Michiel Hogerheijde Second-year Miller Fellow Dr. Michiel Hogerheijde uses molecules and dust particles in interstellar space to trace the formation of stars and planets. In this cold and dilute environment, the most common molecule, molecular hydrogen, does not emit any observable radiation. But up to a few hundred parts per million in these clouds consist of carbon monoxide, hydrogen cyanide, formaldehyde, silicon monoxide, carbon monosulfide, protonated nitrogen, the formyl ion, and other exotic molecules. These species do have emission lines observable at wavelengths of a few millimeter and shorter, associated with transitions between rotational energy levels. The intensity and shape of the emission lines provide valuable information on physical conditions in interstellar clouds, such as their density, temperature, and velocity field, and on their chemical composition.
Interstellar clouds are the nurseries of stars and planets.
As dense condensations inside these clouds become unstable against their own gravity, they collapse and form a star or a small group of stars. Around each star, the collapsing cloud forms an accretion disk through which material is funneled onto the star. It is thought that planets condense from the remains of such disks. Dr. Hogerheijde's research focuses on comparatively small condensations in star-forming clouds located in the constellations Taurus, Serpens, and Ophiucus. These regions form relatively isolated stars with masses up to that of our own Sun.