The process begins with the initial collapse of dense regions within cold interstellar molecular clouds. As these regions collapse under the weight of their own gravity, they fragment into stellar-size masses that tend to flatten out due to internal rotational motion. Eventually, the central regions settle down to become normal main sequence stars, but before they do, both the central star (or stars, in the case of multiple systems) and their surrounding material undergo a number of interesting transitions.
At first, the young protostar is surrounded by a large disk or torus of dense gas and dust. As the inner regions attempt to fall toward the protostar, much of the material is ejected in large-scale bipolar molecular flows. These are observed at millimeter wavelengths and can reach a parsec or more in length, and are studded with smaller blobs of luminous material, the Herbig-Haro objects. Because this phase of the process occurs while the star is still deeply embedded within the dark, obscuring material of the molecular cloud, very often the molecular flows and HH objects are the first indicators we have as to the existence and location of such protostars.
As this process continues, the stars eventually break out of their placental material and become visible. Traditionally, the newly-visible stars with masses like that of the Sun are called T Tauri stars, named after the prototype object of the class. A similar class of star, analogous to the TTs but at higher mass, are the Herbig Ae/Be stars, named after the astronomer who first indicated their importance as young pre-main sequence stars to the astronomical community.
Both the TTs and HAEBEs have emission at infrared wavelength far in excess of what can come from the stars themselves. Spectroscopic observations show that this material contains dust grains which are heated by the star, while high spatial resolution interferometric imaging at millimeter wavelengths shows that the dust is in a disklike structure, similar to that which is believed to have been present around the Sun when the planets formed.
Older stars, including many that are on the main sequence, still possess dusty debris disks which echoes of an earlier active time of possible planet formation. These stars, the "Vega-type" stars, are younger, more massive counterparts to the debris which still exists in our own Solar System. In our case, we see remnant dust and gases emitted by comets every time they approach the Sun, and the leftover debris of the comets and asteroids leaves a ghostly glow in the ecliptic plane called the Zodiacal Light. In some cases, we can actually see the zody disk light in these other stars. The disk of the star Beta Pictoris has been known since 1983. Now, many more are being imaged and studied, and in some cases their structure suggests the presence of Jupiter-mass planets, similar to those being discovered orbiting some nearby stars such as 47 UMa and 51 Peg.
One of the goals of my research is to understand the evolution of this disk material from the protostellar phase to the main sequence (including dust in our own Solar System) using infrared spectroscopy of the dust. In this way it may be possible to understand the history of the material that goes into forming the planets in both our own Solar System as well as other planetary systems.