Measurements of the physical properties of discs around young, low-mass stars have shown that many resemble our current picture for the early Solar system. Inner holes appear after a few times 10^6 yr, perhaps caused by the formation of large bodies such as planets, and high resolution imaging of young systems is beginning to constrain models of disc structure. There is considerable evidence that energetic mass loss is directly connected to accretion during star formation. Multiple knots and bow shocks in optical jets suggest accretion is far from steady, and there is clear evidence that jet directions wander on timescales of ~10^4 yr. An underlying driving jet is able to explain many features of the molecular outflows detected from deeply embedded protostars, but cannot account for the smooth conical structures observed for some older sources. A wide-angle wind may therefore also be needed.
Astrophysical Discs - an EC Summer School
- Pub Date:
- April 1999