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Astronomers discover smallest-ever star, about the size of Saturn

Located about six hundred light years away, a star about the size of Saturn was recently discovered by a team of astronomers led by the University of Cambridge. Such a star is a possible candidate for Earth-sized planets which can have liquid water on their surfaces and support life.

The newly-discovered star is called EBLM J0555-57Ab and is around the size of Saturn, being the smallest-ever measured star, according to a University of Cambridge press release. The gravitational pull at its stellar surface is about 300 times stronger than what humans feel on Earth and astronomers found it with a method usually used to detect planets – scientists saw the star as it passed in front of its much larger companion.

The star was identified by WASP, a planet-finding experiment run by the Universities of Keele, Warwick, Leicester and St Andrews.

“Our discovery reveals how small stars can be. Had this star formed with only a slightly lower mass, the fusion reaction of hydrogen in its core could not be sustained, and the star would instead have transformed into a brown dwarf,” Alexander Boetticher, the lead author of the study, and a Master’s student at Cambridge’s Cavendish Laboratory and Institute of Astronomy, said.

He added that the star is smaller and likely colder than many of the gas giant exoplanets that have so far been identified.

This newly-measured star has a mass comparable to the current estimate for TRAPPIST-1, but has a radius that is nearly 30% smaller.

“The smallest stars provide optimal conditions for the discovery of Earth-like planets, and for the remote exploration of their atmospheres,” said co-author Amaury Triaud, senior researcher at Cambridge’s Institute of Astronomy.

These very small and dim stars are also the best possible candidates for detecting Earth-sized planets which can have liquid water on their surfaces, such as TRAPPIST-1, an ultracool dwarf surrounded by seven temperate Earth-sized worlds.

John Beckett