of Denmark and Greenland, as well as the Faroe Islands, constitute the Kingdom of Denmark . It is the southernmost of the Nordic countries, southwest of Sweden and south of Norway, and bordered to the south by Germany. Denmark...
1.54-m telescope at ESO
ESO
ESO, as a three-letter abbreviation, may stand for:* European Southern Observatory* Ensemble Studios Online* English Symphony Orchestra* Edmonton Symphony Orchestra* Executive Stock Options...
La Silla Observatory
La Silla Observatory
La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory organisation, and several others are partly maintained by ESO...
in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. The telescope was part of a network of telescopes used by the PLANET
Probing Lensing Anomalies Network
The Probing Lensing Anomalies NETwork collaboration coordinates a network of telescopes to rapidly sample photometric measurements of the magnification of stars in the galactic bulge undergoing gravitational microlensing by intervening foreground stars...
/RoboNet gravitational microlensing campaign. Much of the follow-up observational data was gathered by a 0.6-m telescope at the Perth Observatory
Perth Observatory
The Perth Observatory is the name of two astronomical observatories located in Western Australia.-First Perth Observatory:The original Perth Observatory was constructed in 1896 and was officially opened in 1900 by John Forrest, the first premier of Western Australia. The observatory was located at...
in Western Australia.
Gravitational lensing occurs when light from a distant star is bent and magnified by the gravitational field of a foreground star. A gravitational microlensing
Gravitational microlensing
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects ranging from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers can only detect bright objects that emit lots of light ...
event occurs when a planet accompanying this foreground star can cause an additional small increase in the intensity of magnified light as it passes between the background star and the observer as well.
The PLANET
Probing Lensing Anomalies Network
The Probing Lensing Anomalies NETwork collaboration coordinates a network of telescopes to rapidly sample photometric measurements of the magnification of stars in the galactic bulge undergoing gravitational microlensing by intervening foreground stars...
/RoboNet campaign regularly investigates promising microlensing
Gravitational microlensing
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects ranging from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers can only detect bright objects that emit lots of light ...
event alerts that are issued by the Polish
Poland
Poland , officially the Republic of Poland , is a country in Central Europe bordered by Germany to the west; the Czech Republic and Slovakia to the south; Ukraine, Belarus and Lithuania to the east; and the Baltic Sea and Kaliningrad Oblast, a Russian exclave, to the north...
OGLE
Optical Gravitational Lensing Experiment
The Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side...
or the Japanese-New Zealand MOA
Microlensing Observations in Astrophysics
Microlensing Observations in Astrophysics is a collaborative project between researchers in New Zealand and Japan, led by Professor Yasushi Muraki of Nagoya University. They use microlensing to observe dark matter, extra-solar planets, and stellar atmospheres from the Southern Hemisphere...
survey. The observation of just such an event led to the discovery of OGLE-2005-BLG-390Lb. OGLE
Optical Gravitational Lensing Experiment
The Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side...
detected the microlensing effect produced by the star OGLE-2005-BLG-390L
OGLE-2005-BLG-390L
OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star OGLE-2005-BLG-390L is a star thought to be a spectral type M - red dwarf star (95% probability, 4% probability it is a white dwarf,...
, and it was the PLANET
Probing Lensing Anomalies Network
The Probing Lensing Anomalies NETwork collaboration coordinates a network of telescopes to rapidly sample photometric measurements of the magnification of stars in the galactic bulge undergoing gravitational microlensing by intervening foreground stars...
team's follow up observations and analysis which uncovered evidence of the planet itself.
The PLANET team conducted close observation of the OGLE-2005-BLG-390 microlensing event over a period of about two weeks. During this series of observations, a 15% "spike" in intensity occurred, lasting approximately 12 hours. From the intensity of the increase, and its length, the PLANET astronomers were able to derive the planet's mass, and its approximate displacement from the star.
The paper submitted to Nature
Nature (journal)
Nature, first published on 4 November 1869, is ranked the world's most cited interdisciplinary scientific journal by the Science Edition of the 2010 Journal Citation Reports...
bears the names of all members of PLANET
Probing Lensing Anomalies Network
The Probing Lensing Anomalies NETwork collaboration coordinates a network of telescopes to rapidly sample photometric measurements of the magnification of stars in the galactic bulge undergoing gravitational microlensing by intervening foreground stars...
, RoboNet
RoboNet
RoboNet-1.0 was a prototype global network of UK-built 2-metre robotic telescopes, the largest of their kind in the world, comprising the Liverpool Telescope on La Palma , the Faulkes Telescope North on Maui , and the Faulkes Telescope South in Australia, managed by a consortium of ten UK...
, OGLE
Optical Gravitational Lensing Experiment
The Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side...
, and MOA
Microlensing Observations in Astrophysics
Microlensing Observations in Astrophysics is a collaborative project between researchers in New Zealand and Japan, led by Professor Yasushi Muraki of Nagoya University. They use microlensing to observe dark matter, extra-solar planets, and stellar atmospheres from the Southern Hemisphere...
.
See also
- Gliese 581 cGliese 581 cGliese 581 c or Gl 581 c is a planet orbiting the red dwarf star Gliese 581. It is the second planet discovered in the system and the third in order from the star. With a mass at least 5.6 times that of the Earth, it is classified as a super-Earth...
- Gliese 581 gGliese 581 gGliese 581 g , also Gl 581 g or GJ 581 g, is a hypothesized extrasolar planet proven nonexistent by the Geneva Team, orbiting the red dwarf star Gliese 581, 20.5 light-years from Earth in the constellation of Libra. It is the sixth planet discovered in the Gliese 581 planetary system and the fourth...
- OGLE-2005-BLG-169LbOGLE-2005-BLG-169LbOGLE-2005-BLG-169Lb is an extrasolar planet located approximately 2700 parsecs away in the constellation of Sagittarius, orbiting the star OGLE-2005-BLG-169L. This planet was discovered by the OGLE project using the gravitational microlensing method. Based on a most likely mass for the host star of...
- Optical Gravitational Lensing ExperimentOptical Gravitational Lensing ExperimentThe Optical Gravitational Lensing Experiment or OGLE is a Polish astronomical project based at the University of Warsaw that is chiefly concerned with discovering dark matter using the microlensing technique. Since the project began in 1992, it has discovered several extrasolar planets as a side...
(OGLE) - Planetary habitabilityPlanetary habitabilityPlanetary habitability is the measure of a planet's or a natural satellite's potential to sustain life. Life may develop directly on a planet or satellite or be transferred to it from another body, a theoretical process known as panspermia...