Tyche (hypothetical Planet)
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Tyche is a hypothetical
gas giant A gas giant is a giant planet composed mainly of hydrogen and helium. Jupiter and Saturn are the gas giants of the Solar System. The term "gas giant" was originally synonymous with "giant planet". However, in the 1990s, it became known that Uranu ...
located in the
Solar System The Solar SystemCapitalization 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 "Sola ...
's
Oort cloud The Oort cloud (pronounced or ), sometimes called the Öpik–Oort cloud, is scientific theory, theorized to be a cloud of billions of Volatile (astrogeology), icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 A ...
, first proposed in 1999 by astrophysicists John Matese, Patrick Whitman and Daniel Whitmire of the
University of Louisiana at Lafayette The University of Louisiana at Lafayette (UL Lafayette, University of Louisiana, ULL, or UL) is a Public university, public research university in Lafayette, Louisiana, United States. It has the largest enrollment within the nine-campus Universi ...
. They argued that evidence of Tyche's existence could be seen in a supposed bias in the points of origin for
long-period comet A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or coma surrounding the nucleus, and ...
s. More recently, Matese and Whitmire re-evaluated the comet data and noted that Tyche, if it existed, would be detectable in the archive of data that was collected by
NASA The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
's
Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...
(WISE) telescope. In 2014, NASA announced that the WISE survey had ruled out any object with Tyche's characteristics, indicating that Tyche as hypothesized by Matese, Whitman, and Whitmire does not exist.


History

Matese, Whitmire and their colleague Patrick Whitman first proposed the existence of this planet in 1999, based on observations of the orbits of long-period comets. Most astronomers agree that long-period comets (those with orbits of thousands to millions of years) have a roughly isotropic distribution; that is, they arrive at random from every point in the sky. Because comets are volatile and dissipate over time, astronomers suspect that they must be held in a spherical cloud tens of thousands of AU distant (known as the
Oort cloud The Oort cloud (pronounced or ), sometimes called the Öpik–Oort cloud, is scientific theory, theorized to be a cloud of billions of Volatile (astrogeology), icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 A ...
) for most of their existence. However, Matese and Whitmire claimed that rather than arriving from random points across the sky as is commonly thought, comet orbits were in fact clustered in a band inclined to the orbital plane of the planets. Such clustering could be explained if they were disturbed by an unseen object at least as large as
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
, possibly a
brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...
, located in the outer part of the
Oort cloud The Oort cloud (pronounced or ), sometimes called the Öpik–Oort cloud, is scientific theory, theorized to be a cloud of billions of Volatile (astrogeology), icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 A ...
. They also suggested that such an object might explain the
trans-Neptunian object A trans-Neptunian object (TNO), also written transneptunian object, is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, which has an orbital semi-major axis of 30.1 astronomical units (AU). ...
Sedna's peculiar orbit. However, the sample size of Oort comets was small and the results were inconclusive.


Orbit

Whitmire and Matese speculated that Tyche's orbit would lie at approximately 500 times
Neptune Neptune is the eighth and farthest known planet from the Sun. It is the List of Solar System objects by size, fourth-largest planet in the Solar System by diameter, the third-most-massive planet, and the densest giant planet. It is 17 t ...
's distance, some from the
Sun The Sun is the star at the centre of the Solar System. It is a massive, nearly perfect sphere of hot plasma, heated to incandescence by nuclear fusion reactions in its core, radiating the energy from its surface mainly as visible light a ...
, a little less than one quarter of a
light year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distance, astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by t ...
. This is well within the
Oort cloud The Oort cloud (pronounced or ), sometimes called the Öpik–Oort cloud, is scientific theory, theorized to be a cloud of billions of Volatile (astrogeology), icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 A ...
, whose boundary is estimated to be beyond 50,000 AU. It would have an orbital period of roughly 1.8 million years. A failed search of older
IRAS The Infrared Astronomical Satellite (Dutch language, Dutch: ''Infrarood Astronomische Satelliet'') (IRAS) was the first space telescope to perform a astronomical survey, survey of the entire night sky at infrared wavelengths. Launched on 25 Janu ...
data suggests that an object of would need to have a distance greater than 10,000 AU. Such a planet would orbit in a plane different from the ecliptic, and would probably have been in a wide-binary orbit at the time of its formation. Wide binaries may form through capture during the dissolution of a star's birth cluster.


Mass

In 2011, Whitmire and Matese speculated that the hypothesized planet could be up to four times the mass of
Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...
and have a relatively high temperature of approximately , due to residual heat from its formation and Kelvin–Helmholtz heating. It would be insufficiently massive to undergo
nuclear fusion Nuclear fusion is a nuclear reaction, reaction in which two or more atomic nuclei combine to form a larger nuclei, nuclei/neutrons, neutron by-products. The difference in mass between the reactants and products is manifested as either the rele ...
reactions in its interior, a process that occurs in objects above roughly 13 Jupiter masses. Although more massive than Jupiter, Tyche would be about Jupiter's size since degenerate pressure causes massive gas giants to increase only in density, not in size, relative to their mass. If Tyche was to be found, it was expected to be found by the end of 2013 and only be 1–2 Jupiter masses.


Origin of name

Tyche Tyche (; Ancient Greek: Τύχη ''Túkhē'', 'Luck', , ; Roman mythology, Roman equivalent: Fortuna) was the presiding tutelary deity who governed the fortune and prosperity of a city, its destiny. In Classical Greek mythology, she is the dau ...
(, meaning "fortune" or "luck" in
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
) was the
Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...
goddess of fortune and prosperity. The name was chosen to avoid confusion with an earlier similar hypothesis that the Sun has a dim companion named ''
Nemesis In ancient Greek religion and myth, Nemesis (; ) also called Rhamnousia (or Rhamnusia; ), was the goddess who personified retribution for the sin of hubris: arrogance before the gods. Etymology The name ''Nemesis'' is derived from the Greek ...
'', whose gravity triggers influxes of comets into the inner Solar System, leading to mass-extinctions on
Earth Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
.
Tyche Tyche (; Ancient Greek: Τύχη ''Túkhē'', 'Luck', , ; Roman mythology, Roman equivalent: Fortuna) was the presiding tutelary deity who governed the fortune and prosperity of a city, its destiny. In Classical Greek mythology, she is the dau ...
was the name of the "good sister" of
Nemesis In ancient Greek religion and myth, Nemesis (; ) also called Rhamnousia (or Rhamnusia; ), was the goddess who personified retribution for the sin of hubris: arrogance before the gods. Etymology The name ''Nemesis'' is derived from the Greek ...
. This name was first used for an outer Oort cloud object by J. Davy Kirkpatrick at the Infrared Processing and Analysis Center of the California Institute of Technology.


WISE mission

The
Wide-field Infrared Survey Explorer Wide-field Infrared Survey Explorer (WISE, List of observatory codes, observatory code C51, Explorer 92 and MIDEX-6) was a NASA infrared astronomy Space observatory, space telescope in the Explorers Program launched in December 2009.. . WISE L ...
(WISE)
space telescope A space telescope (also known as space observatory) is a telescope in outer space used to observe astronomical objects. Suggested by Lyman Spitzer in 1946, the first operational telescopes were the American Orbiting Astronomical Observatory, OAO ...
has completed an all-sky infrared survey that includes areas where Whitmire and Matese anticipate that Tyche may be found. On March 14, 2012, the first-pass all-sky survey catalog of the WISE mission was released. The co-added (AllWISE) post-cryo second survey of the sky was released at the end of 2013.Wide-field Infrared Survey Explorer
/ref> On March 7, 2014, NASA reported that the WISE telescope had ruled out the possibility of a Saturn-sized object out to 10,000—28,000 AU, and a Jupiter-sized or larger object out to 26,000—82,000 AU (0.4
light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...
s).


See also

* Kelvin–Helmholtz heating *
Nemesis (hypothetical star) Nemesis is a hypothetical astronomical objects, hypothetical red dwarf or brown dwarf, originally postulated in 1984 to be orbiting the Sun at a distance of about 95,000 astronomical unit, AU (1.5 light-years), somewhat beyond the Oort cloud, to e ...
*
Planet Nine Planet Nine is a List of hypothetical Solar System objects, hypothetical ninth planet in the outer region of the Solar System. Its gravitational effects could explain the peculiar clustering of orbits for a group of extreme trans-Neptunian obj ...
*
Planets beyond Neptune Following the discovery of the planet Neptune in 1846, there was considerable speculation that another planet might exist beyond its orbit. The search began in the mid-19th century and continued at the start of the 20th with Percival Lowell's ...
*
Vulcan (hypothetical planet) Vulcan () was a proposed planet that some pre-20th century astronomers thought existed in an orbit between Mercury (planet), Mercury and the Sun. Speculation about, and even purported observations of, intermercurial bodies or planets date back t ...


Notes


References

{{Portal bar, Stars, Spaceflight, Outer space, Science Hypothetical bodies of the Solar System Solar System dynamic theories Hypothetical planets Hypothetical trans-Neptunian objects Oort cloud Astronomical controversies Solar System Hypothetical astronomical objects