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rfmcdonaldThe youngest star in our stellar neighbourhood has been found! AP Columbae, 27 light years away, is apparently a mere 40 million years old, closer to us in time than the dinosaurs.
Proxima Centauri is the outermost star of the Alpha Centauri trinary, the two largest and most Sol-like stars of which are 4.3 light years away.
AP Columbae is an obscure star very much like Proxima Centauri, in fact, in being a comparatively low-mass star prone to flares. (The paired capital letters of "AP" is standard nomenclature for variable stars). They differ in that whereas Proxima Centauri is a mature star some five billion years old, AP Columbae is formally classified as a pre-main sequence star, a star that has moved past the phase of generating most of its energy through gravitational attraction but has not yet begun to generate energy consistently through nuclear fusion like mature stars. Listed as AP Columbae at Wolfram Alpha but found under the additional label of LP 949-15 at the SIMBAD database, the star is in the rough direction of Sirius and Canopus in the northern hemisphere, but can be viewed only with fairly powerful telescopes.
The team's paper can be read here at ArXiv. As co-author Murphy points out, besides the novelty value the discovery is useful for those astronomers searching for young planets, worlds which should still be glowing hot from their formation.
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.
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.
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.
Proxima Centauri is the outermost star of the Alpha Centauri trinary, the two largest and most Sol-like stars of which are 4.3 light years away.
AP Columbae is an obscure star very much like Proxima Centauri, in fact, in being a comparatively low-mass star prone to flares. (The paired capital letters of "AP" is standard nomenclature for variable stars). They differ in that whereas Proxima Centauri is a mature star some five billion years old, AP Columbae is formally classified as a pre-main sequence star, a star that has moved past the phase of generating most of its energy through gravitational attraction but has not yet begun to generate energy consistently through nuclear fusion like mature stars. Listed as AP Columbae at Wolfram Alpha but found under the additional label of LP 949-15 at the SIMBAD database, the star is in the rough direction of Sirius and Canopus in the northern hemisphere, but can be viewed only with fairly powerful telescopes.
The team's paper can be read here at ArXiv. As co-author Murphy points out, besides the novelty value the discovery is useful for those astronomers searching for young planets, worlds which should still be glowing hot from their formation.
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.
