ESO: First Detailed Image of Disc around Young Star

[bystander]

VLT Takes First Detailed Image of Disc around Young Star
European Southern Observatory | ann1058 | 09 Sept 2010

Disc around the young star HD 163296 (Credit: ESO/S Renard)

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New research carried out using ESO telescopes has, for the first time, allowed astronomers to reconstruct a detailed picture of the inner disc of matter around a young star. Stéphanie Renard of the Laboratoire d’Astrophysique de Grenoble and colleagues used the ESO VLT Interferometer to probe the secrets of the star HD 163296.

Young stars are surrounded by discs of dust and gas and scientists believe that it is in these discs that planets are born. Dusty grains in the disc stick to each other to make larger lumps that in turn also aggregate together. This growth is expected to continue until rocky bodies about the size of the Earth are formed.
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No single telescope currently in operation has vision acute enough to study such tiny and distant objects. The size of the region of the disc observed corresponds to 150 million kilometres — about the distance between the Earth and the Sun, but located at 360 light-years from Earth.

These very tiny details have an angular size of around 10 milliarcseconds — equivalent to trying to pick out small features on a road map held up 40 kilometres away. These minute angles are far smaller than any single telescope now operating can resolve.

To be able to image the inner part of the disc of matter close to the star, the team used a technique known as interferometry, in which sophisticated instrumentation combines the light from several telescopes into one observation. This increases the level of detail in the resulting pictures dramatically, although it does have some drawbacks: the results have to be reconstructed using complex mathematical algorithms because interferometry does not produce unambiguous images. But this difficult work is worthwhile as the resulting pictures tease out details far beyond the capabilities of the individual telescopes.

Milli-arcsecond images of the Herbig Ae star HD 163296 - S Renard et al

• Astronomy and Astrophysics 519 A26 (08 Sept 2010) DOI: 10.1051/0004-6361/201014910
  arXiv.org > astro-ph > arXiv:1007.2930 > 17 Jul 2010 (v1), 28 Jul 2010 (v2)

Strong near-infrared emission in the sub-AU disk of the Herbig Ae star HD 163296: evidence of refractory dust? - M Benisty et al

• Astronomy and Astrophysics 511 A74 (12 Mar 2010) DOI: 10.1051/0004-6361/200912898
  arXiv.org > astro-ph > arXiv:0911.4363 > 23 Nov 2009 (v1), 07 Dec 2009 (v2)

[Ann]

Interesting. This star is quite similar to Sirius in many ways, and it appears to be almost exactly as bright as Sirius. HD 163296 has a brightness of 22.4 +/- 5.4 times the luminosity of the Sun, giving it an absolute magnitude of 1.43 +/- 0.26. Sirius, which is so much more nearby, has a brightness of 21.79 +/- 0.18 times the luminosity of the Sun and an absolute magnitude of 1.454 +/- 0.009. And while Sirius is classified as an A0 main sequence star, HD 163296 is a main sequence star of class A1.

Sirius is noticably bluer than HD 163296, with a color index in Johnson of +0.009 versus +0.09 for HD 163296. But part of the color difference may easily be due to dust reddening. Sirius is much older than HD163296, old enough to have a white dwarf companion and old enough to have cleared away the dust disk that would have been there when the star was younger. HD163296, on the other hand, is a very young star, still surrounded by a dusty disk that will likely form planets in the future.

Personally I enjoy seeing astronomers find interesting dust disks and planets of stars of spectral class A, even though almost all of the efforts of astronomers is aimed at finding planets orbiting stars of class G, like the Sun.

Ann