New research reveals young planets are flattened structures rather than spherical

Astrophysicists from the University of Central Lancashire (UCLan) have discovered that planets have flattened shapes like smarties immediately after they form, rather than being spherical as previously thought.

The research, accepted for publication in Astronomy and astrophysics letters, shows that protoplanets, which are very young planets recently formed around stars, are flattened structures called oblate spheroids. The document is currently accessible on the arXiv preprint server.

The team, from UCLan’s Jeremiah Horrocks Institute of Mathematics, Physics and Astronomy, used computer simulations to model planet formation according to disk instability theory, which suggests that protoplanets form in short time frames from the breakup of large rotating disks of dense gas orbiting young stars.

Taking this approach, the team determined the properties of the planets, compared them to observations, and examined the mechanism of formation of gas giant planets. They focused on studying the shape of young planets and how these planets could become large gas giant planets, even larger than Jupiter. They also examined the properties of planets forming under various physical conditions, such as ambient temperature and gas density.

Dr. Adam Fenton, recently graduated Ph.D. student, led the research. He said: “Many exoplanets, which are planets orbiting stars in other solar systems outside our own, have been discovered over the past three decades. Although several thousand of them have been observed, how they form remains unexplained.

“They are thought to form either through “central accretion,” which is a gradual growth of dust particles that stick together to form larger and larger objects over long periods of time, or directly through the breakup of large disks. protostellars rotating around young stars in short time frames, what we call the theory of disk instability.

“This theory is attractive because large planets can form very quickly at great distances from their host star, which explains some observations of exoplanets.

“This was an extremely demanding computing project requiring half a million CPU hours on the UK’s DiRAC high-performance computing facility. But the results were astonishing and well worth the effort.”

Dr Dimitris Stamatellos, reader in astrophysics at UCLan and co-researcher, said: “We have been studying planet formation for a long time, but never before have we thought about checking the shape of planets as they develop. They are formed in the simulations. always assumed they were spherical.

“We were very surprised that they were oblate spheroids, quite similar to smarties.”

Observational confirmation of the flattened shape of young planets could answer the critical question about how planets form, pointing to the currently less favored disk instability model rather than the standard theory of planet formation by accretion of the nucleus.

The researchers also found that new planets grow as material falls on them, primarily from their poles rather than their equators.

These findings have important implications for observing young planets, because they suggest that how planets appear through a telescope depends on the viewing angle. Such observations of young planets are important for understanding the mechanism of planet formation.

Researchers are pursuing this discovery with improved computer models to examine how the shape of these planets is affected by the environment in which they form and to determine their chemical composition for comparison with future observations from the James Webb Space Telescope (JWST). ).

Observing young planets has become possible in recent years thanks to observation facilities such as the Atacama Large Millimeter Array (ALMA) and the Very Large Telescope (VLT).