Astronomers have discovered a rare system of six young planets and a possible seventh planet dancing around a misbehaving baby star.
Not only will this system provide much-needed information about how planets form and develop around a baby star, but its similarity to the solar system may provide astronomers with a snapshot of what our cosmic neighborhood might have looked like nearly 4 billion years ago.
Six, possibly seven, exoplanets orbit a relatively nearby dwarf star in the Milky Way called TOI-1136; It is located approximately 270 light-years from Earth. The large number of exoplanets in the system inspired scientists to investigate further.
“Since very few star systems have this many planets, their sizes approach our solar system,” team member Tara Fetherolf, an adjunct professor of astrophysics at the University of California, San Francisco, said in a statement. “It’s both similar enough and different enough that we can learn a lot.”
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A rare young multi-planet star system with a hyperactive baby star
Scientists first studied the TOI-1136 planetary system in 2019 using NASA’s exoplanet hunter Transiting Exoplanet Survey Satellite (TESS). Fetherolf and his colleagues followed this initial work with observations made through multiple telescopes, revealing the masses and shapes of the planets. orbits and even the properties of their atmospheres.
The planets in the system, named between TOI-1136 b and TOI-1136 g, are classified as “sub-Neptunian” planets. The smallest of the six confirmed worlds is twice the width of Earth, while some of its sister planets are four times the size of our planet, about the size of the solar system’s ice giants Uranus and Neptune.
All of the TOI-1136 exoplanets are so close to their parent star that they complete an orbit in less than 88 Earth days. This is important because 88 days is the orbital period of Mercury, the closest planet to the Sun; This means that all these planets may be closer to their star than that little planet is to our star.
“These are strange planets to us because there is nothing exactly like them in our solar system,” said team member Rae Holcomb, who holds a Ph.D. in physics. candidate at the University of California, Berkeley, said in a separate statement. “But as we investigate other planetary systems further, we find that they may be the most common type of planet in the galaxy.”
What really makes TOI-1136 stand out is how young this planet and its central dwarf star are. TOI-1136 is only 700 million years old, which may seem very old, but compared to the 4.5 billion-year-old solar system and its star, the Sun, it makes the system a small child.
“This allows us to look at planets immediately after they form, and the formation of the solar system is a hot topic,” Fetherolf said. said. “Every time we find a multi-planet system, it gives us more information to inform our theories about how systems arise and how our system got here.”
Just like an overactive toddler, these young stars can be difficult to keep track of due to their hyperactivity. For toddler stars, this extreme activity manifests as intense magnetism, more widespread and intense sunspots, and increased solar flares.
The radiation emitted by baby stars not only makes them difficult to observe, but also shapes the planets that orbit them, especially their atmospheric properties.
“Young stars are always misbehaving. They’re very active, just like toddlers. This can make high-precision measurements difficult,” Stephen Kane, team leader and professor of planetary astrophysics at the University of California Riverside, said in a statement. . “This will not only help us make a head-to-head comparison of how planets change over time, but also show how their atmospheres develop at different distances from the star, which is perhaps the most important thing.”
Could any of TOI-1136’s planets host life?
Not only are the planets in the TOI-1136 system all relatively the same age, they are also close together in terms of physical distance. This gave researchers the chance to study something that is not easy to study in another planetary system.
“Normally, when we look for planets, we look for the impact of planets on their star. We watch the motion of the star and interpret that as the gravitational effects the planets have on it,” said Kane. “Here we can also see the planets attracting each other.”
This proximity allowed the team to detect a “resonance force” in the system, indicating that a seventh world could gravitationally influence the confirmed six.
Using the Automated Planet Finder telescope at the Lick Observatory on California’s Mount Hamilton and the High Resolution Echelle Spectrometer at the WM Keck Observatory on Hawaii’s inactive volcano Mauna Kea, the team was able to detect the planet’s “wobble.” The dwarf star TOI-1136 emerged when its planets pulled it.
Combining observations of this “wobble” with computer models and data of planets passing across the face of their stars allowed researchers to determine the planets’ masses with unprecedented precision.
“It took a lot of trial and error, but we were really pleased with our results after developing one of the most complex planetary system models to date in the exoplanet literature,” said UC Irvine Ph.D., lead author of the study. physics candidate Corey Beard said.
The first stirrings of life were believed to have emerged on Earth about 600 million years after the formation of the solar system, during a period of our planet’s history called the Archean. We see that the TOI-1136 system exoplanets are at a similar point in their history.
But the chances of planets in this system supporting life appear slim at best due to their proximity to their host star. This means that intense radiation from the star is likely stripping away the atmospheres of these worlds while boiling away liquid water, a crucial ingredient for life as we know it.
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“Are we rare? I am increasingly convinced that our system is extremely unusual in the universe,” said Kane. “Finding systems so unlike our own makes it increasingly clear how our solar system fits into the broader context of formation around other stars.”
The team now plans to further investigate the TOI-1136 system, confirm the seventh planet, and also determine the compositions of the planets’ atmospheres. This is something that can be achieved using the James Webb Space Telescope.
The team’s research was published in The Astronomical Journal.