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).
In astronomy, cataclysmic variable stars (CVs) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae, since ones with an outburst brightness visible to the naked eye and an invisible quiescent brightness appeared as new stars in the sky.
GQ Lupi b, or GQ Lupi B, is a possible extrasolar planet, brown dwarf or sub-brown dwarf orbiting the star GQ Lupi. Its discovery was announced in April 2005, less than a month before the full confirmation of 2M1207b was announced. Along with 2M1207b, this was one of the first extrasolar planet candidates to be directly imaged. The image was made with the European Southern Observatory's VLT telescope at the Paranal Observatory, Chile on June 25, 2004.
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.
A bipolar outflow comprises two continuous flows of gas from the poles of a star. Bipolar outflows may be associated with protostars, or with evolved post-AGB stars.
The study of extraterrestrial atmospheres is an active field of research, both as an aspect of astronomy and to gain insight into Earth's atmosphere. In addition to Earth, many of the other astronomical objects in the Solar System have atmospheres. These include all the giant planets, as well as Mars, Venus and Titan. Several moons and other bodies also have atmospheres, as do comets and the Sun. There is evidence that extrasolar planets can have an atmosphere. Comparisons of these atmospheres to one another and to Earth's atmosphere broaden our basic understanding of atmospheric processes such as the greenhouse effect, aerosol and cloud physics, and atmospheric chemistry and dynamics.
HR 8799 is a roughly 30 million-year-old main-sequence star located 133.3 light-years away from Earth in the constellation of Pegasus. It has roughly 1.5 times the Sun's mass and 4.9 times its luminosity. It is part of a system that also contains a debris disk and at least four massive planets. These planets were the first exoplanets whose orbital motion was confirmed by direct imaging. The star is a Gamma Doradus variable: its luminosity changes because of non-radial pulsations of its surface. The star is also classified as a Lambda Boötis star, which means its surface layers are depleted in iron peak elements. It is the only known star which is simultaneously a Gamma Doradus variable, a Lambda Boötis type, and a Vega-like star.
WD 1337+705 (G238-44) is a star in the constellation Ursa Minor. Shining with an apparent magnitude of 12.8, it is white dwarf 0.59 times as massive as the Sun. It is 86.5 light-years distant from Earth. It has 3% of the Sun's luminosity.
VHS J125601.92–125723.9 is a young triple brown dwarf system located in the constellation Corvus approximately 69.0 light-years from the Sun. The system consists of the equal-mass binary VHS J1256–1257AB and the distant planetary-mass companion VHS 1256–1257 b. In 2022, a continuous radio emission from the radiation belts surrounding VHS J1256–1257 was detected.
HD 169142 is a single Herbig Ae/Be star. Its surface temperature is 7650±150 K. HD 169142 is depleted of heavy elements compared to the Sun, with a metallicity Fe/H index of −0.375±0.125, but is much younger at an age of 7.5±4.5 million years. The star is rotating slowly and has relatively low stellar activity for a Herbig Ae/Be star.
WISE J080822.18-644357.3, also called J0808, is a 45+11
−7 Myr old star system in the Carina constellation with a circumstellar debris disk orbiting an M-type red dwarf about 331 lightyears from Earth.
EG Andromedae is a symbiotic binary in the constellation Andromeda. Its apparent visual magnitude varies between 6.97 and 7.80.
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.
A Peter Pan disk is a circumstellar disk around a star or brown dwarf that appears to have retained enough gas to form a gas giant planet for much longer than the typically assumed gas dispersal timescale of approximately 5 million years. Several examples of such disks have been observed to orbit stars with spectral types of M or later. The presence of gas around these disks has generally been inferred from the total amount of radiation emitted from the disk at infrared wavelengths, and/or spectroscopic signatures of hydrogen accreting onto the star. To fit one specific definition of a Peter Pan disk, the source needs to have an infrared "color" of , an age of >20 Myr and spectroscopic evidence of accretion.
GK Tauri is a young binary system composed of T Tauri-type pre-main sequence stars in the constellation of Taurus about 466 light years away, belonging to the Taurus Molecular Cloud.
DL Tauri is a young T Tauri-type pre-main sequence stars in the constellation of Taurus about 522 light years away, belonging to the Taurus Molecular Cloud. It is partially obscured by the foreground gas cloud rich in carbon monoxide, and is still accreting mass, producing 0.14 L☉ due to release of accretion energy. The stellar spectrum shows the lines of ionized oxygen, nitrogen, sulfur and iron.
HD 100453 is a binary star system which lies in the constellation Centaurus about 350 light years away from the Sun and is a member of the open cluster Scorpius–Centaurus association.
HD 163296 is a young Herbig Ae star that is surrounded by a protoplanetary disk. The disk is a popular target to study disk composition and several works suggested the presence of protoplanets inside the gaps of the disk.
Delorme 1 is a binary star with a planetary-mass companion (PMC) or protoplanet in a circumbinary orbit. The PMC is notable for showing signs of accretion, despite being 30-45 Myr old, making it similar to Peter Pan disks. These disks show characteristics of a gas-rich disk at unexpected high ages.
2MASS J11151597+1937266 is a young isolated planetary-mass object that is surrounded by a planetary disk.
