A team of astronomers, led by Alexander Boetticher of the University of Cambridge have stumbled upon what is being touted as our galaxy’s smallest known star. According to experts, EBLM J0555-57Ab, (57-Ab), which is slightly larger than Saturn, is the smallest possible size for a star. Boetticher says, “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."
57-Ab, which lies almost 600 light years away from Earth, was discovered accidentally. The Cambridge team was looking for exoplanets using data from the Wide Angle Search for Planets (WASP), a planet discovery experiment created by a collaboration of universities. That’s when they noticed a tiny celestial object orbiting its parent star. They initially thought they had found an exoplanet. However, after studying its mass, the team realized that the dim orb was part of a binary star system – two stars of different masses orbiting one another.
The minuscule star is believed to be 2,000 to 3,000 times dimmer than our sun, possess a gravitational pull of about 300 times that of Earth, and sport a lower temperature than most similarly sized stars. The last fact is particularly intriguing to the scientists, who published their study in arXiv.org on July 12, 2017. That’s because ultra-cool stars like 57-Ab do not emit much heat and are, therefore, the best places to search for habitable planets. Earlier this year, an astrophysicist from Belgium’s University of Liège discovered the Trappist-1 system, which comprises seven potentially habitable planets rotating around an ultra cool star.
While stars like 57-Ab are ubiquitous, finding them is not easy. Study co-author Amaury Triaud says, “It is a little ironic that those small stars are the most common stars in the cosmos, but because they are faint, we don't know as much about them as we wish. This is why, in parallel to our investigations into planets orbiting ultra-cool stars, we are also investigating the stars themselves.” Whether this tiny star will finally end our search for aliens, remains to be seen. But for now, 57-Ab can bask in the glory of being the smallest star known to mankind!
Resources: phys.org, cam.ac.uk, arxiv.org