Free Astronomy Magazine May-June 2016

SPACE CHRONICLES enough for us to obtain detailed images. But this has now changed. A team of astronomers led by Michel Hillen and Hans Van Winckel from the Instituut voor Sterrenkunde in Leuven, Belgium, has used the full power of the Very Large Telescope Interferometer (VLTI) at ESO’s Para- nal Observatory in Chile, armed with the PIONIER instrument, and the newly upgraded RAPID detector. Their target was the old double star IRAS 08544-4431 (detected and cata- logued by the IRAS satellite observa- tory in the 1980s), lying about 4000 light-years from Earth in the south- ern constellation of Vela (The Sails). This double star consists of a red giant star, which expelled the material in the sur- rounding dusty disc, and a less-evolved more normal star or- biting close to it. Jacques Kluska, team member from the University of Exeter, United Kingdom, ex- plains: “By combin- ing light from sev- eral telescopes of the Very Large Tele- scope Interferometer, we obtained an image of stunning sharpness — equivalent to what a telescope with a diameter of 150 metres would see. The resolution is so high that, for comparison, we could determine the size and shape of a one euro coin seen from a distance of two thou- sand kilometres.” Thanks to the unprecedented sharp- ness of the images (about one mil- liarcsecond) from the Very Large Telescope Interferometer, and a new imaging technique that can remove the central stars from the image to reveal what lies around them, the team could dissect all the building blocks of the IRAS 08544-4431 sys- tem for the first time. The most prominent feature of the image is the clearly resolved ring. The inner edge of the dust ring, seen for the first time in these observa- tions, corresponds very well with the expected start of the dusty disc: clos- er to the stars, the dust would evap- orate in the fierce radiation from the stars. T his video takes the viewer deep into a spectacular region of the southern Milky Way in the constella- tion of Vela (The Sails). We pass many interesting ob- jects, including star formation regions and the blue filaments of a supernova remnant, before closing in on the faint star IRAS 08544-4431. This aging object is sur- rounded by a dusty disc that has been clearly resolved for the first time by the Very Large Telescope Interfer- ometer at ESO’s Paranal Observatory in Chile. [ESO/ Digitized Sky Survey 2/N. Risinger (skysurvey.org)] “We were also surprised to find a fainter glow that is probably coming from a small accretion disc around the companion star. We knew the star was double, but weren’t expect- ing to see the companion directly. It is really thanks to the jump in per- formance now provided by the new detector in PIONIER, that we are able to view the very inner regions of this distant system,” adds lead au- thor Michel Hillen. The team finds that discs around old stars are indeed very similar to the planet-forming ones around young stars. Whether a second crop of plan- ets can really form around these old stars is yet to be determined, but it is an intriguing possibility. “Our observations and modelling open a new window to study the physics of these discs, as well as stel- lar evolution in double stars. For the first time the complex interactions between close binary systems and their dusty environments can now be resolved in space and time,” con- cludes Hans Van Winckel. n