Skip to main content

Article Category

News

Article available in the folowing languages:

A tale of cosmic cannibalism

For the first time, scientists have discovered a planet that was formed in another galaxy. The detection of the newfound planet, which is similar in size to Jupiter, raises questions about planet formation and survival and offers clues to the possible fate of our own Solar Sys...

For the first time, scientists have discovered a planet that was formed in another galaxy. The detection of the newfound planet, which is similar in size to Jupiter, raises questions about planet formation and survival and offers clues to the possible fate of our own Solar System. The study, by researchers in Germany and the Netherlands, is published online by the journal Science. So far, astronomers have detected almost 500 exoplanets (i.e. planets lying outside our Solar System). The newly discovered planet orbits a star called HIP 13044, which lies some 2,000 light years away in the constellation of Fornax (the Furnace). The planet, dubbed HIP 13044 b, has a mass 1.25 times that of Jupiter. HIP 13044 b was detected via the radial velocity method, which measures tiny wobbles in a star that are caused by the gravitational pull of an orbiting planet. Although it is now part of the Milky Way, the newly discovered planet's origins appear to lie outside our own galaxy. Both the planet and its star were probably born in a dwarf galaxy that was devoured by the Milky Way between 6 and 9 billion years ago. According to the researchers, cases of 'galactic cannibalism' are not unusual; the remains of these galaxies form so-called 'stellar streams'. 'This is an exciting discovery,' comments Rainer Klement of the Max Planck Institute for Astronomy (MPIA) in Germany. 'For the first time, astronomers have detected a planetary system in a stellar stream of extragalactic origin. Because of the great distances involved, there are no confirmed detections of planets in other galaxies. But this cosmic merger has brought an extragalactic planet within our reach.' HIP 13044 b's discovery raises questions about the processes behind planet formation. Its parent star contains extremely low levels of any elements heavier than hydrogen and helium. 'It is a puzzle for the widely accepted model of planet formation of how such a star, which contains hardly any heavy elements at all, could have formed a planet,' says the first author of the paper, Johny Setiawan of the MPIA. 'Planets around stars like this must probably form in a different way.' The planet's survival is also something of a mystery for the astronomers. The star HIP 13044 has gone through the 'Red Giant' phase, during which it cools and expands massively. A star's planets are often engulfed by the star as it expands, and indeed there is evidence that HIP 13044 may have swallowed up some planets with smaller orbits. 'The star is rotating relatively quickly for an horizontal branch star,' explains Dr Setiawan. 'One explanation is that HIP 13044 swallowed its inner planets during the red giant phase, which would make the star spin more quickly.' Although HIP 13044 b survived the Red Giant phase of its star, it is by no means out of the woods yet; currently the star is in a calm phase which may last a few million years, but it is likely to expand again in the next stage of its evolution, possibly the planet. The findings have relevance for our own Solar System. 'This discovery is particularly intriguing when we consider the distant future of our own planetary system, as the Sun is also expected to become a red giant in about five billion years,' Dr Setiawan points out.

Countries

Germany, Netherlands

Related articles