Astronomers score most detailed view yet of a dying star's dusty disc

by Michelle Starr @riding_red

The Very Large Telescope in Chile captures the best image to date of the disc of dust and gas that forms around a star in the final stages of its life.

Stars are born and stars die, living out gargantuan life cycles book-ended by two stages of life that look, to our human eyes, fairly similar to one another.
Around a young star, you'll find a disc of gas and dust being drawn in by the star's gravitational pull. Around an elderly star, you'll find a ring of gas and dust moulted by the star, blown outward by stellar winds as it passes through the red giant phase of its life cycle.
As with any move performed in the incredible dance of the cosmos, Earth-based scientists would love to study these discs, compare them and learn more about the fascinating stages of stellar evolution. Young star discs are close, making them available for intense study. But old star discs nearby are few and far between.
Astronomers just got their best chance yet to study old star discs.

The disc being ejected by dying red giant IRAS 08544-4431. ESO/Digitized Sky Survey 2; Acknowledgement: Davide De Martin

The star in question is IRAS 08544-4431, an RV Tauri variable, a giant in the process of losing mass. It's located some 4,000 light-years from Earth in the direction of the constellation of Vela in the southern hemisphere. IRAS 08544-4431 is part of a binary system, in mutual orbit with a younger star.

This is the sharpest, most detailed view yet of a dying star's disc. It was captured by an international team of astronomers led by Michel Hillen and Hans Van Winckel of the Instituut voor Sterrenkunde in Leuven, Belgium.
To capture the star, the team made use of the Very Large Telescope in Paranal, Chile. They used its interferometer'sPrecision Integrated-Optics Near-infrared Imaging ExpeRiment instrument and newly updated RAPID detector. Moreover, a new imaging technique allowed the team to remove stars from the image to reveal what lies around them.

"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 metres would see," team member Jacques Kluska from the University of Exeterin the UK said Wednesday in a statement. "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 thousand kilometres."

This resolution allowed the team to see, for the first time, the inner edge of the ring around IRAS 08544-4431. In addition, they found a surprise: a fainter glow that is probably from an accretion disc around IRAS 08544-4431's companion star. This indicates that the companion star is taking material into its orbit, just as IRAS 08544-4431 is shucking it.
"Our observations and modelling open a new window to study the physics of these discs, as well as stellar evolution in double stars," Van Winckel said. "For the first time the complex interactions between close binary systems and their dusty environments can now be resolved in space and time."