The nearly circular low inclination orbits of the planets have led
astronomers for centuries to consider Solar System formation within
a rotating disk. Thanks to advances in detection techniques at long
wavelengths sensitive to cool gas and dust, we now know that disks
are a natural consequence of the star formation process. When dense
cores in molecular clouds collapse, any small rotation is amplified
by conservation of angular momentum, which forms an accretion disk.
In addition, the star/disk system drives a powerful bipolar outflow
that simultaneously removes angular momentum to allow the protostar
to grow, and starts to clear away the surrounding core material.
Current models invoke magnetohydrodynamic processes to tap the
gravitational potential of the star/disk system to power the bipolar
outflow. Once the star is optically revealed, the remnant accretion
disk provides the raw material for making planets. Our knowledge of
disks and outflows is increasing rapidly, in part due to observations
from the Submillimeter Array that penetrate dusty environments and
reveal new details of the structures within.
Jes Jorgensen, Nimesh Patel, Lincoln Greenhill,
Jun-Hui Zhao, , Charles Lada,
Chunhua (Charlie) Qi, David Wilner, Eric E. Mamajek,
The disk around the nearby young star HD 163296 observed with the
Submillimeter Array. The position of the central star is indicated by the
star symbol. The contours show CO line intensity, which traces an
inclined disk of cool molecular gas, and the color scale represents
the line-of-sight velocity of the gas, from blue (approaching) to red
(receding), in a beautifully symmetric pattern of Keplerian motion. Image Source: Ph.D. thesis of Andrea Isella (Milan/Arcetri).