Astronomers have found the smallest star ever discovered

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University of Cambridge astronomers have discovered smallest known star in the universe and it’s almost Saturn-sized.

Name of this study is best explaining the star: “A Saturn-size low-mass star at the hydrogen-burning limit.” Name of this star is EBLM J0555-57Ab, and it is as small as star could possibly be. But don’t let that trick you it is also amongst densest active stellar objects in the universe, also the gravitational pull of the star is 300 stronger than Earth’s. And that means that it has enough mass to trigger the fusion of hydrogen nuclei into helium – he same fusion reaction that our sun is powered by.

“Our discovery reveals how small stars can be,” said Alexander von Boetticher, the lead author of the study, and a Master’s student at Cambridge’s Cavendish Laboratory and Institute of Astronomy, adding, “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.”

In spite of being big and hot, brown dwarfs do not have enough mass to tolerate stable hydrogen fusion at their cores. Because of that they are often referred to as “failed stars.” Unlike them, our tiny star was massive enough to meet the requirements and get a status of star.

EBLM J0555-57Ab’s predecessor was OGLE-TR-122b, a red dwarf, bigger than Jupiter, largest planet in our Solar system. EBLM J0555-57Ab, with its 0.081 solar masses just surpassed the limit as smallest theoretic star would be around 0.07 to 0.08 solar masses. This means that there could be even smaller stars somewhere in the universe.

The star was discovered using the transit method. It was spotted while passing in front of its larger companion, as it does on every 7,8 days. Measurements were detected by WASP, a planet-hunting initiative run by the Universities of Keele, Warwick, Leicester, and St. Andrews. Its location is about 600 light-years from Earth, it is part of a unique binary system.

Von Boetticher said “This star is smaller, and likely colder, than many of the gas giant exoplanets that have so far been identified,” adding, “While a fascinating feature of stellar physics, it is often harder to measure the size of such dim low-mass stars than for many of the larger planets. Thankfully, we can find these small stars with planet-hunting equipment, when they orbit a larger host star in a binary system. It might sound incredible, but finding a star can at times be harder than finding a planet.”

EBLM J0555-57Ab mass can be compared to mass of a TRAPPIST-1, a ultracool dwarf surrounded by 7 moderate world size of Earth, but radius of this star is about 30 percent smaller. Because of how small they are and their low brightness stars that have mass less than 20 percent of the Sun are difficult to be discovered, although they are probably common.

Taking into account they are present in great quantities, and that are mostly surrounded by large number of exoplanets, we should to find out more about them and learn more.