How big is really big in the world of stars?
By Amanda Jermyn



When it comes to stars, how big is big? The star we know best, our sun, is about 332,950 times the mass of the earth. That seems pretty massive! However, a team led by astrophysicist Paul Crowther of the University of Sheffield in England has recently discovered a star 265 times the mass of our sun, and shining 10 million times as brightly. In fact, it seems that in its infancy this star had 320 times the mass of our sun, before shedding some of its mass. It is also twice the mass of any other star ever discovered. Some stars, such as Red Giants, are larger in size, but they weigh far less. This newfound star, with the rather inelegant name of R136a1, is about 165,000 light years from our Milky Way, at the center of a star cluster in the Tarantula Nebula, a vast cloud of dust and gas in a galaxy called the Large Magellanic Cloud. Until this discovery, it was thought that stars could be no larger than 150 times the mass of the sun. Massive stars can be unstable, burning more brightly, and generating more pressure which ejects gas outward into space. The largest of them suffer from rapid burnout, lasting a mere three million years, compared to the 14 billion year life expectancy of our sun. They are also rare, as they can only form in very dense star clusters. Such large stars would be unlikely to have planets, and if they did, they would not be hospitable to life, at least not life as we know it. Such planets, if they existed, would be subject to intense radiation, and to the gravitational pull of other massive stars in the neighborhood that might eject the planets from their orbit.
So how, against all odds, can such massive stars exist? One theory posits that these stars might allow radiation to escape at one end while matter is sucked in at the other. It is also possible that they are really made up of smaller stars merging together, or that they are actually two stars in close proximity. According to the team that discovered R136a1, even if this were the case, the two stars would likely be very different sizes, with the larger one about 300 times the size of the sun at the time of its birth. For now, there is much about massive stars that remains a mystery. As Albert Einstein once said, “The most beautiful thing we can experience is the mysterious.”
If you’re in the mood for stargazing, consider attending Arunah Hill Days at the Arunah Hill Natural Science Center in Cummington from September 3rd to 6th. This free family-oriented weekend of astronomy will include stargazing, nature walks, GPS treasure hunts, rocket building, launching, and science education. On Friday night, Jim Zebrowski, NASA Solar System Ambassador, will speak on: “Arunah Hill and the Hubble Space Telescope celebrate 25 Years.” On Saturday night, Tim Barker, Professor of Astronomy at Wheaton College, will speak on “The Search for Life in the Universe.” For more information, visit www.arunah.org.