Saturday, January 7, 2017

Boom Star

If astronomers at Calvin College in Michigan are correct in five years we should be able to see the aftermath of an event that occurred almost 1800 years ago. Around the beginning of the third century A.D. a pair of stars in the constellation Cygnus spiraled into each other in a cataclysmic collision. No one on earth noticed, however, because the stars were 1800 light years distant, and the burst of light produced by the collision still hasn't arrived on earth. So how do we know this massive event even occurred? Sarah Knapton, science editor at the UK Telegraph explains:
At the beginning of the 3rd century civil war raged in Britain as the Roman emperor Septimius Severus sought to quell unrest in the north. But unknown to the fighting cohorts and Caledonian tribes, high above their heads two stars were coming together in a huge cataclysmic explosion.

Now 1800 years later the light from that collision will finally arrive on Earth creating a new star in the night sky - dubbed the ‘Boom Star - in an incredibly rare event which is usually only spotted through telescopes.

Before their meeting the two stars were too dim to be seen by the naked eye, but in 2022, the newly formed Red Nova will burn so brightly in the constellation Cygnus that everyone will be able to to see it.

“For the first time in history, parents will be able to point to a dark spot in the sky and say, ‘Watch, kids, there’s a star hiding in there, but soon it’s going to light up,” said Dr Matt Walhout, dean for research and scholarship at Calvin College, Michigan, where the prediction was made. For around six months the Boom Star will be one of the brightest in the sky before gradually dimming, returning to its normal brightness after around two to three years.
Knapton goes on to explain how the discovery was made:
In 2013 Professor Larry Molnar and his team at Calvin College noticed that the orbital speed [of the two stars as they orbited each other] was [increasing]. And doing so faster and faster.

It matched the data from another binary star which exploded in 2008 without warning and was picked up by astronomers. When experts went back over data from previous years they discovered that the crash could have been predicted because of the increasing orbital speeds.

“Observations of KIC9832227 show its orbital period has been getting faster since 1999 in the same distinctive way. We arrive at our predicted date by assuming the same process is happening here," said Prof Molnar, who is professor in astronomy.

“The star is around 1800 light years [away]. Hence if we are right about the upcoming outburst, it actually occurred 1795 years ago, and the light from the outburst has been travelling toward us ever since.

“Explosions of this size occur about once a decade in our Galaxy. This case is unusual in how close the star is and hence how bright we will see it shine and unique in that it is the first time anyone has predicted an explosion in advance.
No doubt amateur and professional astronomers alike will be competing to be the first to spot the explosion in Cygnus as the light completes its 1800 year journey and finally arrives on earth. It'll be fascinating, too, to see how close the Calvin team comes to predicting the time of arrival.

We might wonder if our own star, the sun, might ever collide with another star. It's one of the many fascinating properties of our sun that it happens to be located in a place in the galaxy that makes the possibility of a collision pretty remote. Note in the picture below of the Milky Way galaxy that there are vast regions of relatively empty space between the much more crowded spiral arms of the galaxy. Our sun and, of course, our earth are located in one of the regions between the spiral arms where the likelihood of collision is much reduced. So of all the bad things that can happen, collision with another star isn't likely, at least for a couple billion years or so.