What can we learn from a dusty old star system?

A highly detailed image of dusty disk around an old star is prompting astronomers to rethink their assumptions of about the characteristics of older stars.

Davide De Martin/Digitized Sky Survey 2/ESO
The background view shows the surroundings of aging stars IRAS 08544-4431 in the constellation of Vela (The Sails), with the inset showing the Very Large Telescope Interferometer reconstructed image, with the brighter central star removed.

With the help of a new imaging method using an advanced telescope, scientists can now see the sharpest ever images of the disks that surround old stars, which could provide new insight about the stellar lifecycle.

Our image provides the most detailed view into the heart of a dusty circumstellar disk to date,” the team wrote in a research letter published Wednesday in the journal Astronomy and Astrophysics.

This unprecedented detail has brought some new ideas into focus about the ability of older stars to "develop stable discs of gas and dust around them," according to a European Space Observatory press release.

Michel Hillen and Hans Van Winckel of the Belgium's Institute of Astronomy led a team of astronomers in utilizing the European Southern Observatory (ESO)’s Very Large Telescope Infrerometer (VLTI) in Chile to obtain the high quality images. The resolution of the images is so high that the scientists would be able to “determine the size and shape of a one euro coin seen from a distance of two thousand kilometres,” researcher Jacques Kluska explained in a University of Exeter press release.

Using the VLTI, the scientists directed their view at IRAS 08544-4431, an aging double star in the Vela constellation – also known as The Sails – in its post-asymptotic giant branch evolution period known as the protoplanetary nebula phase. This portion of medium-sized stars’ later life cycles includes rising temperatures and the creation of strong winds in the celestial bodies, which help create the surrounding disks.

The older of the two stars making up IRAS 08544-4431 is responsible for the material making up the dusty, gaseous disk that the researchers were interested in looking at. Such disks are not uncommon to find surrounding some younger stars, but astronomers had not yet been able to find older stars with similar features located close enough to Earth to be properly analyzed. The VLTI’s Precision Integrated-Optics Near-infrared Imaging ExpeRiment (PIONIER) instrument allowed light from the system’s four main telescopes to be combined to obtain pictures of unrivaled sharpness, focusing in on an old star’s dusty rings for the first time.

“It is really thanks to the jump in performance now provided by the new detector that we are able to view the very inner regions of this distant system,” Mr. Hillen said.

The researchers found that the disk's composition appears similar to that of the configurations that surround younger stars. Those disks are known to have the potential to form planets, but the possibility that older stars’ dusty halos could produce new bodies too is still unknown – although the new imaging method could produce more information in the future.

“Our observations and modelling open a new window to study the physics of these disks, as well as stellar evolution in double stars,” Mr. 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.”

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