Brown-dwarf desert

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The brown dwarf OGLE-2015-BLG-1319, discovered in 2016, possibly does fall in the desert range. PIA21076 Brown Dwarf Microlensing (Illustration), Figure 1.jpg
The brown dwarf OGLE-2015-BLG-1319, discovered in 2016, possibly does fall in the desert range.

The brown-dwarf desert is a theorized range of orbits around a star within which brown dwarfs are unlikely to be found as companion objects. [1] This is usually up to 5 AU around solar mass stars. The paucity of brown dwarfs in close orbits was first noted between 1998 and 2000 when a sufficient number of extrasolar planets had been found to perform statistical studies. Astronomers discovered there is a distinct shortage of brown dwarfs within 5 AU of the stars with companions, while there was an abundance of free-floating brown dwarfs being discovered. [2] Subsequent studies have shown that brown dwarfs orbiting within 3–5 AU are found around less than 1% of stars with a mass similar to the Sun (M☉). [3] [4] Of the brown dwarfs that were found in the brown-dwarf desert, most were found in multiple systems, suggesting that binarity was a key factor in the creation of brown-dwarf desert inhabitants. [5]

One of the many possible reasons for the existence of the desert relates to planetary (and brown dwarf) migration. If a brown dwarf were to form within 5 AU of its companion star, it could plausibly begin migrating inwards towards the central star and eventually fall into the star itself.[ citation needed ] That being said, the exact details of migration within a protoplanetary disk are not completely understood, and it is equally plausible that brown dwarf companions to FGK dwarfs would not undergo appreciable migration after their formation. A second possible reason is, depending on which formation paradigm is invoked, that a formation by core accretion should make the formation of higher mass brown dwarfs unlikely, as the gas accretion rate during runaway accretion onto high mass forming objects is reduced due to gap formation in the disk. The limited disk life time then truncates the mass range, limiting the maximum masses to approximately 10 Jupiter masses (MJ). [6] This effect might be somewhat mitigated by the fact that objects of 3–5 MJ and above might excite eccentric perturbations in the disk, allowing for non-negligible mass accretion even in the presence of a gap. [7] Objects that form further outside (a>80 AU), where the disk is prone to gravitational instabilities, might be able to reach the masses required to cross the planet–brown dwarf threshold. [8] For these objects it might be unlikely to migrate into the inner regions of the disk, however, due to the long type-II migration timescale for massive objects in the brown dwarf mass regime. [9]

See also

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<span class="mw-page-title-main">Brown dwarf</span> Type of substellar object larger than a planet

Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars. Their mass is approximately 13 to 80 times that of Jupiter (MJ) -- not big enough to sustain nuclear fusion of ordinary hydrogen (1H) into helium in their cores, but massive enough to emit some light and heat from the fusion of deuterium (2H). The most massive ones can fuse lithium (7Li).

<span class="mw-page-title-main">Nebular hypothesis</span> Astronomical theory about the Solar System

The nebular hypothesis is the most widely accepted model in the field of cosmogony to explain the formation and evolution of the Solar System. It suggests the Solar System is formed from gas and dust orbiting the Sun which clumped up together to form the planets. The theory was developed by Immanuel Kant and published in his Universal Natural History and Theory of the Heavens (1755) and then modified in 1796 by Pierre Laplace. Originally applied to the Solar System, the process of planetary system formation is now thought to be at work throughout the universe. The widely accepted modern variant of the nebular theory is the solar nebular disk model (SNDM) or solar nebular model. It offered explanations for a variety of properties of the Solar System, including the nearly circular and coplanar orbits of the planets, and their motion in the same direction as the Sun's rotation. Some elements of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded.

<span class="mw-page-title-main">Rogue planet</span> Planetary objects without a planetary system

A rogueplanet, also termed a free-floating planet (FFP) or an isolated planetary-mass object (iPMO), is an interstellar object of planetary mass which is not gravitationally bound to any star or brown 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".

<span class="mw-page-title-main">2M1207</span> Brown dwarf in the constellation Centaurus

2M1207, 2M1207A or 2MASS J12073346–3932539 is a brown dwarf located in the constellation Centaurus; a companion object, 2M1207b, may be the first extrasolar planetary-mass companion to be directly imaged, and is the first discovered orbiting a brown dwarf.

<span class="mw-page-title-main">Planetary migration</span> Astronomical phenomenon

Planetary migration occurs when a planet or other body in orbit around a star interacts with a disk of gas or planetesimals, resulting in the alteration of its orbital parameters, especially its semi-major axis. Planetary migration is the most likely explanation for hot Jupiters. The generally accepted theory of planet formation from a protoplanetary disk predicts that such planets cannot form so close to their stars, as there is insufficient mass at such small radii and the temperature is too high to allow the formation of rocky or icy planetesimals.

<span class="mw-page-title-main">2M1207b</span> Planetary-mass object orbiting the brown dwarf 2M1207

2M1207b is a planetary-mass object orbiting the brown dwarf 2M1207, in the constellation Centaurus, approximately 170 light-years from Earth. It is one of the first candidate exoplanets to be directly observed. It was discovered in April 2004 by the Very Large Telescope (VLT) at the Paranal Observatory in Chile by a team from the European Southern Observatory led by Gaël Chauvin. It is believed to be from 5 to 6 times the mass of Jupiter and may orbit 2M1207 at a distance roughly as far from the brown dwarf as Pluto is from the Sun.

Eta Telescopii is a white-hued star in the southern constellation of Telescopium. This is an A-type main sequence star with an apparent visual magnitude of +5.03. It is approximately 158 light years from Earth and is a member of the Beta Pictoris Moving Group of stars that share a common motion through space. It is moving through the Galaxy at a speed of 23.7 km/s relative to the Sun.

<span class="mw-page-title-main">OTS 44</span> Celestial object in the constellation Chamaeleon

OTS 44 is a free-floating planetary-mass object or brown dwarf located at 550 light-years (170 pc) in the constellation Chamaeleon near the reflection nebula IC 2631. It is among the lowest-mass free-floating substellar objects, with approximately 11.5 times the mass of Jupiter, or approximately 1.1% that of the Sun. Its radius is not very well known and is estimated to be 23–57% that of the Sun.

<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.

HD 114762 b is a small red dwarf star, in the HD 114762 system, formerly thought to be a massive gaseous extrasolar planet, approximately 126 light-years (38.6 pc) away in the constellation of Coma Berenices. This optically undetected companion to the late F-type main-sequence star HD 114762 was discovered in 1989 by Latham, et al., and confirmed in an October 1991 paper by Cochran, et al. It was thought to be the first discovered exoplanet

<span class="mw-page-title-main">HD 100546</span> Star in the constellation Musca

HD 100546, also known as KR Muscae, is a pre-main sequence star of spectral type B8 to A0 located 353 light-years from Earth in the southern constellation of Musca. The star is surrounded by a circumstellar disk from a distance of 0.2 to 4 AU, and again from 13 AU out to a few hundred AU, with evidence for a protoplanet forming at a distance of around 47 AU.

HD 210277 b is an extrasolar planet orbiting the star HD 210277. It was discovered in September 1998 by the California and Carnegie Planet Search team using the highly successful radial velocity method. The planet is at least 24% more massive than Jupiter. The mean distance of the planet from the star is slightly more than Earth's distance from the Sun. However, the orbit is very eccentric, so at periastron this distance is almost halved, and at apastron it is as distant as Mars is from the Sun.

<span class="mw-page-title-main">CoRoT-3b</span> Brown dwarf or exoplanet orbiting CoRoT-3

CoRoT-3b is a brown dwarf or massive extrasolar planet with a mass 21.66 times that of Jupiter. The object orbits an F-type star in the constellation of Aquila. The orbit is circular and takes 4.2568 days to complete. It was discovered by the French-led CoRoT mission which detected the dimming of the parent star's light as CoRoT-3b passes in front of it.

<span class="mw-page-title-main">Extrasolar Planets Encyclopaedia</span> Astronomical database

The Extrasolar Planets Encyclopaedia is an astronomy website, founded in Paris, France at the Meudon Observatory by Jean Schneider in February 1995, which maintains a database of all the currently known and candidate extrasolar planets, with individual pages for each planet and a full list interactive catalog spreadsheet. The main catalogue comprises databases of all of the currently confirmed extrasolar planets as well as a database of unconfirmed planet detections. The databases are frequently updated with new data from peer-reviewed publications and conferences.

HD 16760 is a binary star system approximately 227 light-years away in the constellation Perseus. The primary star HD 16760 is a G-type main sequence star similar to the Sun. The secondary, HIP 12635 is 1.521 magnitudes fainter and located at a separation of 14.6 arcseconds from the primary, corresponding to a physical separation of at least 660 AU. Announced in July 2009, HD 16760 has been confirmed to have a red dwarf orbiting it, formerly thought to be a brown dwarf or exoplanet.

<span class="mw-page-title-main">Planetary-mass object</span> Size-based definition of celestial objects

A planetary-mass object (PMO), planemo, or planetary body is, by geophysical definition of celestial objects, any celestial object massive enough to achieve hydrostatic equilibrium, but not enough to sustain core fusion like a star.

<span class="mw-page-title-main">Circumstellar disc</span> Accumulation of matter around a star

A circumstellar disc is a torus, pancake or ring-shaped accretion disk of matter composed of gas, dust, planetesimals, asteroids, or collision fragments in orbit around a star. Around the youngest stars, they are the reservoirs of material out of which planets may form. Around mature stars, they indicate that planetesimal formation has taken place, and around white dwarfs, they indicate that planetary material survived the whole of stellar evolution. Such a disc can manifest itself in various ways.

<span class="mw-page-title-main">Circumplanetary disk</span> Accumulation of matter around a planet

A circumplanetary disk is a torus, pancake or ring-shaped accumulation of matter composed of gas, dust, planetesimals, asteroids or collision fragments in orbit around a planet. Around the planets, they are the reservoirs of material out of which moons may form. Such a disk can manifest itself in various ways.

References

  1. ↑ Hubert Klahr and Wolfgang Brandner (2006). Planet Formation: Theory, Observations, and Experiments. Cambridge University Press. ISBN   0-521-86015-6.
  2. ↑ Marcy, Geoffrey W.; Butler, R. Paul (February 2000), "Planets Orbiting Other Suns", The Publications of the Astronomical Society of the Pacific, 112 (768): 137–140, Bibcode:2000PASP..112..137M, doi: 10.1086/316516 , S2CID   123539686
  3. ↑ Kraus, Adam L.; et al. (May 2008), "Mapping the Shores of the Brown Dwarf Desert. I. Upper Scorpius", The Astrophysical Journal, 679 (1): 762–782, arXiv: 0801.2387 , Bibcode:2008ApJ...679..762K, doi:10.1086/587435
  4. ↑ Grether, Daniel; Lineweaver, Charles H. (1 April 2006). "How Dry is the Brown Dwarf Desert? Quantifying the Relative Number of Planets, Brown Dwarfs, and Stellar Companions around Nearby Sun-like Stars". The Astrophysical Journal. 640 (2): 1051–1062. arXiv: astro-ph/0412356 . Bibcode:2006ApJ...640.1051G. doi: 10.1086/500161 . ISSN   0004-637X.
  5. ↑ Fontanive, C.; Rice, K.; Bonavita, M.; Lopez, E.; Mužić, K.; Biller, B. (2019-06-01). "A high binary fraction for the most massive close-in giant planets and brown dwarf desert members". Monthly Notices of the Royal Astronomical Society. 485 (4): 4967–4996. arXiv: 1903.02332 . doi:10.1093/mnras/stz671. ISSN   0035-8711.
  6. ↑ Lubow, S. H.; Seibert, M.; Artymowicz, P. (1999). "Disk Accretion onto High-Mass Planets". The Astrophysical Journal. 526 (2): 1001–1012. arXiv: astro-ph/9910404 . Bibcode:1999ApJ...526.1001L. doi:10.1086/308045. S2CID   8619054.
  7. ↑ Kley, W.; Dirksen, G. (2006). "Disk eccentricity and embedded planets". Astronomy and Astrophysics. 447 (1): 369–377. arXiv: astro-ph/0510393 . Bibcode:2006A&A...447..369K. doi:10.1051/0004-6361:20053914. S2CID   7690026.
  8. ↑ Seager, Sara; Dotson, Renée, eds. (2010). Exoplanets. Tucson: University of Arizona Press. ISBN   978-0-8165-2945-2.
  9. ↑ Udry, Stéphane; Santos, Nuno C. (2007). "Statistical Properties of Exoplanets". Annual Review of Astronomy and Astrophysics. 45 (1): 397–439. arXiv: astro-ph/0306049 . Bibcode:2007ARA&A..45..397U. doi:10.1146/annurev.astro.45.051806.110529.
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