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Glossary term: subdwarf star

Description: A subdwarf is a class of star that is slightly fainter than a star of the same spectral type on the main sequence. Most subdwarfs lie below the main sequence due to their very low metal content. This changes how light and heat travel through their interiors and atmospheres, making them smaller, hotter and fainter. In the region of the Milky Way near the Solar System, subdwarfs are mostly members of the Galactic Halo. One such object is Barnard's star, the second nearest star system to the Solar System. There are also a small number of hot subdwarfs of spectral type B. These are thought to result from giant stars losing their outer layers for some reason. Astronomers aren't sure what causes this but one possible reason is a giant star having its outer layers stripped off by a binary star companion.

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Term and definition status: This term and its definition is still awaiting approval

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".