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Baby star found close to Earth

Astronomers have discovered Earth's closest infant star: a baby red dwarf, just 27 light-years away.

ASTRONOMERS HAVE DISCOVERED the closest known infant star to our planet, and it wasn't born until 25 million years after the extinction of the dinosaurs.

The star, called AP Columbae, is closer to Earth than previously thought and is around 40 million years old - a stellar newborn when compared to our own Sun which was created 4.6 billion years ago.

"The star has been known about and studied for the past 15 years, but it wasn't realised it was so young and so close, until now," says co-author Simon Murphy, a PhD student from the Australian National University in Canberra. He says that highly accurate measurements from telescopes in Coonabarabran, NSW, and Chile, Hawaii and California, allowed the international team to build a much better picture of the star.

How to measure a star

AP Columbae is classed as a red-dwarf star because it is relatively small - about a third the size of the Sun - and comparatively cool, with a surface temperature of about 3500ºC as opposed to the Sun's 6000ºC.

To measure the distance of the young star to Earth was relatively simple, Simon told Australian Geographic. As the Earth moved around in its natural orbit, the team observed how the position of AP Columbae changed in relation to stars in the background. "It's similar to when you're in a car, and the trees you see on the side of the road move at a different rate to the mountains in the background, depending on how far away they are," he says. "So with enough observations you can tie down the distance to a nearby star very accurately. But measuring the age is a little more tricky."

To calculate the approximate age of AP Columbae, the team - which included scientists from Georgia State University and the University of California, San Diego - analysed the amount of lithium in the star's atmosphere. Stars are born with a high level of lithium, but this declines rapidly with age.

On the hunt for gas giants

A distance of 27 light-years seems vast on a human scale, but on the scale of the stars it is a relatively short distance. The Milky Way itself spans 100,000 light-years from end-to-end, and our nearest neighbouring star of any age is Proxima Centauri, at just 4.2 light-years away.

The close proximity of AP Columbae makes it a prime candidate to hunt for orbiting gas giants, says Simon. "With any luck there'll be some newly formed planets around it...and [looking for them is] something we hope to do later in the year with telescopes in Chile."

If planets are found orbiting AP Columbae, it could help our understanding of how gas giants form. But it won't tell us much about Earth-like planets, says Simon, because they are too small to be spotted so far away.

Telescopes across the globe

Dr John Morgan, an astronomer from the International Centre for Radio Astronomy Research (ICRAR) in Perth, agrees that AP Columbae is likely to be the closest young star to Earth. "The significance here is that this is a young star," says John. "It hasn't yet reached middle age - [that's] the main sequence where stars spend most of their time."

John says that by exploring a range of techniques with telescopes positioned across the globe, the study has yielded measurements that are very reliable. "[The authors] have drawn on optical measurements with lots of different telescopes - even UV, X-ray and infrared measurements," he says. "Having that whole array of different techniques allows you to understand that star reasonably well."

With Australia's new SkyMapper telescope set to come online next year, "we'll be able to find a lot of other interesting objects including new, young stars that we just didn't know existed before," Simon says. The research is published this week in the Astronomical Journal.

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