Mysterious star deaths `may actually be mergers in disguise`

London: A swindling star, which that appeared to have exploded earlier this year, may have faked its own death to unite with a secret companion, researchers including one of Indian origin say.

If this is the case, the star joins a growing cast of eccentric stars that are suspected to be the products of stellar mergers, which have the potential to change our understanding of the universe’s chemical make-up. Stars are powered by nuclear fusion, converting hydrogen into helium in their cores. When very massive stars run out of hydrogen fuel, they start blending heavier elements until their cores collapse and they explode. These types of exploding stars, or supernovae, scatter the elements that go on to make new cosmic bodies. Since most of these stars detonate when they hit a set mass limit, their behaviour is fairly predictable, but a dying star can occasionally be seen going off the rails. Similar was the case with SN 2009ip, which flared up and died down for three years before finally seen going supernova in September. However, Noam Soker from the Technion-Israel Institute of Technology in Haifa has challenged the supernova interpretation of the outburst. Based on observations, he calculates that SN 2009ip generated less than 10 percent of the kinetic energy of a typical star explosion. “The more we look at it, the stranger its behaviour for a supernova,” New Scientist quoted him as saying. Instead, Soker and Amit Kashi from the University of Nevada in Las Vegas argue that the outburst has more in common with V838 Monocerotis - another flaring star now thought to be the result of a merger. The researchers think that the early outbursts from SN 2009ip were caused by two large stars brushing against each other. When they merged in September, they created a new star between 100 and 120 times the mass of the sun. According to Gijs Nelemans from Radboud University Nijmegen, Netherlands, astronomers are starting to realise how common star mergers must be. “We now know there is an extraordinary diversity of strange, transient objects,” he said. Nelemans concluded by saying that they can’t all be supernovae because of their widely different durations and brightness. ANI