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.
