Teeny-weeny star vies for title of smallest known

EBLM J0555-57Ab illustration

SHRIMPY STAR  The star EBLM J0555-57Ab (illustrated, right) is one of the smallest ever found, with a radius similar to Saturn’s. The star’s mass is just large enough that it can fuse hydrogen in its core.

Courtesy of Univ. of Cambridge

An itty-bitty star, with a radius about the size of Saturn’s, is one of the smallest ever found.

Known as EBLM J0555-57Ab, the star is significantly smaller than the Jupiter-sized TRAPPIST-1, a peewee star famous for hosting a septet of Earth-sized planets. And it’s comparable in size to a previously reported runt, 2MASS J0523-1403.

Although the star’s girth is similar to Saturn’s, it is much heftier, at almost 300 times Saturn’s mass. Still, that’s only about 8 percent of the sun’s mass, meaning that the star barely meets the qualifications for joining the stellar ranks, scientists report July 12 in Astronomy & Astrophysics. The star is just at the limit at which nuclear fusion can occur in a stellar core. If the star were less massive, it would instead be a failed star known as a brown dwarf.

The miniature star orbits another, larger star. Scientists with the Wide Angle Search for Planets, or WASP, collaboration detected the star with a method typically used to scout out exoplanets, watching it pass in front of its companion and dim the larger star’s light.

Read another version of this story at Science News for Students

Physics writer Emily Conover has a Ph.D. in physics from the University of Chicago. She is a two-time winner of the D.C. Science Writers’ Association Newsbrief award.

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