A
maser, like a laser, is a source of bright electromagnetic radiation,
with the difference being that maser radiation is not optical light but
rather longer wavelength, microwave radiation. Small, dense molecular
clouds in interstellar space sometimes produce natural masers; water
vapor in clouds undergoing active star formation generates some of the
most spectacular such masers. In the most dramatic cases, a water vapor
maser can radiate more energy at a single wavelength than does the Sun
over its entire visible spectrum.
Masers are interesting in their own right, but also because their
bright emission provides a powerful diagnostic probe of regions where
massive star formation is still underway. CfA astronomer Nimesh Patel
and his colleagues have used a coordinated set of widely separated radio
telescopes (an interferometer) to study a dramatic region of star
formation about ten thousand light-years away, achieving a spatial
resolution of only a few hundred astronomical units (one AU is the
average distance of the Earth from the Sun). This spectacular precision
is possible because the masers are so bright.
The star formation region was known to have several clumps of young,
high mass stars accompanied by phenomena typically associated with such
star birth like powerful outflows and shocks. The astronomers combined
relatively recent and archival observations of masers in the region
spanning a period of about ten years, starting in 1999; the precision of
the data enabled them to detect the masers motion over this period.
The maser clusters, which are distributed over about a thousand AU, had
some clumps seen to move as much as fifty AU, corresponding to
velocities of about twenty kilometers per second (forty-five thousand
mph).
In the case of one bright region, the measurements over ten years
found that the material is tracing the shell of an outward-moving shock,
presumably propelled by radiation from the young star forming at the
center. The results confirm and extend detailed models of how newly born
massive stars affect their environment.
Reference:
"Multi-epoch
VLBA H2O Maser Observations Towards the Massive YSOs AFGL 2591 VLA 2
and VLA 3," J. M. Torrelles, M. A. Trinidad, S. Curiel, R. Estalella, N.
A. Patel, J. F. Gomez, G. Anglada, C. Carrasco-Gonz´alez, J. Canto, A.
Raga and L. F. Rodrıguez, MNRAS 437, 3803, 2014.
