In Brief: An international team of astronomers,using the combined powers of two telescopes, were able to gain visibility over a supermassive star in our galaxy that is 30 times the size of the sun—and is still growing. Much can be learned about the lifespan of supermassive stars.
The massive young star, G11.92-0.61 MM1, or MM1 for short, is in our galaxy and reached its size faster than normal stars. Astronomers have their eyes on this young star which is around 11,000 light-years away from Earth, and for very good reasons.
“An average star like our Sun is formed over a few million years, whereas massive stars are formed orders of magnitude faster – around 100,000 years,” said team leader John Ilee, from the University of Cambridge in the UK.
The finding, published in the Monthly Notices of The Royal Astrological Society, is a rare one because while the dense clouds of molecular material make stellar nurseries perfect for birthing stars, those clouds of space dust make it very hard for normal telescopes to see through the clouds. Being able to watch this young star mature is an exceptional chance to monitor and better understand a massive star’s lifecycle.
Using the combined powers of the Submillimetre Array (SMA) in Hawaii and the Very Large Array (VLA) in New Mexico, which offer longer wavelengths than most telescopes, the team not only managed to spot the star but also to assess its surroundings.
Supermassive Star, MM1
At a young age, MM1 is already over 30 times the size of the Sun…and it’s still hungry. And it seems the MM1 still has a front seat to a full buffet, as calculations show a large disc of matter surrounding it. This is called a Keplerian disc, thus named for the law of motion it follows. Particles closer to the star move faster than those on the outer edges.
This disc implies that supermassive stars start out just like normal stars. “This type of rotation is also seen in the Solar System – the inner planets rotate around the Sun more quickly than the outer planets,” Ilee explained. “It’s exciting to find such a disc around a massive young star, because it suggests that massive stars form in a similar way to lower mass stars, like our Sun.”
So what else is on the table for MM1 (apart from lots of star food)? Well, death.
From what we know of stars, the faster they eat , the sooner they die. This makes finding them in their early stages of death by gluttony a rare occurrence. “These massive stars also burn through their fuel much more quickly, so they have shorter overall lifespans, making them harder to catch when they are infants,” Ilee says.
However, before MM1’s imminent demise, which would end up in either a supernova or a black hole, researchers want to use the Atacama Large Millimetre Array (ALMA) in Chile to confirm if the Keplerian disc around it is hiding more. “Our theoretical calculations suggest that the disc could, in fact, be hiding even more mass under layers of gas and dust,” says team member Duncan Forgan. “The disc may even be so massive that it can break up under its own gravity, forming a series of less massive companion protostars.”