MOVIES OF DISK FORMATION AND DESTRUCTION
Harold W. Yorke (Jet Propulsion Laboratory / California Institute of Technology)
A slowly rotating, gravitationally unstable, density-peaked,
2 solar mass protostellar clump begins to collapse. After about
17000 years a central hydrostatic core forms which grows in mass
as material in the cloud continues to fall toward the center.
The kinetic energy of the infalling material is converted into
heat just above the surface of the protostar and this energy is
radiated away. This so-called accretion luminosity is responsible
for heating the immediate surroundings of the protostar and even
sporatically slowing down the infall - phases of reduced infall
lead to reduced accretion luminosity, which lead to reduced heating
and radiation pressure, which lead to a subsequent increase in infall.
Eventually, the infalling material has too much angular momentum
and it can no longer fall directly onto the protostar. A disk
forms. Angular momentum transport processes allow further accretion
through the disk. However, material in the outer disk regions gain
angular momentum and the disk grows in size and mass as even more
infalling gas hits the disk. Accretion shocks develop around the
accreting accretion disk.
Click on image to see each portion of the movie:
MPEG version of the evolution of the 2 solar mass case
Reference:
Yorke H.W., Bodenheimer 1999, ApJ, 525, 330
A 0.77 solar mass disk surrounding an 8 solar mass star interacts
with an isotropic central wind (1.E-8 solar masses per year at
50 km/sec) and with the central star's UV flux
(1.4E46 EUV photons/sec and 4.4E48 FUV photons/sec).
The outer layers of the disk are heated by the FUV photons and
expand. No longer gravitationally bound to the disk, this
"photoevaporation flow" interacts with the wind to produce
a "jet-like" feature. The EUV photons keep the "jet" ionized
and hot.
Click on image to see each portion of the movie:
Reference:
Yorke H.W., Richling, 2001, in preparation
Harold W. Yorke, Lead Scientist for Astrophysics
Jet Propulsion Laboratory,
California Institute of Technology
MS 169-506; 4800 Oak Grove Drive; Pasadena, CA 91109
e-mail:
Harold.Yorke@jpl.nasa.gov
(JPL clearance: CL002652)
