CFHT, Current Image of the Week


March 20th, 2000

Our Sun... a long long time ago?

Each week, discover a new spectacular image obtained at CFHT. Browse the archive

Our Sun... a long long time ago?

Credit: Image courtesy of G. Duvert & G. Duchêne (Observatoire de Grenoble, France) and F. Ménard (CFHT)

Stars are thought to form because molecular clouds collapse, due to gravity. In the process a hot central core develops, the protostar, surrounded by placental molecular gas and dust that has not been swallowed yet by the central star. The stars we catch in the formation process today are typically 1 million years old. They are babies! Our Sun is 5000 times older, at 5 billion years. These young stars are located in such star forming regions as the Taurus Molecular Cloud or The Orion Nebula, but also in many others.

More often than not, because our own Galaxy rotates and because an object that contracts while rotating also spins up. The material located around a young star then becomes flattened, it forms a disk. Compare with our own Solar System: all the planets are orbiting the sun almost in the same plane, probably tracing a common original environment that was also a disk, the so-called proto-planetary disk!

Today's research in star formation at CFHT focuses, amongst other things, on the discovery and study of forming stars and their circumstellar environment. This week's image features what the researchers think is a circumtellar disk seen close to edge-on around a very young star.

HV Tauri is a triple system, but one of the pair is too tight to be seen on the image (the bright star at bottom right). This star is know as HV Tau A/B since it is double. On the opposite corner of the image this week is HV Tau C, the third star of the triple system. It is separated by 4 arcsec from HV Tau A/B. All three objects are located in the Taurus Molecular cloud, about 450 light years away from us.

HV Tau C has a funny shape! It is literaly split in half by a dark lane. We believe this dark lane traces a proto-planetary disk that we see almost edge-on. This object was discovered independently by two teams of astronomers that used Adaptive Optics on the Canada-France-Hawaii Telescope. One of the discovery paper, by Monin & Bouvier (Observatoire de Grenoble also!), can be found here.

Chances are we will never see planets in this system, but its study will help understand how stars and planets form. For example, and directly measured from the image, the size of the disk can be evaluated. In this case, the disk has a radius of about 100 astronomical units (1 astronomical-unit is the distance between the Earth and the Sun). This is about twice the mean orbital radius of Pluto, the outermost planet in our Solar System. This disk would therefore be large enough to contain our Solar System. Computer models of this image will also allow to estimate the mass of the disk and check whether all the planets could have formed out of it or not.

Technical description:
This image was obtained in August 1999 with PUEO, CFHT's adaptive Optics system, equipped with the KIR infrared camera. It is the combination of four 60seconds images. The image shown here was obtained in the near-infrared K-Band, at 2.2 microns. Similar images are available in H- and J-Band, click here. No deconvolution or other restoration technique were applied to the image. The image has a resolution of 0.13arcsec, it is diffraction limited.

next week: A Strange Collection of Stars at the Galactic Center

editors: François Ménard & Jean-Charles Cuillandre
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CFHT is funded by the Governments of Canada and France, and by the University of Hawaii.