OGLE-2005-BLG-390Lb (known sometimes as

Hoth Hoth is an ice planet in the ''Star Wars'' fictional universe. It first appeared in the 1980 film ''The Empire Strikes Back'' and has also been a setting in ''Star Wars'' books and video games. Description Hoth is the sixth planet of a remote s ...

by NASA) 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, a star from

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 surfa ...

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 ...

, making it one of the most distant planets known. On January 25, 2006, Probing Lensing Anomalies NETwork/ Robotic Telescope Network (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, a ...

(MOA) made a joint announcement of the discovery. The planet does not appear to meet conditions presumed necessary to support life.

Characteristics

Mass, radius and temperature

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 s ...

. 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 w ...

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 on ...

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 sevent ...

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 plane ...

, 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 Scorpius is a zodiac constellation located in the Southern celestial hemisphere, where it sits near the center of the Milky Way, between Libra to the west and Sagittarius to the east. Scorpius is an ancient constellation that pre-dates the G ...

, 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 (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 f ...

(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 ...

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 defo ...

(<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 '' ...

output would be significantly less than that of the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

. 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 a ...

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 atm ...

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-thousandth t ...

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 Hert ...

star. The planet takes approximately 10 Earth years to orbit its star, OGLE-2005-BLG-390L.

Discovery

OGLE-2005-BLG-390Lb's signature was first detected on January 25, 2006, by observations at the

Danish Danish may refer to: * Something of, from, or related to the country of Denmark People * A national or citizen of Denmark, also called a "Dane," see Demographics of Denmark * Culture of Denmark * Danish people or Danes, people with a Danish ance ...

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 i ...

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 east a ...

. 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 yo ...

/ RoboNet

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 The Perth Observatory is the name of two astronomical observatories located in Western Australia (WA). In 1896, the original observatory was founded in West Perth on Mount Eliza overlooking the city of Perth (obs. code 319). Due to the city ...

in Western Australia.

Gravitational lensing A gravitational lens is a distribution of matter (such as a cluster of galaxies) between a distant light source and an observer that is capable of bending the light from the source as the light travels toward the observer. This effect is known ...

occurs when light from a distant star is bent and magnified by the gravitational field of a foreground star. A ''

'' 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

/ RoboNet campaign regularly investigates promising microlensing event alerts that are issued by the

Polish Polish may refer to: * Anything from or related to Poland, a country in Europe * Polish language * Poles, people from Poland or of Polish descent * Polish chicken *Polish brothers (Mark Polish and Michael Polish, born 1970), American twin scree ...

OGLE Ogle may refer to: Places * Ogle County, Illinois, United States * Original name of Ashton, Illinois, a village * Ogle, Kentucky, United States, an unincorporated community * Ogle Township, Somerset County, Pennsylvania, United States * Ogle, ...

or the Japanese–New Zealand

MOA Moa are extinct giant flightless birds native to New Zealand. The term has also come to be used for chicken in many Polynesian cultures and is found in the names of many chicken recipes, such as Kale moa and Moa Samoa. Moa or MOA may also refer ...

survey. The observation of just such an event led to the discovery of OGLE-2005-BLG-390Lb.

detected the microlensing effect produced by the star OGLE-2005-BLG-390L, and it was the

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

, RoboNet,

, and

In popular culture

The planet has been given the unofficial name of Hoth by NASA due to its resemblance to the planet with the same name from the '' Star Wars'' franchise. A similar exoplanet, OGLE-2016-BLG-1195Lb, has also been compared to Hoth.

References

External links

Informative

MOA collaborationOGLE collaboration

Planet Homepage

News

* *

Videos

* {{DEFAULTSORT:Ogle-2005-Blg-390lb Super-Earths Scorpius (constellation) Terrestrial planets Exoplanets discovered in 2005 Exoplanets detected by microlensing