Galactic Star Formation

Radio astronomers probe the interstellar medium (ISM) by observing molecular “signatures” that provide information about the temperatures, densities, chemical compositions, and velocities of the gases surrounding stars. Star-forming regions are dense with molecular clouds that gravitationally coalesce into hot, young stellar newborns. Scientists at Haystack use single-dish radio astronomy to observe molecules such as methanol (CH₃OH) in large regions containing numerous new stars.

VLBI techniques allow very high-resolution observations of emission from molecules such as silicon monoxide (SiO). These come in the form of masers—regions of gas and dust that send out laser-like beams of microwave radiation towards Earth. Masers can trace the velocities of outflows emanating from young protostars buried in opaque molecular clouds such as those in the Orion nebula.

Spectra of methanol masers detected with the Haystack 37-meter telescope. Their positions are identified on a carbon monoxide image of NGC 7538 [C.J. Davis, et al.]. The two spectra at each position are from two transitions of methanol. The line shapes indicate different physical conditions such as temperature and density. The 44 GHz line appears to be from maser emission while the 36 GHz line seems to switch from thermal to maser emission.

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