A rare system of planets and their young “hyperactive” star provide new insight into the development of solar systems
Astronomers have discovered a unique planetary system consisting of six young exoplanets, and possibly a seventh, orbiting the young star TOI-1136. This discovery not only helps advance understanding of the process of planet formation and evolution around young stars, but may also represent an analogue of our solar system in the early stages of its existence, about 4 billion years ago.
TOI-1136 — a nearby dwarf star in the Milky Way, located approximately 270 light years from Earth. Scientists are fascinated by this planetary system because of its rarity — Few systems have such a large number of planets. It is roughly comparable in size to our Solar System, and also has diversity and similarity, which allows discoveries about solar systems of similar configurations.
Original exploration of this planetary system began using NASA's TESS space telescope in 2019. But to obtain more detailed information, astronomers conducted long-term observations from various Earth telescopes to determine the mass of the planets, the shape of their orbit, and the characteristics of their atmosphere.
The planets in the TOI-1136 system from TOI-1136 b to TOI-1136 g are classified as sub-Neptunes. The smallest of the six planets already confirmed is twice the size of Earth, while the other planets discovered in this system are four times the size of Earth, similar to the ice giants Uranus and Neptune.
All planets in the TOI-1136 system orbit their star so closely that a complete revolution takes less than 88 Earth days. The period of revolution of the planet closest to the Sun — Mercury — is also 88 days. Studying these planets allows us to imagine that they are all closer to their star than Mercury is to the Sun.
The exoplanets in the TOI-1136 system are a unique class, distinct from those in our Solar System. However, as other planetary systems are studied, more and more scientists are inclined to think that this class of planets may be the most common in the galaxy, opening new horizons in understanding the cosmos.
However, the most interesting thing about TOI-1136 — this is the age of the planets and their stars. Just 700 million years makes them relatively young by cosmic standards. Compared to the solar system, which is about 4.5 billion years old, this system appears very young. This creates an unrivaled opportunity to study planets immediately after their formation and allows us to delve deeper into the process of the emergence and development of planetary systems, including the preconditions for the emergence of our own Solar System.
Also, young stars like TOI-1136 require special attention due to their hyperactivity. Due to the strong magnetism and intense sunspots and flares characteristic of young stars, these observations are of particular interest to the astronomical community.
The radiation emitted by young stars has a huge influence on the formation and evolution of the planets orbiting them. This activity of young stars creates special conditions for planets, affecting their atmospheric characteristics and changes that occur over time.
“Young stars constantly show their “excitability”, they are very active, like kids. This makes it difficult to make accurate measurements. However, such measurements not only allow us to compare changes on planets, but also to study how the atmospheres of these planets evolved at different distances from their star, which is one of the most important aspects in such studies», — noted Stephen Kane, group leader and professor of planetary astrophysics at the University of California.
One of the special aspects of the TOI-1136 system is that all of the planets in it are approximately the same age and are located very close to each other. This makes this system exceptional for research.
Thanks to the Automated Planet Finder telescope at Lick Observatory in California and the High-Resolution Echelle Spectrometer at the Keck Observatory on Mauna Kea in Hawaii, researchers were able to detect planetary wobbles. Analysis of these fluctuations using computer models and data on planetary transits made it possible to determine the masses of the planets with high accuracy.
«There was a lot of trial and error, but we are pleased with the results we obtained, creating one of the most complex models of exoplanetary systems to date», — noted the study's lead author and Ph.D. from the University of California, Irvine.
In our solar system, life arose approximately 600 million years after its formation during a period called the Archean. Astronomers are considering exoplanets of the TOI-1136 system in the early stages of their development. However, due to their proximity to their parent star, the chances that these planets could support life seem unlikely. The star's intense radiation likely destroys the atmosphere and evaporates liquid water, which is key to the development of life as we know it.
«I am increasingly coming to the conclusion that our system is unique in the Universe. The discovery of systems other than ours allows us to better understand how our solar system fits into the overall context of the formation of planetary systems around other stars», — Kane concluded.
Next, the team intends to continue studying the TOI-1136 system, hoping to confirm the presence of a seventh planet, as well as determine the composition of the planets’ atmospheres. This is what could be achieved with the James Webb Space Telescope.