Press Release

Perseus Molecular Cloud Is Full of Hot Air

By SpaceRef Editor
June 9, 2014
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The Canadian Astronomical Society / Société Canadienne D’Astronomie congratulates Dr. Andrew Pon for winning the CASCA/RASC Plaskett Medal for the best PhD thesis in astronomy and astrophysics for 2013. Dr. Pon completed his doctoral studies at the University of Victoria in 2013 under the supervision of Dr. Douglas Johnstone (UVic, NRC-Herzberg). His thesis, entitled “Shocks, Superbubbles, and Filaments: Investigations into Large Scale Gas Motions in Giant Molecular Clouds,” covers a wide range of topics in star formation — including gravitational collapse, turbulent heating, and galactic ecology.

Stars are known to form in giant clouds of molecular gas that are constantly churning with turbulent, internal motions. Vast quantities of energy are locked up in these turbulent motions, but little is known about what happens to this energy over a cloud’s lifetime. As part of his thesis, Dr. Pon and his collaborators have been studying how this energy leaves a molecular cloud and how observers on Earth could study this energy release.

Dr. Pon used complex computer simulations to calculate what happens when gas collides at supersonic speeds within star forming regions and was able to predict that such supersonic shocks should heat a small fraction (less than 1%) of all molecular clouds to ten times the typical temperature (a frigid 10 Kelvin) of the clouds. From such heated regions, Dr. Pon’s calculations predicted that the carbon monoxide molecule should radiate away most of a clouds turbulent energy.

Using the Herschel Space Observatory, Dr. Pon and his collaborators were able to observe a region within the nearby Perseus molecular cloud, in which thousands of young stars are forming. These observations have confirmed the presence of a hot gas component within the Perseus molecular cloud, potentially validating Dr. Pon’s theories for how the turbulent energy of a star-forming region escapes. Further observations of the carbon monoxide lines identified by Dr. Pon, using telescopes like the Atacama Large Millimeter Array, hold the potential to unlock further secrets about the important role that turbulence plays in the star formation process.

Press Contact:
Leslie Sage
CASCA Press Officer
+1 301 675 8957

Science Contacts:
Andrew Pon,

Paola Caselli
+49 89 30000-3400

Doug Johnstone

Dr. Pon is currently a postdoctoral researcher at the University of Leeds but will be starting a position at the Max Planck Institute for Extraterrestrial Physics in July, where he will continue his studies of turbulent dissipation and shock heating in molecular clouds. More details about this work can be found on Dr. Pon’s webpage (, in the Astrophysical Journal paper (, or in the MNRAS paper that will shortly be submitted.

SpaceRef staff editor.