A New Star on the Horizon

 
 

A new star is going to appear in our sky. Aoife Hardesty gives us the details.


FOR thousands of years humans have walked the Earth, and until recently, night was filled with darkness. Stars provided pinpricks of light in the inky dark and gave safety to travellers, aiding navigation.

In many religions and belief systems, stars have played roles of importance. The birth of Jesus was accompanied by a new star in the sky, and this star guided the three wise men to the Messiah. The native American Pawnee tribe’s creation myth says the first woman was created from the marriage of stars.

The Greeks named many constellations based on their mythology, the constellation Cygnus, was named for swans, and associated with stories of men or gods turning into swans for differing reasons, be it to escape justice or seduce maidens.

Stargazing as a science, or astronomy, has a long history all over the world, in particular China and the Middle East. It began with cataloguing the stars and planets, which allowed for a reference when new objects appeared in the sky. Some rare occurrences appear as bright new “stars” in the sky, and astronomers today often have a good idea how to classify them but not how to predict them.

One rare and interesting phenomenon is about to occur in our time; two stars are getting closer and closer together, and will soon collide and fuse together into one star, resulting in an explosion known as a Luminous Red Nova, which will be visible in 2022.

This star, which is being called a “Boom-star”, will appear in the constellation Cygnus, also known as the Northern Cross, and for roughly six months it will be one of the brightest objects in the night sky, although its brightness will fade over time.

The soon-to-collide stars are part of a binary star system called KIC9832227, the two stars orbit each other but they are currently too faint to be visible to the naked eye. They are 1,800 light years away, which means that the light from the stars takes 1,800 years to reach us here on Earth, so although we won’t see the results of their collision until 2022, the stars actually collided nearly 1800 years ago.

The two stars orbit each other every 11 hours but in 2013 Professor Larry Molnar and his team at Calvin College, Michigan, noticed that this orbital speed was decreasing. The orbit is getting faster and faster, signalling that the two stars would eventually collide.

“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.” said Professor Molnar.

“It’s a one-in-a-million chance that you can predict an explosion. It’s never been done before.”

This will not be the first Luminous Red Nova to occur, but it is the first time one has been predicted. In 2008, the binary star V1309 Scorpii unexpectedly resulted in a red nova. But studying data of the binary system collected prior to the explosion indicated that the time taken for the stars to orbit each other was decreasing.

This information is what enabled Professor Molnar and his team to predict the occurrence of another red nova for binary system KIC9832227.

The prediction of the red nova means that astronomers, professional and amateur alike can be on the look-out for the appearance of the boom star. The star will be roughly 10,000 times brighter than the binary system and will be easily visible to the naked eye, and so all members of the public will be able to search the skies and watch for the star.  And so, like our ancestors, we can turn to the skies to watch for a new star.

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