Royal Astronomical Society Press Release
RAS PN 10/31 (NAM 16) 14-Apr-2010
Towards the end of its life, in around 5 billion years time, our Sun will evolve into a red giant star. The temperature near the core will rise and the outer layers will expand to form a tenuous atmosphere a few hundred times the current radius of the Sun. Dust, which forms in this cool atmosphere, along with gas, is expelled from these types of stars during the aging process and forms the raw materials for the next generations of stars and planets. As the dust flows out into space it is shaped into beautiful nebulae by mechanisms that are not yet fully understood. Dusty discs can be created as a by-product of those mechanisms. Ultimately, nuclear fusion shuts down and the core of the dead star becomes a white dwarf.
Although these dusty discs are more than a hundred thousand million kilometres across (almost a thousand times larger than the orbit of the Earth around the Sun) they lie at such large distances from us that their apparent size is tiny. The discs can only be observed using a special technique in which telescopes are combined together to act like a giant zoom lens, dramatically increasing the sharpness of view. The astronomers used the Very Large Telescope Interferometer (VLTI) at the European Southern Observatory in Chile. This combines four giant telescopes, each with an 8.2-metre mirror, to create a telescope with the sharpness of view of one with a diameter of up to 130 metres. The VLTI also has the advantage of observing in the infrared, the part of the electromagnetic spectrum where the dusty discs shine brightly.
Top: Bipolar nebula M2-9 (B. Balick/HST) with a reconstructed image of its dusty disc observed by VLTI.
Bottom: Round nebula around Sakurai's Object (A. Zijlstra/University of Manchester) with its disc.