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).
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of the original nebular theory are echoed in modern theories of planetary formation, but most elements have been superseded.
A rogue planet, 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.
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".
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.
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.
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 forms a wide binary system with the star HD 181327 and has a substellar companion orbiting around it, named Eta Telescopii B.
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
Gliese 86 is a K-type main-sequence star approximately 35 light-years away in the constellation of Eridanus. It has been confirmed that a white dwarf orbits the primary star. In 1998 the European Southern Observatory announced that an extrasolar planet was orbiting the star.
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.
This page describes exoplanet orbital and physical parameters.
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.
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.
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.
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.
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.
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. They are reservoirs of material out of which moons may form. Such a disk can manifest itself in various ways.
