Does dust help or hinder star formation?
Dust has an important role in star formation. It protects the molecules in the dense gas from the ultraviolet photons emitted by the massive young stars. Without dust, the molecules would be broken and the atoms ionised. In star-forming regions there are a lot of these young stars formed in nearby clouds. The newly formed stars can thus reduce the capability to form new stars. This is why dust has an important role to help the formation of dense molecular clouds by protecting them.
In contrast, while not hindering star formation, dust is limiting our capability to measure star formation. When spectroscopy is not available – which is often the case in very distant galaxies – we estimate the amount of stars formed per year in a galaxy from the ultraviolet light they emit, since it comes mainly from massive short-lived stars.
The main problem is that dust is very efficient at absorbing the ultraviolet light.
We have to correct for this phenomenon. We can deduce the energy absorbed by it using the thermal emission of this cold dust. This is usually a few tens of degrees above absolute zero and even less for distant galaxies because of the redshift effect. This is why far-infrared and submillimeter telescopes, which probe the emission of these cold bodies, are so important for understanding the star formation history in the universe. Dr Matthieu Bethermin is a assistant astronomer at Laboratoire d'Astrophysique de Marseille, France