Eccentric Jupiter

Last updated
A computer simulation of the weather systems on the exoplanet HD 80606 b, an eccentric Jupiter. HD 80606 b's weather is extremely violent due to its highly eccentric orbit Exoplanet Comparison HD 80606 b.gif
A computer simulation of the weather systems on the exoplanet HD 80606 b, an eccentric Jupiter. HD 80606 b's weather is extremely violent due to its highly eccentric orbit

An eccentric Jupiter is a Jovian planet that orbits its star in an eccentric orbit. [1] Eccentric Jupiters may disqualify a planetary system from having Earth-like planets (though not always from having habitable exomoons) in it, because a massive gas giant with an eccentric orbit may eject all Earth mass exoplanets from the habitable zone, if not from the system entirely.

Contents

The planets of the solar system, except for Mercury, have orbits with an eccentricity of less than 0.1. However, two-thirds of the exoplanets discovered in 2006 have elliptical orbits with an eccentricity of 0.2 or more. [2] The typical exoplanet with an orbital period greater than five days has a median eccentricity of 0.23. [3] The discovery of this type of exoplanet, together with hot Jupiters, has challenged some widely-held theories about solar system formation.

History of discovery

The first exoplanet categorized as an eccentric Jupiter was confirmed in 1996, orbiting 16 Cygni. The first exoplanet around a main sequence star was discovered in 51 Pegasi the previous year. The celestial bodies that revolve around 16 Cygni and 70 Virginis with orbital eccentricities greater than 0.5 were initially regarded as brown dwarfs, prior to more accurate measurements of their masses.[ citation needed ]

Formation of eccentric orbits

Eccentric Jupiter HD 96167 b has a comet-like orbit. PlanetQuest-HD96167b.png
Eccentric Jupiter HD 96167 b has a comet-like orbit.

Various theories about the origin of orbits with high eccentricity compared to the planets of the solar system have been proposed, and can be modeled and analyzed via computer simulation. One model, termed the "slingshot model", describes such orbits in the case with a hot Jupiter in a multi-planetary system.

In any planetary system, the orbit of a planet is initially close to a perfect circle, but if there are three or more gas giant planets, its orbit will probably become distorted after a certain period of time. In some cases, one planet may be ejected from the system, and the remaining planets will fall into orbits with a very high eccentricity.

This is due to the fact that the energy exchanged between the three planets during their revolution is concentrated on a specific planet. This phenomenon almost always occurs after a certain period of time,[ quantify ] but when there are only one or two giant gas planets (that is, only Jupiter and Saturn in the solar system), the system is more stable over the lifespan of a main sequence star, and such a planet is virtually stable in a circular orbit. Therefore, there is a calculation result that each planet remains in a circular orbit semi-permanently in the solar system. Conversely, if there are three or more giant gas planets, the "fixed period" will be greatly affected by the mass and orbital spacing of the planets. If a massive planet has a narrow orbital spacing, this period will be shorter than the life of the star, and orbital crossing will occur shortly after the formation of the planetary system.

Another theory proposes that the interaction between giant planets and protoplanetary disks may increase eccentricity. [4] However, it is difficult to explain an eccentric planet with an eccentricity exceeding 0.4 with this mechanism. [5] Also, if the planet is orbiting a star belonging to a star system, the gravity of the companion star may increase the orbital eccentricity. [6]

Relation to hot Jupiters

It has been proposed that hot Jupiters, whose orbits have much smaller semi-major axes, evolve from gas giants in high-eccentricity orbits. For instance, an eccentric Jupiter may have an elongated elliptical orbit with periapsis around 0.05 au, and experience tidal braking upon its closest approach to its star. As a result, the planet settles into a roughly circular orbit with a semi-major axis comparable to its original periapsis, and thus receives a greater radiant flux throughout its entire orbit. For example, the eccentric planet HD 80606 b has an extremely elliptical orbit with a periapsis distance of 0.03 au and apoapsis distance of 0.87 au, and may be a celestial body that is transitioning to a hot Jupiter with an orbital radius of 0.03 au.

A limitation of this model is that that tidal forces weaken rapidly at greater orbital distances (inversely proportional to the cube of the distance), requiring a planet to orbit closer to the main star for a longer time period to experience sufficient braking. As an example, if another giant planet has a more distant orbit than the celestial body that is evolving into a hot Jupiter, its gravity will change the periapsis distance of the inner planet, and if the potentially evolving body has a stable orbit with a too-distant periapsis, the tidal force will be almost ineffective. In addition, hot Jupiters have been found at slightly more distant orbits – with semi-major axes of at least 0.1 au – but another model is needed to explain these.

Confusion with multiplanetary systems

Some of the detected "eccentric planets" may actually be multiple planets with near-circular orbits. [7] [8] The majority of eccentric planets have been reported based on radial velocity measurements using Doppler spectroscopy by which eccentricity is directly measurable. In the case where the planet is in a circular orbit, the fluctuation pattern of the radial velocity is a simple sine curve, but in the case of an elliptical orbit, it deviates from the sine curve and is recognized as an eccentric planet. However, such a distorted waveform can also occur due to the synthesis of radial velocity fluctuations (wave interference) caused by multiple planets. The two cannot be distinguished if the radial velocity sampling is insufficient (the number of times is small, only a part of the orbital period can be covered, etc.). In this situation, the simplest model that can reproduce the observations is preferred to be a single eccentric planet rather than a multiplanetary system.

Due to these circumstances, there are cases where observations initially attributed to an eccentric planet were instead due to a multiplanetary system with planets in low-eccentricity orbits, due to the accumulation of observations and improvements in analytical techniques. As an example, a study that re-examined 82 planetary systems that were alleged to have a single eccentric planet in 2013 found that multiplanetary models were more accurate than single-planet models; nine multiplanetary systems were reported. [9]

The situation where multiple planetary systems and eccentric planets are confused is likely to occur in cases where the waveform distortion is relatively small, such as when the eccentricity is 0.5 or less when interpreted as a single planet. On the other hand, a planet with an orbital eccentricity of 0.5 or more is considered unlikely to be mistaken for a multiplanetary system.

List

This is a list of eccentric Jupiters: [2]

Planet a (AU) e MJ Notes
54 Piscium b 0.290.610.22Might allow for planets at or beyond 0.6 AU
HD 37605 b 0.260.732.84Might allow for planets at or beyond 0.8 AU
HD 45350 b 1.920.771.79Restricted stable orbits to the innermost 0.2 AU
HD 80606 b 0.450.934.0Only beyond 1.75 AU did simulated particles remain
HD 20782 b 1.3810.972.620
HD 89744 b 0.930.678.58No terrestrial planets in the habitable zone
16 Cygni Bb 1.680.681.68No terrestrial planets in the habitable zone

See also

Related Research Articles

<span class="mw-page-title-main">Upsilon Andromedae</span> Star in the constellation Andromeda

Upsilon Andromedae is a binary star located 44 light-years from Earth in the constellation of Andromeda. The system consists of an F-type main-sequence star and a smaller red dwarf.

<span class="mw-page-title-main">Hot Jupiter</span> Class of high mass planets orbiting close to a star

Hot Jupiters are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter but that have very short orbital periods. The close proximity to their stars and high surface-atmosphere temperatures resulted in their informal name "hot Jupiters".

HD 74156 is a yellow dwarf star in the constellation of Hydra, 187 light years from the Solar System. It is known to be orbited by two giant planets.

<span class="mw-page-title-main">16 Cygni</span> Multiple star in the constellation Cygnus

16 Cygni or 16 Cyg is a triple star system approximately 69 light-years away from Earth in the constellation of Cygnus. It consists of two Sun-like yellow dwarf stars, 16 Cygni A and 16 Cygni B, together with a red dwarf, 16 Cygni C. In 1996 an extrasolar planet was discovered in an eccentric orbit around 16 Cygni B.

<span class="mw-page-title-main">54 Piscium</span> Orange dwarf star in the constellation Pisces

54 Piscium is an orange dwarf star approximately 36 light-years away in the constellation of Pisces. In 2003, an extrasolar planet was confirmed to be orbiting the star, and in 2006, a brown dwarf was also discovered orbiting it.

<span class="mw-page-title-main">16 Cygni Bb</span> Extrasolar planet

16 Cygni Bb or HD 186427 b is an extrasolar planet approximately 69 light-years away in the constellation of Cygnus. The planet was discovered orbiting the Sun-like star 16 Cygni B, one of two solar-mass (M☉) components of the triple star system 16 Cygni in 1996. It orbits its star once every 799 days and was the first eccentric Jupiter and planet in a double star system to be discovered. The planet is abundant in lithium.

Upsilon Andromedae d, formally named Majriti, is a super-Jupiter exoplanet orbiting within the habitable zone of the Sun-like star Upsilon Andromedae A, approximately 44 light-years away from Earth in the constellation of Andromeda. Its discovery made it the first multiplanetary system to be discovered around a main-sequence star, and the first such system known in a multiple star system. The exoplanet was found by using the radial velocity method, where periodic Doppler shifts of spectral lines of the host star suggest an orbiting object.

HD 147506, also known as HAT-P-2 and formally named Hunor, is a magnitude 8.7 F8 dwarf star that is somewhat larger and hotter than the Sun. The star is approximately 419 light-years from Earth and is positioned near the keystone of Hercules. It is estimated to be 2 to 3 billion years old, towards the end of its main sequence life. There is one known transiting exoplanet, and a second planet not observed to transit.

This page describes exoplanet orbital and physical parameters.

<span class="mw-page-title-main">WASP-8b</span> Planet orbiting a star in a binary system in the constellation of Sculptor

WASP-8b is an exoplanet orbiting the star WASP-8A in the constellation of Sculptor. The star is similar to the Sun and forms a binary star with a red dwarf star (WASP-8B) of half the Sun's mass that orbits WASP-8A 4.5 arcseconds away. The system is 294 light-years away and is therefore located closer to Earth than many other star systems that are known to feature planets similar to WASP-8b. The planet and its parent star were discovered in the SuperWASP batch -6b to -15b. On 1 April 2008, Dr. Don Pollacco of Queen's University Belfast announced them at the RAS National Astronomy Meeting.

<span class="mw-page-title-main">HD 80606 b</span> Eccentric hot Jupiter in the constellation Ursa Major

HD 80606 b is an eccentric hot Jupiter 217 light-years from the Sun in the constellation of Ursa Major. HD 80606 b was discovered orbiting the star HD 80606 in April 2001 by a team led by Michel Mayor and Didier Queloz. With a mass 4 times that of Jupiter, it is a gas giant. Because the planet transits the host star its radius can be determined using the transit method, and was found to be about the same as Jupiter's. Its density is slightly less than Earth's. It has an extremely eccentric orbit like a comet, with its orbit taking it very close to its star and then back out very far away from it every 111 days.

<span class="mw-page-title-main">HD 17156 b</span> Extrasolar planet in the constellation of Cassiopeia

HD 17156 b, named Mulchatna by the IAU, is an extrasolar planet approximately 255 light-years away in the constellation of Cassiopeia. The planet was discovered orbiting the yellow subgiant star HD 17156 in April 2007. The planet is classified as a relatively cool hot Jupiter planet slightly smaller than Jupiter but slightly larger than Saturn. This highly-eccentric three-week orbit takes it approximately 0.0523 AU of the star at periastron before swinging out to approximately 0.2665 AU at apastron. Its eccentricity is about the same as 16 Cygni Bb, a so-called "eccentric Jupiter". Until 2009, HD 17156 b was the transiting planet with the longest orbital period.

HD 240237 b is a super-Jupiter exoplanet orbiting the K-type giant star HD 240237 about 4,900 light-years (1,500 parsecs, or nearly 4.6×1016 km) away from Earth in the constellation Cassiopeia. It orbits outside of the habitable zone of its star at a distance of 1.9 AU. The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star. The planet has a mildly eccentric orbit.

HD 1690 is a giant star with an orbiting exoplanet companion in the constellation of Cetus. It has an apparent visual magnitude of 9.19, which is too faint to be visible to the naked eye. The distance to this system is approximately 2,570 light years, and it is drifting further away with a radial velocity of +18.2 km/s. HD 1690 has no known companion star, making it a single star system.

References

  1. ↑ Raymond, Sean N; Quinn, Thomas; Lunine, Jonathan I (March 2004). "Making other earths: dynamical simulations of terrestrial planet formation and water delivery". Icarus . 168 (1): 1–17. arXiv: astro-ph/0308159 . Bibcode:2004Icar..168....1R. doi:10.1016/j.icarus.2003.11.019. S2CID   9990348. Note: this study treats eccentric Jupiters as giant planets having an orbital eccentricity of 0.1 or greater.
  2. 1 2 Wittenmyer, Robert A.; Endl, Michael; Cochran, William D.; Levison, Harold F. (31 July 2007). "Dynamical and Observational Constraints on Additional Planets in Highly Eccentric Planetary Systems". The Astronomical Journal . 134 (3): 1276–1284. arXiv: 0706.1962 . Bibcode:2007AJ....134.1276W. doi:10.1086/520880. ISSN   0004-6256. S2CID   14345035.
  3. ↑ Peek, Kathryn M. G.; Johnson, John Asher; Fischer, Debra A.; Marcy, Geoffrey W.; Henry, Gregory W.; Howard, Andrew W.; Wright, Jason T.; Lowe, Thomas B.; Reffert, Sabine; Schwab, Christian; Williams, Peter K. G.; Isaacson, Howard; Giguere, Matthew J.; et al. (June 2009). "Old, Rich, and Eccentric: Two Jovian Planets Orbiting Evolved Metal-Rich Stars". Publications of the Astronomical Society of the Pacific . 121 (880): 613–620. arXiv: 0904.2786 . Bibcode:2009PASP..121..613P. doi:10.1086/599862. ISSN   0004-6280. S2CID   12042779.
  4. ↑ Goldreich, Peter; Sari, Re'em (10 March 2003). "Eccentricity Evolution for Planets in Gaseous Disks". The Astrophysical Journal . 585 (2): 1024–1037. arXiv: astro-ph/0202462 . Bibcode:2003ApJ...585.1024G. doi:10.1086/346202. ISSN   0004-637X. S2CID   21141134.
  5. ↑ Sari, Re'em; Goldreich, Peter (May 2004). "Planet-Disk Symbiosis". The Astrophysical Journal . 606 (1): L77–L80. arXiv: astro-ph/0307107 . Bibcode:2004ApJ...606L..77S. doi:10.1086/421080. ISSN   0004-637X. S2CID   13388108.
  6. ↑ Holman, Matthew; Touma, Jihad; Tremaine, Scott (March 1997). "Chaotic variations in the eccentricity of the planet orbiting 16 Cygni B". Nature . 386 (6622): 254–256. Bibcode:1997Natur.386..254H. doi:10.1038/386254a0. ISSN   0028-0836. S2CID   4312547.
  7. ↑ Wittenmyer, Robert A; Clark, Jake T; Zhao, Jinglin; Horner, Jonathan; Wang, Songhu; Johns, Daniel (21 April 2019). "Truly eccentric – I. Revisiting eight single-eccentric planetary systems". Monthly Notices of the Royal Astronomical Society . 484 (4): 5859–5867. arXiv: 1901.08471 . doi: 10.1093/mnras/stz290 . ISSN   0035-8711.
  8. ↑ Anglada-Escudé, Guillem; López-Morales, Mercedes; Chambers, John E. (29 December 2009). "How eccentric orbital solutions can hide planetary systems in 2:1 resonant orbits". The Astrophysical Journal . 709 (1): 168–178. arXiv: 0809.1275 . doi: 10.1088/0004-637X/709/1/168 . ISSN   0004-637X. S2CID   2756148.
  9. ↑ Wittenmyer, Robert A.; Wang, Songhu; Horner, Jonathan; Tinney, C. G.; Butler, R. P.; Jones, H. R. A.; O'Toole, S. J.; Bailey, J.; Carter, B. D.; Salter, G. S.; Wright, D.; Zhou, Ji-Lin (22 August 2013). "Forever alone? Testing single eccentric planetary systems for multiple companions". The Astrophysical Journal Supplement Series . 208 (1): 2. arXiv: 1307.0894 . Bibcode:2013ApJS..208....2W. doi:10.1088/0067-0049/208/1/2. ISSN   0067-0049. S2CID   14109907.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.