Astronomers find evidence of a new method of formation of giant planets

At the center of this image is the young star V960 Mon located more than 5,000 light-years away in the constellation Monoceros. Dusty material with the potential to form planets surrounds the star. Observations obtained with the ESO/ALMA (ESO/NAOJ/NRAO)/Weber et al.ESO/ALMA High Contrast Spectropolarimetric Exoplanet Research System

Some 30 years ago we could only imagine their existence, but after refining astronomical observation techniques, we now know of more than 5,000. And not only that, thanks to powerful observatories located all over the world and space telescopes, we can now analyze up to part of the chemical composition of its atmosphere. We are referring to exoplanets; those distant worlds that orbit stars other than the Sun.

Finding these planets not only gives humanity the opportunity to find a new home in the future, but also allows us to understand completely different planets than the 8 in our system. The last thing that astronomers have been able to observe is no longer the exoplanets themselves, but rather they are finding the first moments after the birth of these very distant planets.

There are currently two hypotheses about the formation of giant planets. One of them, and the best known, is that they arise from the accumulation of gases and dust left orbiting a newborn star. These accumulations, which are created in the protoplanetary disk, increase in mass while absorbing what is around them. Thus begins a positive feedback loop in which the planet absorbs more and more material due to the increase in the force of gravity that it exerts on its environment. In this way, over the course of millions of years, a large “rock” becomes a planetoid and, from there, when it meets a series of conditions, a planet.

However, a second hypothesis suggests that these planets would be formed by a “gravitational instability”. Said instability would be caused by the contraction and collapse of large fragments of material that surround the star, that is, a much faster and more violent process. This hypothesis had very little support in the scientific community, since evidence of this mechanism had never been found at a planetary level, until now. An international research team has published in The Astrophysical Journal Letters what appear to be the first direct observations of these gravitational instabilities.

In the constellation Monoceros, also known as “the unicorn” is a very young star called V960 Mon. This star is at a distance of 5000 light years and since 2014 it has been the subject of special interest because its brightness has increased by about 20 times. Since then, it has been discovered that the star is surrounded by a huge protoplanetary disk. During the early stages of their formation, protoplanetary disks do not have a clear shape around stars. That is to say, it is about huge amorphous clouds that orbit around a point.

As the planets mature inside the disk, thanks to their gravity they are able to “sweep” the orbits they will occupy from other small bodies. Thus, they will leave a trail in the form of a spiral around the star. To date, the James Webb Space Telescope has shown us some of these spectacular formations thousands of light-years away, and their number is expected to increase over the next few years. In addition to offering us a precious screensaver, the images obtained in these observations allow us to understand in greater detail how stellar systems evolve from their formation to maturity.

In the specific case of V960 Mon, you can see these spirals around it. In them, there are enormous accumulations of dust and gases that would have enough mass to end up forming giant planets. However, to fully understand this phenomenon, they need the data provided by other telescopes, as well as a higher resolution of the system that makes it possible to clearly distinguish the accumulations of stellar material.

Therefore, future observations will be made with instruments that are still being built in the Atacama desert, such as the Extremely Large Telescope (ELT). The ELT will be able to observe the system in more detail than ever before, and will help in gathering this much-needed information to understand the phenomenon. As Philipp Weber, an astronomer at the University of Santiago de Chile and principal investigator of the study, concludes: “The ELT will allow us to explore the chemical complexity that surrounds these clusters, helping us to find out more about the composition of the material from which they are forming, potentially, these giant planets.”

References (MLA):
Weber, Philipp, et al. “Spirals and Clumps in V960 Mon: Signs of Planet Formation via Gravitational Instability around a Fu Ori Star?” The Astrophysical Journal Letters, vol. 952, no. 1, 2023,