How Rare is Our Solar System?

How common is our Solar System? Less common than we might think.

A significant fraction of planetary systems around Sun-like stars have had a very dynamic past, culminating with the fall of planets into the central star.

But a new study involving Monash University astrophysicists sheds light on the scarcity of our Solar System, which has preserved its planets and kept them on nearly circular orbits, an arrangement conducive to life flourishing on Earth.

The research, published today in Nature Astronomy and led by Dr Lorenzo Spina at the National Institute for Astrophysics based in Italy, broadens our knowledge on the possible evolutionary paths of planetary systems, according to study co-author Parth Sharma, an Honours student at the Monash University School of Physics and Astronomy.

Regardless of the technology at our disposal, with millions of nearby Sun-like stars, the search for planets similar to our Earth will always look like the proverbial ‘needle in a haystack’,” said Parth.

However, our results open the future possibility of using chemical abundances to better identify stars that are likely to host Solar System analogues,” he said.

These findings represent a significant breakthrough in stellar astrophysics and exoplanet exploration.

The research refines search parameters for future investigation of potential planetary engulfment events, probes the origins of chemically weird stars, and tells us much about the evolution of solar systems, and planets, like our own.”

Stellar members of binary systems are formed from the same material, therefore they should be chemically identical. However, recent high-precision studies have unveiled chemical differences between the two members of binary pairs composed by Sun-like stars.

The very existence of these chemically inhomogeneous binaries represents one of the most contradictory examples in stellar astrophysics and source of tension between theory and observations.

It is still unclear whether the abundance variations are the result of chemical inhomogeneities in the protostellar gas clouds, or if they are due to planet engulfment events occurring after the star has formed,” said Parth.

The research team undertook a statistical study on 107 binary systems composed by Sun-like stars to provide – for the first time – unambiguous evidence in favour of the planet engulfment scenario.

They also established that planet engulfment events occurred in stars similar to our own Sun with a probability ranging between 20% and 35%.

This implies that a significant fraction of planetary systems undergo very dynamical evolutionary paths that can critically and disastrously modify their architectures, unlike our Solar System which has preserved its planets on nearly circular orbits,” said Parth.