The smallest star ever measured was discovered by a team of astronomers led by the University of Cambridge. With a size only a tiny bit larger than Saturn, the gravitational force on its stellar surface is about 300 times stronger than humans on Earth feel.
The star is probably as small as stars can possibly be, since it has enough mass to allow hydrogen nuclei to fuse into helium. If it were any smaller, the pressure at the center of the star would no longer be enough to allow this process to occur. Hydrogen fusion is also what powers the Sun, and scientists are trying to replicate it as a powerfulsource of power here on Earth.
These very small, faint stars are also the best possible candidates for detecting Earth-sized planets that may have liquid water on their surface, such as TRAPPIST-1, an ultracool dwarf with seven Earth-sized worlds.
The newly measured star, named EBLM J0555-57Ab, is located about 600 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 that is generally used to detect planets, not stars. The details will be published in the journal Astronomy & Astrophysics .
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"Our discovery reveals just how small stars can be," said Alexander Boetticher, the study's lead author and a master's student at the Cavendish Laboratory and Institute of Astronomy in Cambridge. "This star formed with only a slightly lower mass, the hydrogen fusion reaction at its core could not be sustained, and the star instead became a dwarfbrown."
EBLM J0555-57Ab was identified by WASP, an experiment that searches for planets across the Universities of Keele, Warwick, Leicester and St Andrews. EBLM J0555-57Ab was detected when it passed in front of or transited its largest parent star, forming what is called an eclipsed binary stellar system. The parent star was periodically dimmed in brightness, and the signature of an object inorbit became evident. 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 through the Doppler oscillation method, using data from the CORALIE spectrograph.
"This star is smaller, and probably cooler than many of the gas giant exoplanets that have been identified so far," von Boetticher said. "While a fascinating feature of stellar physics, it is often more difficult to measure the size of such low-mass stars than even for many of the larger planets. Fortunately, we can find these small stars withplanet-hunting equipment, when they orbit a larger host star in a binary system. It may sound incredible, but finding a star can sometimes be harder than finding a planet."
This newly measured star has a mass comparable to the current estimate for TRAPPIST-1, but has a radius that is about 30 percent smaller. "Smaller stars provide ideal conditions for the discovery of Earth-like planets, and for remote exploration of their atmospheres," said co-author Amaury Triaud, senior research fellow at the Cambridge Institute of Astronomy. "However, beforeto be able to study planets, we absolutely necessary to understand their star, which is fundamental."
Despite being the most numerous stars in the universe, stars with sizes and masses less than 20% of the mass of the Sun are poorly understood, as they are difficult to detect due to their small size and low luminosity. The EBLM project, which identified the star in this study, aims to connect this gap in knowledge. "Thanks to the EBLM project, we will be able to havea much greater understanding of the most common planets orbiting stars that exist, such as those orbiting TRAPPIST-1," said co-author Professor Didier Queloz of Cambridge' Cavendish Laboratory.
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Via: Phys
