A step in the dark: dense molecular gas in galaxies

All the stars that exist in our Galaxy and in all other galaxies that are scattered throughout the Universe were formed
deep inside giant clouds of molecular hydrogen gas with sizes of hundreds of light years and masses of a million suns
or more. It is in such interstellar regions where dense hydrogen gas condenses via its self-gravity and cools down so it
can form the new stars and the planets around them, yet until now such regions have been mostly out of reach for astronomers.
This is simply because the cold interstellar gas does not emit radiation at optical wavelengths but at the much longer infrared (IR)
and millimetre and sub-millimetre wavelengths. Moreover, even if it did, any optical (and even IR) radiation from such regions
of interstellar space would be almost totally absorbed by the interstellar dust mixed with the molecular hydrogen of these
large gas clouds. Thus the now well-developed tools of optical and IR astronomy are unable to tell us anything about the
places where new Suns are created, and only a small smattering of millimetre and sub-millimetre telescopes have
been able to do so. One of them is the famed James Clerk Maxwell Telescope (JCMT) atop Mauna Kea in Hawaii
at 4092 meters altitude, built by the UK, with Canada and The Netherlands supplying many of its instruments.
The proposed project, initiated at the JCMT, will fully explore the properties of this important phase of interstellar
gas, and study its effects on the stars formed. It will take advantage of the truly new era that will open up in
observational astronomy with the now spaceborne Herschel Space Observatory, and the commissioning
of the Atacama Large Millimeter Array (ALMA) at 5100 meters altitude in the Atacama desert in North
Chile. The later, with 50 radiotelescopes of 12-meters diameter each is the largest ground-based observatory
on the planet and will at last give astronomers an unhindered view at mm/submm wavelengths. The proposed
study will help usher this new era by using these new facilities to study the most important component of the
Interstellar Medium, and its relation to the formation of stars in the Universe.