Astrophysics

How Low Can You Go?

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Science  21 Feb 2003:
Vol. 299, Issue 5610, pp. 1151-1153
DOI: 10.1126/science.299.5610.1151d

It has been difficult to find the M dwarfs, which are the lowest mass, lowest temperature, and lowest luminosity stars that populate the darker corner of stellar life on the main sequence. Nonetheless, astronomers armed with bigger telescopes with better instruments and automated and efficient star surveys have found many M dwarfs over the past several years. Lepine et al. have now found the lowest of the lowly M dwarfs, a star named LSR 1425+7102. The star was originally observed in the Digitized Sky Survey, and follow-up spectroscopic observations show that the star has stronger CaH bands and weaker TiO bands, putting it in the M-subdwarf spectral class with a subtype index of 8.0. The star is extremely poor in metals, extremely cool, and has an estimated mass of only 0.09 times the mass of the Sun, the lowest-mass star found on the main sequence so far. Finding more of these meek M dwarfs will be important for understanding the origin and evolution of stars at the lower limits of their physically plausible masses. — LR

Astrophys. J. 585, L69 (2003).

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