By Tushna Commissariat

Astronomy and astrophysics has has advanced in leaps and bounds over the past few decades. As mankind attempts to foray further into the universe, it’s the little things that get by us sometimes.

Star formation is an area that has been well researched and studied and though we understand the ‘how’ and the ‘why’ of stellar genesis and evolution; it is very difficult to get visual evidence for theoretical data.

In our home galaxy, the Milky Way, there are an expected 100-400 billion stars. But weaving through this mass of stars are vast clouds of gas and dust that are generally referred to as the interstellar medium (ISM).

Now as much as the ISM might sound like a really cool name for dirt in space right out of Star Trek, it’s this very dust that obscures our views of new-born stars in visible light.

If we tune our instruments to look with longer wavelengths, especially where the Cosmic Microwave Background can be penetrated, lo and behold, a much clearer picture awaits us!

The dust no longer blocks the emission from the innermost regions of the galaxy and details previously unseen are revealed. New images from ESA ‘s Planck mission have revealed precisely this, isolating actual physical processes at work.

How does Planck mapping work?

Planck maps the sky in nine frequencies using two state-of-the-art instruments, designed to produce high-sensitivity, multi-frequency measurements of the diffuse sky radiation: the High Frequency Instrument (HFI) includes the frequency bands 100 – 857 GHz, and the Low Frequency Instrument (LFI) includes the frequency bands 30-70 GHz.

The first Planck all-sky survey began in August 2009 and will be completed by late-May 2010. Planck will gather data until the end of 2012, by which time it should complete four sky scans.

At the lowest frequencies, Planck notes emissions that occur due to relativistic electrons moving at relativistic speeds that interact with the Galactic magnetic fields (also known as synchrotron emissions), and that of free-free emission arising from electrons interacting with hot gas (they are called ‘free-free’ emissions as the electrons remain free even after they cause emission of a photon.).

At intermediate frequencies (corresponding to wavelengths of a few millimetres), the emission are mainly thermal emission of ionised gas heated by newly-formed hot stars.

At the highest frequencies, Planck maps the distribution of interstellar dust, including the coldest compact cores in the final stages of collapse towards the formation of new stars.

A star is made

Once stars are formed, they disperse the surrounding molecular clouds. An equilibrium between cloud collapse and dispersion regulates the number of stars that any given galaxy makes.

Various other physical phenomena influence this balance, including gravity, heating and cooling, turbulence, magnetic fields and more.

As a result of this interplay, the ISM rearranges itself into ‘phases’ which coexist side-by-side; so the molecular clouds that contain dense and cool gas and dust and the ‘cirrus’ containing more diffuse and warmer material.

The only way to accurately have data on the phases and constitutional elements of the ISM is to look at it through multiple frequencies; something that Plank can do.

As Plank can study all the mechanisms simultaneously, we can get data of all processes at the same time which is very beneficial. Also as it maps different areas; we can compare the difference seen in the ISM in a star forming area, such as the Orion Nebula with that seen in a low star formation area.

Recent images from Plank have shown us just that. For more information on the planck mission as we as star formation please visit the ESA Planck homepage.