Using the European Space Agency’s Herschel Space Telescope and techniques more commonly encountered in Hollywood blockbuster computer graphics than in astronomy, a team of researchers has produced a three-dimensional map of the molecular cloud B68, a possible future birthplace for a low-mass star.
The team led by researchers from the Max Planck Institute for Astronomy (MPIA) also managed to identify a previously unobserved class of object that is likely the earliest known precursor of the birth of massive stars.
Stars are born in hiding, when dense regions within clouds of gas and dust collapse under their own gravity. But the clouds not only provide the raw material for star formation, they also absorb most of the light from their interior, hiding from view the crucial details of stellar birth -- one of the key astronomical processes if we want to understand our own origins.
Now, two groups in the EPoS (“Earliest Phases of Star formation”) project led by MPIA’s Oliver Krause, using ESA’s Herschel Space Telescope, report new results in understanding the earliest stages of star formation.
On the trail of the origin of low-mass stars (with less than about twice the mass of our Sun), a team led by Markus Nielbock (MPIA) has completed a detailed investigation of one of the best-known potential stellar birthplaces: the dark cloud (or “globule”) Barnard 68 in the constellation Ophiuchus.
Combining the Herschel Space Telescope’s unrivaled sharpness and sensitivity in the far-infrared range with a method more often encountered in visual effects companies working on Hollywood blockbusters than in astronomy, the researchers were able to construct the most realistic 3D model of the cloud to date.
The method, adapted for this particular use by MPIA’s Ralf Launhardt, uses what is known as ray tracing: For each minute portion of the object that we can see, the line of sight is traced back into the object itself.
The contribution by each portion of the light’s path -- is light being absorbed at this particular point? is it being emitted? if yes, at which wavelengths? -- are added up.
Ray tracing is routinely used to produce realistic-looking computer-generated creatures, objects or whole scenes. Here, it helped to match light emitted within Barnard 68 at different wavelengths with simplified models of the cloud’s three-dimensional shape, density and temperature distribution.
The results have shaken up some of what astronomers thought they knew about this cloud. The emerging picture is one of Barnard 68 condensing from a drawn-out filament, heated by unevenly distributed external radiation from the direction of the central plane of our home galaxy.
The astronomers also found some signs pointing to a cloud fragment in collision with Barnard 68, which might lead to the cloud’s collapse, and the formation of one or more low-mass stars, within the next hundreds of thousands of years, and whose existence had been predicted by a previous study (Burkert and Alves 2009).
As cosmic clouds go, Barnard 68 is rather small. Clouds of this size will give birth to a few low-mass stars at most. To find out how massive stars are born (mass greater than about twice the mass of the Sun), a team led by MPIA’s Sarah Ragan turned Herschel’s PACS camera to 45 significantly more massive dark clouds.
The clouds contain numerous stars about to be born, so-called “protostars”.
While previous missions, such as NASA’s Spitzer Space Telescope, have also searched for protostars, Herschel enables astronomers to probe deeper into the clouds than ever before. Younger protostars are hidden much more effectively within their clouds than older ones.
Herschel managed to find the youngest and most primitive protostars known.