A common misconception is that space is “just space”, however the region between the stars in our universe is known as the “interstellar medium”. This interstellar medium consists of matter present due to the ever-changing nature of the universe.

The interstellar matter is comprised of mainly Carbon and Silicon based dust particles, which originate from many different sources, one such example could be that of a star at the end of its lifetime. These particles are dispersed into the interstellar void by the radiation emitted from the dying star, where they mix with gas molecules of varying composition.

It is at this point that scientists are particularly interested, as a variety of different interactions that can be observed on the interface between the dust particles and the gases that surround it.

To investigate these interactions scientists can attempt to recreate the conditions in space and use spectroscopy to investigate the reactions that occur at the dust-gas interface.

This is done using “Surface Analysis Techniques” at very low pressures (known as Ultra-High Vacuum or UHV) and low temperatures to recreate the conditions in space. These pressures are approximately 20 times lower than the pressure at the earth’s surface and the temperature can reach as low as -250°C.

A model surface similar to that of an interstellar dust particle is (for example, graphite is used to mimic a carbon based dust particle) exposed to gases under these conditions. Spectroscopic studies are then performed to analyse how different molecules behave.

These molecules can also become trapped within ices which form on the surface of the dust grains; leading to different properties within the spectroscopic evidence collected by scientists. Therefore allowing for a more complex analysis of the matter within the interstellar medium and it’s origins.

A prime example is the study of hydrogen, as it is the most abundant molecule in the interstellar medium. A common process that is observed is the formation of molecular hydrogen (a.k.a. H2 gas) from atomic hydrogen.

Hydrogen is not the only example; there is also helium, oxygen and a vast array of other more complex molecules within the interstellar medium.

Some of these more complex molecules may suggest that life could be present elsewhere in the universe, but more commonly can help us to understand the processes by which matter is recycled within the universe. As the interstellar matter dispersed from a dying star it ultimately ends up forming new stars and other cosmological bodies.

The study of cosmological matter uses a wide variety of techniques and surface based techniques are but are only the tip of the iceberg. Moreover, this field of study is important in our understanding of the way the universe was initially created, and how it continues to evolve.


James Martin


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