The European Southern Observatory (ESO) has obtained the sharpest ever image of an old star’s disc, allowing researchers to understand better this mysterious phase in a star’s life.
The team, led by Michel Hillen and Hans Van Winckel from the Instituut Voor Sterrenkunde, was able to snap the ageing double star IRAS 08544-4431 located about 4,000 light-years from Earth in the constellation of Vela. The image reveals for the first time a well-defined ring extending far from the two stars, one of which is thought to be a red giant.
Similar discs are seen in young stellar systems, which ultimately give rise to planets. But astronomers had been unsure how or why they form around older stars. It’s possible that the material is blown from the star’s outer layers and can actually give rise to a second generation of planets. Studying this new system could provide some answers.
“We were also surprised to find a fainter glow that is probably coming from a small accretion disc around the companion star,” lead author Michel Hillen said in a statement. “We knew the star was double but weren’t expecting to see the companion directly. It is really thanks to the jump in performance now provided by the new detector in PIONIER, that we are able to view the very inner regions of this distant system.”
The astronomers used the Chile-based Very Large Telescope Interferometer to make the discovery, a system that allows scientists to combine the light obtained from four 8.2-meter (27 feet) telescopes and four 1.8-meter (6 feet) auxiliary telescopes into a single image.
“By combining light from several telescopes of the Very Large Telescope Interferometer, we obtained an image of stunning sharpness – equivalent to what a telescope with a diameter of 150 meters [490 feet] would see,” added team member Jacques Kluska. “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 2,000 kilometers [1,240 miles].”
Stars lose a significant amount of mass as they go through the red giant phase. The material is pushed away and sculpted by stellar winds, forming discs that resemble those that form planets around young stars. There are very few nearby old stars with such a disc, so this observation will allow researchers to better understand the differences between the disc formed at the beginning and at the end of the stellar cycle.
“Our observations and modelling open a new window to study the physics of these discs, as well as stellar evolution in double stars,” concluded Van Winckel. “For the first time the complex interactions between close binary systems and their dusty environments can now be resolved in space and time.”