Astronomers discover galaxy's smallest star

Eloi Lecerf
Julho 12, 2017

Astronomers at the University of Cambridge have discovered a star that's barely bigger than Saturn, making it the smallest stellar object known to science.

Researchers from University of Cambridge in the United Kingdom identified the star located about six hundred light years away, called EBLM J0555-57Ab as it passed in front of its much larger companion.

EBLM J0555-57Ab is part of a binary star system, meaning two stars orbit a single point in space along with the system's planets.

"Our discovery reveals how small stars can be", said lead author Alexander Boetticher, a student at Cambridge's Cavendish Laboratory and Institute of Astronomy. The most famous example is TRAPPIST-1, a Jupiter-sized star that is home to seven planets.

Initially, the astronomers thought that it was an exoplanet. "While a fascinating feature of stellar physics, it is often harder to measure the size of such dim low-mass stars than for numerous larger planets".

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The small star is just slightly larger than Saturn, or 80 per cent the size of Jupiter, with a radius of 49,000 kilometres. This is dubbed as EBLM J0555-57Ab.

This star is smaller, and likely colder than numerous gas giant exoplanets that have so far been identified, researchers said.

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The star was detected when it passed in front of its much larger companion, which is unusual because the process is generally used to identify planets and not stars, informed Daily Mail.

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

TRAPPIST-1 is about the size of Jupiter, far smaller than our sun.

Astronomers will continue to use this method to detect small stars. It's somewhat hard to study this dwarf star due to the companion star's brightness.

"It's like trying to look at a candle beside a lighthouse", one of the team, Amaury Triaud, told Nicole Mortillaro at CBC News.

The team hopes this will shed some light on some of the most abundant stars in our universe.

"It is not entirely clear how stars with very different masses, like in our case, can form so close to each other", Triaud says.

"Most of the stars have the mass less one-quarter that of the sun ... although it's a bit on the smaller range, but it's part of the smallest stars that exist, which are the most common stars that exist". We might find an even smaller active star but given the rarity, it ought to take a while.

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