Free Astronomy Magazine September-October 2016

34 SPACE CHRONICLES s t ab l e o r b i t s were thought to be very unlike- ly. Located about 320 light-years from Earth in the constellation of Centau- rus (The Centaur), HD 131399Ab is about 16 million years old, mak- ing it also one of the youngest exo- planets discovered to date, and one of very few directly imaged plan- ets. With a temperature of around 580 degrees Celsius and an estimat- ed mass of four Jupiter masses, it is also one of the coldest and least massive directly-imaged exoplan- ets. “HD 131399Ab is one of the few exoplanets that have been di- rect- ly im- aged, and it's the first one in such an interesting dynam- ical configuration,” said Daniel Apai, from A surprising planet with three suns L u k e Skywa l k - er's home plan- et, Tatooine, in the Star Wars saga, was a strange world with two suns in the sky, but astronomers have now found a planet in an even more exotic sys- tem, where an observer would ei- ther experience constant daylight or enjoy triple sunrises and sunsets each day, depending on the sea- sons, which last longer than human lifetimes. This world has been dis- covered by a team of astronomers led by the University of Arizona, USA, using direct imaging at ESO’s Very Large Telescope (VLT) in Chile. The planet, HD 131399Ab, is unlike any other known world — its orbit around the brightest of the three stars is by far the widest known within a multi-star system. Such or- bits are often unstable, because of the complex and changing gravita- tional attraction from the other two stars in the system, and planets in by ESO SEPTEMBER-OCTOBER 2016