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Probing Stellar Nurseries

By David Reneke

David Reneke’s wrap-up of space and astronomy news.

An international team of astronomers has begun to map the location of the most massive and mysterious objects in our galaxy: the giant gas clouds where new stars are born. The team is searching for carbon monoxide as a marker of galactic clouds of molecular gas that can be up to 100 light years across.

“On Earth, carbon monoxide is poisonous, a silent killer, but in space it’s the second most abundant molecule and the easiest to see,” says team leader Prof Michael Burton of the University of NSW. “One of the largest unresolved mysteries in galactic astronomy is how these giant, diffuse clouds form in the interstellar medium. This process plays a key role in the cosmic cycle of birth and death of stars.”

The carbon monoxide survey of the southern Milky Way is being carried out with the 22-metre Mopra millimetre wave telescope at Coonabarabran. While the adjoining workshop, office, and accommodation wing were destroyed by bushfire in January, the telescope’s control room survived as it was encased in brick.

The team is also searching for “dark” galactic gas clouds that contain little carbon monoxide. It is assumed these clouds are mostly made up of molecular hydrogen, which is too cold to detect.

The team is using telescopes in Antarctica and Chile to search for these dark clouds, based on the presence of carbon atoms rather than carbon molecules. “Taken together, these three surveys will provide us with a picture of the distribution and movement of gas clouds in our galaxy,” Burton says.

Dark clouds, if found, could also be the missing source of gamma rays produced when high energy cosmic rays interact with the nuclei of gas atoms or molecules they encounter when travelling through space. The source of more than 30% of gamma rays remains unidentified, which is another big mystery this research could throw light on.

Some of the options for how large giant molecular clouds form include the gravitational collapse of an ensemble of small clouds into a larger one, or the random collision of small clouds that then agglomerate.

On average about one star per year is formed in the Milky Way, including stars similar to our own Sun. Stars that explode and die then replenish the gas clouds, as well as moving the gas about and mixing it up. It’s a natural and seemingly unending cycle of the Universe we were quite unaware of, even only a few decades ago.

Comet Impact Can Create Amino Acids

A team from Imperial College London, the University of Kent and Lawrence Livermore National Laboratory have discovered that when icy comets collide into a planet, amino acids can be produced. These essential building blocks are also produced if a rocky meteorite crashes into a planet with an icy surface.

In research published in Nature Geoscience, the researchers discovered that when a comet impacts on a world it creates a shock wave that generates molecules that make up amino acids. The impact of the shock wave also generates heat, which then transforms these molecules into amino acids.

The researchers suggest that this process helps to explain how life began on Earth 3.8–4.5 billion years ago after a period when the planet was bombarded by comets and meteorites.

Dr Zita Martins, co-author of the paper, says: “Our work shows that the basic building blocks of life can be assembled anywhere in the Solar System and perhaps beyond. However, the catch is that these building blocks need the right conditions in order for life to flourish. Excitingly, our study widens the scope for where these important ingredients may be formed in the Solar System and adds another piece to the puzzle of how life on our planet took root.”

Dr Mark Price, co-author from the University of Kent, added: “This process demonstrates a very simple mechanism whereby we can go from a mix of simple molecules, such as water and carbon dioxide ice, to a more complicated molecule, such as an amino acid. This is the first step towards life. The next step is to work out how to go from an amino acid to even more complex molecules such as proteins.”

The researchers believe that the abundance of ice on the surfaces of Enceladus and Europa, which are moons orbiting Saturn and Jupiter, respectively, could provide a perfect environment for the production of amino acids when meteorites crash into their surface.

The team made its discovery by recreating the impact of a comet by firing projectiles through a large high-speed gun. This gun, located at the University of Kent, uses compressed gas to propel projectiles at speeds of 7.15 km/sec into targets of ice mixtures with a similar composition to comets.

The resulting impact created amino acids such as glycine and alanine, an amino acid found in protein foods and synthesised by the body.

David Reneke is an astronomy lecturer and teacher, a feature writer for major Australian newspapers and magazines, and a science correspondent for ABC and commercial radio. Subscribe to David’s free Astro-Space newsletter at www.davidreneke.com