Ultra-cool dwarf

Size comparison between the sun (left) and the ultra-cool dwarf Trappist-1

Ultra-cool dwarf , engl. ultracool dwarf (abbreviated to UCD ) is a loose collective term for astronomical objects . They can be brown dwarfs , but also low-mass stars (red dwarfs) or objects of planetary mass .

According to a widespread convention today, the term “ultra-cool dwarf” subsumes objects with a spectral class of M7 and later, down to L and T dwarfs. This corresponds to an effective temperature of around 2700 Kelvin, surface gravity with log g in the range of around 5 and masses of less than a tenth of the solar mass .

Ultra-cool dwarfs represent about 15% of all astronomical objects in the stellar environment of the sun.

Examples

• Trappist-1
• SSSPM J0109-5101

literature

• Coryn Bailer-Jones, Ulrich Bastian (2004): The new spectral types L and T .; in: Stars and Space May 2004, p. 20. SuW0405-S20.pdf

swell

1. ↑ Blake et al. (2008): Near-Infrared Monitoring of Ultracool Dwarfs: Prospects for Searching for Transiting Companions ; in: Publications of the Astronomical Society of the Pacific 120 (870), pp. 860ff.
2. ↑ Justin R. Cantrell, Todd J. Henry, Russel J. White: THE SOLAR NEIGHBORHOOD XXIX: THE HABITABLE REAL ESTATE OF OUR NEAREST STELLAR NEIGHBORS . In: The Astronomical Journal . 146, No. 4, September 13, 2013, p. 99. arxiv : 1307.7038 . bibcode : 2013AJ .... 146 ... 99C . doi : 10.1088 / 0004-6256 / 146/4/99 .