Hypothetical fifth gas giant
Encyclopedia
The fifth gas giant hypothesis is an attempt to explain apparent inconsistencies in the formation of the Solar System
. Apart from Jupiter
, Saturn
, Uranus
and Neptune
, theorists argue that there was once a fifth gas giant, which was expelled from the Solar System in its formative period.
and Neptune
in their present positions; it is contended that the gaseous primordial disc of dust and gas that formed the early Solar System would have been too diffuse and unable to account for the bulk of these ice giant
planets. It is therefore theorized that the early Solar System was more compact than at present, and that they migrated to their current positions as free interstellar gas and dust involved in their formation was incorporated into them.
in Boulder
, Colorado
, there was originally a third ice giant between the orbits of Saturn and Uranus that was expelled from the Solar System after a close encounter with Jupiter
slung it into interstellar space. The hypothesis is explored in Nesvorney's paper for Astrophysical Journal Letters.
In 2007, Eric B. Ford (Harvard-Smithsonian Center for Astrophysics
) and Eustace Chiang (Center for Integrative Planetary Science) University of California, Berkeley
) presented a similar paper within the journal, arguing for the presence of such a hypothetical object as an explanatory mechanism for prior difficulties in existing theories of planetary formation.
There may have been more than one ice giant involved in the process described above, although Nesvorny's reconstruction of a fifth ice giant presence seems to offer the best prospects for the ultimate emergence of a Solar System configured much like our own.
s of the Solar System—Mercury
, Venus
, Earth
and Mars
—as well as possible additional protoplanets that were lost in the early period of planetary formation due to collisions or accretion with other bodies. In this framework, Jupiter lost angular momentum
when it flung the fifth gas giant out of the Solar System, leading Jupiter to recede from the Sun's vicinity, insuring the stability and survival of the inner planets and causing turbulence within the Kuiper belt
and Oort cloud
en-route out of the Solar System. This may have led to intensive and numerous cometary and asteroid impacts in the inner Solar System, resulting in intensive cratering. This period is known as the Late Heavy Bombardment
and occurred 3.9 billion years ago.
The whereabouts of the hypothetical fifth gas giant are currently unknown, although according to Takahiro Sumi of Osaka University
, other observable rogue planets exist in interstellar space away from other stars.
, after the Greek god of the underworld: Liber
, the Roman god of wine and a cognate of Dionysus
and Bacchus
: and Mephitis
, the Roman goddess of toxic gases. Another suggestion is "Thing 1" from Dr. Seuss' Cat in the Hat children's book.
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...
. Apart from 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,...
, Saturn
Saturn
Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn is named after the Roman god Saturn, equated to the Greek Cronus , the Babylonian Ninurta and the Hindu Shani. Saturn's astronomical symbol represents the Roman god's sickle.Saturn,...
, 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...
and 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...
, theorists argue that there was once a fifth gas giant, which was expelled from the Solar System in its formative period.
Background
Current theories of planetary formation do not allow for the coalescence and development of UranusUranus
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...
and 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...
in their present positions; it is contended that the gaseous primordial disc of dust and gas that formed the early Solar System would have been too diffuse and unable to account for the bulk of these ice giant
Ice giant
Ice Giant or Ice giants may refer to:* A type of gas giant composed largely of materials less volatile than hydrogen and helium* The frost giants of Norse mythology, see also Hrimthurs...
planets. It is therefore theorized that the early Solar System was more compact than at present, and that they migrated to their current positions as free interstellar gas and dust involved in their formation was incorporated into them.
Hypothetical additional trans-Saturnian ice giant
However, computer simulations indicate that the process of migration should have displaced either Uranus or Neptune. According to David Nesvorny of the Southwest Research InstituteSouthwest Research Institute
Southwest Research Institute , headquartered in San Antonio, Texas, is one of the oldest and largest independent, nonprofit, applied research and development organizations in the United States...
in Boulder
Boulder
In geology, a boulder is a rock with grain size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....
, Colorado
Colorado
Colorado is a U.S. state that encompasses much of the Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains...
, there was originally a third ice giant between the orbits of Saturn and Uranus that was expelled from the Solar System after a close encounter with 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,...
slung it into interstellar space. The hypothesis is explored in Nesvorney's paper for Astrophysical Journal Letters.
In 2007, Eric B. Ford (Harvard-Smithsonian Center for Astrophysics
Harvard-Smithsonian Center for Astrophysics
The Harvard–Smithsonian Center for Astrophysics is one of the largest and most diverse astrophysical institutions in the world, where scientists carry out a broad program of research in astronomy, astrophysics, earth and space sciences, and science education...
) and Eustace Chiang (Center for Integrative Planetary Science) University of California, Berkeley
University of California, Berkeley
The University of California, Berkeley , is a teaching and research university established in 1868 and located in Berkeley, California, USA...
) presented a similar paper within the journal, arguing for the presence of such a hypothetical object as an explanatory mechanism for prior difficulties in existing theories of planetary formation.
There may have been more than one ice giant involved in the process described above, although Nesvorny's reconstruction of a fifth ice giant presence seems to offer the best prospects for the ultimate emergence of a Solar System configured much like our own.
Fifth gas giant and formation of terrestrial planets
Nesvorny argues that his hypothesis also accounts for the survival of the inner terrestrial planetTerrestrial planet
A terrestrial planet, telluric planet or rocky planet is a planet that is composed primarily of silicate rocks or metals. Within the Solar System, the terrestrial planets are the inner planets closest to the Sun...
s of the Solar System—Mercury
Mercury (planet)
Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 87.969 Earth days. The orbit of Mercury has the highest eccentricity of all the Solar System planets, and it has the smallest axial tilt. It completes three rotations about its axis for every two orbits...
, Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
, Earth
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...
and 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...
—as well as possible additional protoplanets that were lost in the early period of planetary formation due to collisions or accretion with other bodies. In this framework, Jupiter lost angular momentum
Angular momentum
In physics, angular momentum, moment of momentum, or rotational momentum is a conserved vector quantity that can be used to describe the overall state of a physical system...
when it flung the fifth gas giant out of the Solar System, leading Jupiter to recede from the Sun's vicinity, insuring the stability and survival of the inner planets and causing turbulence within the Kuiper belt
Kuiper belt
The Kuiper belt , sometimes called the Edgeworth–Kuiper belt, is a region of the Solar System beyond the planets extending from the orbit of Neptune to approximately 50 AU from the Sun. It is similar to the asteroid belt, although it is far larger—20 times as wide and 20 to 200 times as massive...
and Oort cloud
Oort cloud
The Oort cloud , or the Öpik–Oort cloud , is a hypothesized spherical cloud of comets which may lie roughly 50,000 AU, or nearly a light-year, from the Sun. This places the cloud at nearly a quarter of the distance to Proxima Centauri, the nearest star to the Sun...
en-route out of the Solar System. This may have led to intensive and numerous cometary and asteroid impacts in the inner Solar System, resulting in intensive cratering. This period is known as the Late Heavy Bombardment
Late Heavy Bombardment
The Late Heavy Bombardment is a period of time approximately 4.1 to 3.8 billion years ago during which a large number of impact craters are believed to have formed on the Moon, and by inference on Earth, Mercury, Venus, and Mars as well...
and occurred 3.9 billion years ago.
The whereabouts of the hypothetical fifth gas giant are currently unknown, although according to Takahiro Sumi of Osaka University
Osaka University
, or , is a major national university located in Osaka, Japan. It is the sixth oldest university in Japan as the Osaka Prefectural Medical College, and formerly one of the Imperial Universities of Japan...
, other observable rogue planets exist in interstellar space away from other stars.
Mooted names
According to Nesvorny, colleagues have suggested several names for the hypothetical fifth ice giant- HadesHades
Hades , Hadēs, originally , Haidēs or , Aidēs , meaning "the unseen") was the ancient Greek god of the underworld. The genitive , Haidou, was an elision to denote locality: "[the house/dominion] of Hades". Eventually, the nominative came to designate the abode of the dead.In Greek mythology, Hades...
, after the Greek god of the underworld: Liber
Liber
In ancient Roman religion and mythology, Liber , also known as Liber Pater was a god of viticulture and wine, fertility and freedom. He was a patron deity of Rome's plebeians and was part of their Aventine Triad. His festival of Liberalia became associated with free speech and the rights...
, the Roman god of wine and a cognate of Dionysus
Dionysus
Dionysus was the god of the grape harvest, winemaking and wine, of ritual madness and ecstasy in Greek mythology. His name in Linear B tablets shows he was worshipped from c. 1500—1100 BC by Mycenean Greeks: other traces of Dionysian-type cult have been found in ancient Minoan Crete...
and Bacchus
Bacchus
Bacchus is the Roman name for Dionysus, the god of wine and intoxication.Bacchus can also refer to:* Temple of Bacchus, a Roman temple at a large classical antiquity complex in Baalbek, Lebanon...
: and Mephitis
Mephitis
Mephitis may refer to:* Mephitis , one of the three genera of skunks* An alternate spelling for the Roman goddess Mefitis...
, the Roman goddess of toxic gases. Another suggestion is "Thing 1" from Dr. Seuss' Cat in the Hat children's book.