Smallest-ever star is just a bit larger than Saturn
Staff Writer |
The smallest star yet measured has been discovered by a team of astronomers led by the University of Cambridge.
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With a size just a sliver larger than that of Saturn, the gravitational pull at its stellar surface is about 300 times stronger than what humans feel on Earth.
The star is likely as small as stars can possibly become, as it has just enough mass to enable the fusion of hydrogen nuclei into helium.
If it were any smaller, the pressure at the centre of the star would no longer be sufficient to enable this process to take place
Hydrogen fusion is also what powers the Sun, and scientists are attempting to replicate it as a powerful energy source here on Earth.
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.
The newly-measured star, called EBLM J0555-57Ab, is located about six hundred light years away.
It is part of a binary system, and was identified as it passed in front of its much larger companion, a method which is usually used to detect planets, not stars. Details will be published in the journal Astronomy & Astrophysics.
“Our discovery reveals how small stars can be,†said Alexander Boetticher, the lead author of the study, and a Master’s student at Cambridge’s Cavendish Laboratory and Institute of Astronomy.
“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.â€
EBLM J0555-57Ab was identified by WASP, a planet-finding experiment run by the Universities of Keele, Warwick, Leicester and St Andrews. EBLM J0555-57Ab was detected when it passed in front of, or transited, its larger parent star, forming what is called an eclipsing stellar binary system.
The parent star became dimmer in a periodic fashion, the signature of an orbiting object.
Thanks to this special configuration, researchers can accurately measure the mass and size of any orbiting companions, in this case a small star.
The mass of EBLM J0555-57Ab was established via the Doppler, wobble method, using data from the CORALIE spectrograph. ■