NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeedin ...
) is a
super-Earth
A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants, Uranus and Neptune, which are 14.5 and 17 times Earth's, respectively.
The term "super-Earth" refers only to ...
exoplanet
An exoplanet or extrasolar planet is a planet outside the Solar System. The first possible evidence of an exoplanet was noted in 1917 but was not recognized as such. The first confirmation of detection occurred in 1992. A different planet, init ...
orbiting
OGLE-2005-BLG-390L
OGLE-2005-BLG-390L is a star thought to be a spectral type M (a red dwarf; 95% probability, 4% probability it is a white dwarf, <1% probability it is a
Earth
Earth is the third planet from the Sun and the only astronomical object known to harbor life. While large volumes of water can be found throughout the Solar System, only Earth sustains liquid surface water. About 71% of Earth's sur ...
near the center of the
Milky Way
The Milky Way is the galaxy that includes our Solar System, with the name describing the galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars that cannot be individually distinguished by the naked eye. ...
Robotic Telescope Network
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 (Canary Islands), the Faulkes Telescope North on Maui (Hawaii), and the Faulke ...
(PLANET/Robonet),
Optical Gravitational Lensing Experiment
The Optical Gravitational Lensing Experiment (OGLE) is a Polish astronomical project based at the University of Warsaw that runs a long-term variability sky survey (1992–present). The main goals are the detection and classification of variable ...
(OGLE), and
Microlensing Observations in Astrophysics
Microlensing Observations in Astrophysics (MOA) 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 ...
The planet is estimated to be about five times Earth's mass (5.5 ). Some astronomers have speculated that it may have a rocky core like Earth, with a thin
atmosphere
An atmosphere () is a layer of gas or layers of gases that envelop a planet, and is held in place by the gravity of the planetary body. A planet retains an atmosphere when the gravity is great and the temperature of the atmosphere is low. A ...
. Its distance from the star, and the star's relatively low temperature, means that the planet's likely surface temperature is around , making it one of the coldest known. If it is a rocky world, this temperature would make it likely that the surface would be made of frozen
volatiles
Volatiles are the group of chemical elements and chemical compounds that can be readily vaporized. In contrast with volatiles, elements and compounds that are not readily vaporized are known as refractory substances.
On planet Earth, the term ...
, substances which would be liquids or gases on Earth: water,
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous ...
,
methane
Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane ...
and
nitrogen
Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...
would all be frozen solid. If it is ''not'' a rocky planet, it would more closely resemble an icy gas planet like
Uranus
Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus ( Caelus), who, according to Greek mythology, was the great-grandfather of Ares (Mars), grandfather of Zeus (Jupiter) and father of ...
, although much smaller.
The planet is notable for its large distance from its star for such a relatively small exoplanet - these planets are challenging to find with other detection methods. Prior to this, "small" exoplanets such as
Gliese 876 d
Gliese 876 d is an exoplanet approximately 15 light-years away in the constellation of Aquarius. The planet was the third planet discovered orbiting the red dwarf Gliese 876. It was the lowest-mass extrasolar planet apart from the pulsar planet ...
, which has an orbital period of less than 2 Earth-days, were detected very close to their stars. OGLE-2005-BLG-390Lb shows a combination of size and orbit that would not make it out of place in the
Solar System
The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...
.
"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
The National Science Foundation (NSF) is an independent agency of the United States government that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National ...
, which supported the work. At the time of discovery, with 5.5 Earth masses, the planet was less massive than the previous candidate for lowest-mass exoplanet around a main-sequence star, the 7.5 Earth mass Gliese 876 d. Since 2013, many Earth-sized or smaller planets around main-sequence stars have been detected by the ''Kepler'' spacecraft and others.
Host star
OGLE-2005-BLG-390L (located in the constellation Scorpius, RA 17:54:19.2, Dec −30°22′38″,
J2000
In astronomy, an epoch or reference epoch is a moment in time used as a reference point for some time-varying astronomical quantity. It is useful for the celestial coordinates or orbital elements of a celestial body, as they are subject to per ...
, 6.6 ± 1.0 kpc distance) is thought to likely be a cool
red dwarf
''Red Dwarf'' is a British science fiction comedy franchise created by Rob Grant and Doug Naylor, which primarily consists of a television sitcom that aired on BBC Two between 1988 and 1999, and on Dave since 2009, gaining a cult following. ...
(95% probability), or a
white dwarf
A white dwarf is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: its mass is comparable to the Sun's, while its volume is comparable to the Earth's. A white dwarf's faint luminosity comes ...
(4% probability), with a ''very'' slight chance that it is a
neutron star
A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich. Except for black holes and some hypothetical objects (e.g. w ...
or
black hole
A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape it. The theory of general relativity predicts that a sufficiently compact mass can def ...
(<1% probability). Regardless of the star's classification, its
radiant energy
Radiant may refer to:
Computers, software, and video games
* Radiant (software), a content management system
* GtkRadiant, a level editor created by id Software for their games
* Radiant AI, a technology developed by Bethesda Softworks for ''Th ...
output would be significantly less than that of the Sun. It has a mass of 0.22 , but an unknown radius. If it is a red dwarf, it would likely have a radius of 0.17 . The age is estimated to be around 9.587 billion years old.
Orbit
OGLE-2005-BLG-390Lb
orbit
In celestial mechanics, an orbit is the curved trajectory of an object such as the trajectory of a planet around a star, or of a natural satellite around a planet, or of an artificial satellite around an object or position in space such as ...
s its star every 3,500 days (about 10 years) at an average distance of , or an orbit that would fall between the orbits of
Mars
Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...
and
Jupiter
Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...
in the Solar System (This range of distances is the range of error in measurement and calculation; it does not represent the planet's
orbital eccentricity
In astrodynamics, the orbital eccentricity of an astronomical object is a dimensionless parameter that determines the amount by which its orbit around another body deviates from a perfect circle. A value of 0 is a circular orbit, values bet ...
, as its orbital elements are not known, other than its orbital period). Until this discovery, no small exoplanet had been found farther than from a
main-sequence
In astronomy, 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 ...
star. The planet takes approximately 10 Earth years to orbit its star,
OGLE-2005-BLG-390L
OGLE-2005-BLG-390L is a star thought to be a spectral type M (a red dwarf; 95% probability, 4% probability it is a white dwarf, <1% probability it is a
Discovery
OGLE-2005-BLG-390Lb's signature was first detected on January 25, 2006, by observations at the Danish 1.54-m telescope at ESO
La Silla Observatory
La Silla Observatory is an astronomical observatory in Chile with three telescopes built and operated by the European Southern Observatory (ESO). Several other telescopes are located at the site and are partly maintained by ESO. The observatory is ...
in
Chile
Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...
. The telescope was part of a network of telescopes used by the
PLANET
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
/
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 (Canary Islands), the Faulkes Telescope North on Maui (Hawaii), and the Faulke ...
gravitational microlensing
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers ...
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
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers ...
'' 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
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
/
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 (Canary Islands), the Faulkes Telescope North on Maui (Hawaii), and the Faulke ...
campaign regularly investigates promising
microlensing
Gravitational microlensing is an astronomical phenomenon due to the gravitational lens effect. It can be used to detect objects that range from the mass of a planet to the mass of a star, regardless of the light they emit. Typically, astronomers ...
event alerts that are issued by the PolishOGLE 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
OGLE-2005-BLG-390L is a star thought to be a spectral type M (a red dwarf; 95% probability, 4% probability it is a white dwarf, <1% probability it is a
PLANET
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
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
A planet is a large, rounded astronomical body that is neither a star nor its remnant. The best available theory of planet formation is the nebular hypothesis, which posits that an interstellar cloud collapses out of a nebula to create a you ...
,
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 (Canary Islands), the Faulkes Telescope North on Maui (Hawaii), and the Faulke ...
The planet has been given the unofficial name of Hoth by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agency of the US federal government responsible for the civil space program, aeronautics research, and space research.
NASA was established in 1958, succeedin ...
Star Wars
''Star Wars'' is an American epic space opera multimedia franchise created by George Lucas, which began with the eponymous 1977 film and quickly became a worldwide pop-culture phenomenon. The franchise has been expanded into various film ...
'' franchise. A similar exoplanet,
OGLE-2016-BLG-1195Lb
OGLE-2016-BLG-1195Lb is an extrasolar planet located about 22,000 light-years from Earth, in the galactic bulge, orbiting the 0.57 star OGLE-2016-BLG-1195L, discovered in 2017. The planet was detected using gravitational microlensing techniques ...
Gliese 581 g
Gliese 581g , unofficially known as Zarmina (or Zarmina's World), was a candidate exoplanet postulated to orbit within the Gliese 581 system, twenty light-years from Earth. It was discovered by the Lick–Carnegie Exoplanet Survey, and was the six ...
OGLE-2016-BLG-1195Lb
OGLE-2016-BLG-1195Lb is an extrasolar planet located about 22,000 light-years from Earth, in the galactic bulge, orbiting the 0.57 star OGLE-2016-BLG-1195L, discovered in 2017. The planet was detected using gravitational microlensing techniques ...
*
Optical Gravitational Lensing Experiment
The Optical Gravitational Lensing Experiment (OGLE) is a Polish astronomical project based at the University of Warsaw that runs a long-term variability sky survey (1992–present). The main goals are the detection and classification of variable ...