2MASS J05325346+8246465 (abbreviated 2MASS J0532+8246) is possibly the first

brown dwarf Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main sequence, main-sequence stars. Their mass is approximately 13 to 80 Jupiter mass, times that of Jupiter ()not big en ...

observed in the

galactic halo A galactic halo is an extended, roughly spherical component of a galaxy which extends beyond the main, visible component. Several distinct components of a galaxy comprise its halo: * the stellar halo * the galactic corona (hot gas, i.e. a plas ...

of the Milky Way, and the first known substellar

subdwarf 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 ...

star. It was discovered from Two Micron All-Sky Survey data, and verified by observations at

Palomar Observatory The Palomar Observatory is an astronomical research observatory in the Palomar Mountains of San Diego County, California, United States. It is owned and operated by the California Institute of Technology (Caltech). Research time at the observat ...

and W. M. Keck Observatory. It has a low

metallicity In astronomy, metallicity is the Abundance of the chemical elements, abundance of Chemical element, elements present in an object that are heavier than hydrogen and helium. Most of the normal currently detectable (i.e. non-Dark matter, dark) matt ...

, which indicates it is an old star. The mass and temperature of 2MASS 0532+8246 makes it a rare object in stellar-substellar gap between conventional stars and brown dwarfs. It produces roughly half of its luminosity from hydrogen fusion. Such "gap" objects, covering a narrow range of masses but a wide range of temperatures, and powered by unsteady hydrogen fusion, are exotic but expected to be more common among low-metallicity objects like 2MASS J05325346+8246465. In 2008 it was discovered that this object is on a retrograde galactic orbit that is both eccentric and extends well away from the plane, making this object a member of the

. In 2024 this object was identified as a possible member of the Thamnos populations, together with the T subdwarf CWISE J113010.07+313944.7. Thamnos has two substructures called Thamnos 1 and Thamnos 2, both were identified in 2019 from

Gaia In Greek mythology, Gaia (; , a poetic form of ('), meaning 'land' or 'earth'),, , . also spelled Gaea (), is the personification of Earth. Gaia is the ancestral mother—sometimes parthenogenic—of all life. She is the mother of Uranus (S ...

data. Thamnos is likely the remnant of a

dwarf galaxy A dwarf galaxy is a small galaxy composed of about 1000 up to several billion stars, as compared to the Milky Way's 200–400 billion stars. The Large Magellanic Cloud, which closely orbits the Milky Way and contains over 30 billion stars, is so ...

that was accreted into the

Milky Way The Milky Way or Milky Way Galaxy is the galaxy that includes the Solar System, with the name describing the #Appearance, galaxy's appearance from Earth: a hazy band of light seen in the night sky formed from stars in other arms of the galax ...

and consists of metal-poor stars that formed between 8 and 12.89 billion years ago.

References

External links

Entry at DwarfArchives.org
{{DEFAULTSORT:2MASS J05325346+8246465 Camelopardalis Brown dwarfs L-type brown dwarfs J05325346+8246465 Free-floating substellar objects