Universiteit Leiden

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Anna wants to weigh solar systems

All the planets in our solar system orbit around the Sun in an ecliptical plane. This is to be expected because our solar system was formed from a so-called protoplanetary disc. PhD candidate Anna Miotello has studied these kinds of discs and how they influence the formation of stars and planets. PhD defence on 7 March.

What exactly are protoplanetary discs?

‘They are flat clouds in space made up of gas and dust. They are roughly the same shape as an LP, and the way they work can best be compared with the drain in your sink. The clouds orbit around a central point, a forming baby star that they are feed. Over time, planets could be formed in these clouds, which is what happened with our own solar system. But just how that star and these planets are created is still largely unclear. The most common theory is that dust particles clump together and eventually form a kind of baby planet, something that we call a planetesimal. Eventually, gas will be attracted around some of these planetesimal to form the gaseous planets.’

What has your research contributed to our understanding of this process?

‘I wanted to find a way of weighing protoplanetary discs. If we assume that these discs are the ingredients needed to make a cake, such discs need to weight at least as the final baked cake. In other words, a protoplanetary disc has to have at least the same mass as our whole solar system. To test this theory, I devised a model for calculating the mass of such discs based on the concentration of carbon monoxide.’

What conclusions can you draw from your research?

‘I applied my theory to the protoplanetary discs observed in the Lupus constellation, a relatively young region where stars and planets are currently being formed. According to my theory, such discs would have too little mass to be able to form a planetary systems like our own Solar System. That can’t be right. My suspicion is that we are unable to measure all the carbon monoxide found in the disc. It may be that a big part of the carbon is not in carbon monoxide, but it has already been absorbed into forming planets or more complex molecules that we can’t detect. That’s a good topic for further research.’

What interests you so much about planet formation?

‘I feel part of a true revolution. Until recently, we only knew about the existence of a few planets, those around our sun, but the universe around our own solar system was still largely a mystery. That’s still the case, but, thanks to all kinds of new instruments, we now know that basically each star hosts planets around her. Eventually this search will give us answers to fundamental questions about our own existence. Once we know how planets are formed, we will also know how Earth was formed. And maybe we’ll find out what it is that makes our planet  specifically able to sustain life.’

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