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).
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.
A subdwarf, sometimes denoted by "sd", is a star with luminosity class VI under the Yerkes spectral classification system. They are defined as stars with luminosity 1.5 to 2 magnitudes lower than that of main-sequence stars of the same spectral type. On a Hertzsprung–Russell diagram subdwarfs appear to lie below the main sequence.
HD 195019 is a binary star system in the northern constellation of Delphinus. The brighter star has a close orbiting exoplanet companion. This system is located at a distance of 122 light years from the Sun based on parallax measurements, but it is drifting closer with a radial velocity of −91.3 km/s. Although it has an absolute magnitude of 4.01, at that distance the system is considered too faint to be viewed with the naked eye, having a combined apparent visual magnitude of 6.87. However, it should be readily visible with a pair of binoculars or a small telescope.
WISEPA J041022.71+150248.5 is a sub-brown dwarf of spectral class Y0, located in constellation Taurus. Being approximately 21.6 light-years from Earth, it is one of the Sun's nearest neighbors, especially assuming outdated parallax by Marsh et al., corresponding to even closer distance of approximately 14 light-years.
WISE J035000.32−565830.2 is a (sub-)brown dwarf of spectral class Y1, located in constellation Reticulum, the nearest known star/brown dwarf in this constellation. Being approximately 18.5 light-years from Earth, it is one of the Sun's nearest neighbors.
WISE J035934.06−540154.6 is a brown dwarf or sub-brown dwarf of spectral class Y0, located in constellation Reticulum. It is estimated to be approximately 44 light-years from Earth.
WISE J2000+3629 in astronomy is a nearby brown dwarf with a temperature less than 700 Kelvin, located in the constellation Cygnus. Parallax measurement suggest it is 24.4 light-years from Earth, making it one of the nearest known brown dwarfs to the Sun. It was discovered in 2014.
WISE J2209+2711 is a brown dwarf of spectral type Y0:, located in constellation Pegasus at 22 light-years from Earth. Its discovery was published in 2014 by Cushing et al.
Backyard Worlds: Planet 9 is a NASA-funded citizen science project which is part of the Zooniverse web portal. It aims to discover new brown dwarfs, faint objects that are less massive than stars, some of which might be among the nearest neighbors of the Solar System, and might conceivably detect the hypothesized Planet Nine. The project's principal investigator is Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center.
WISE 1534–1043 is a brown dwarf, Class Y, the coolest class, visible only in the infrared. It was accidentally discovered via the Wide-field Infrared Survey Explorer.
BD+60 1417b is a confirmed exoplanet discovered in the year 2021 using the imaging method. BD+60 1417b is the only known exoplanet in the system BD+60 1417, around 45 parsecs from Earth. BD+60 1417 is a young K0 star, while BD+60 1417 b has a late-L spectral type. The planet might be the first discovery of a directly imaged exoplanet found by a citizen scientist. Discovery of exoplanets involving amateurs are usually transiting exoplanets and are rarely discovered with other methods. Another example of a non-transiting exoplanet discovery by an amateur is the microlensing exoplanet Kojima-1Lb.
WISEA J181006.18-101000.5 or WISEA 1810-1010 is a substellar object in the constellation Serpens about 8.9 parsec or 29 light-years distant from earth. It stands out because of its peculiar colors matching both L-type and T-type objects, likely due to its very low metallicity. Together with WISEA 0414−5854 it is the first discovered extreme subdwarf (esd) of spectral type T. Lodieu et al. describe WISEA 1810-1010 as a water vapor dwarf due to its atmosphere being dominated by hydrogen and water vapor.
CWISEP J1935-1546 is a cold brown dwarf or planetary-mass object with a mass of 2-20 MJ or 6-35 MJ and a distance of 14.4 parsec.
CWISE J1055+5443 is a (sub-)brown dwarf with the spectral type of Y0 (pec). It is around 22 light years distant from earth.
Gliese 900 is a triple star system, located 68 light-years from Earth in the constellation Pisces. It is made up of three main sequence stars: one is a K-type star, the two others are M-dwarf stars. The two M-dwarfs form a binary system with a period of 36 years, and this system has a period of 80 years around the primary component. With an apparent magnitude of 9.546, Gliese 900 is not visible to the naked eye. A widely separated planet has been detected around the system.
