Astronomers have discovered a rare system of six young planets and a possible seventh dancing around a misbehaving young star.
Not only could this system provide much-needed insight into how planets form and evolve around a young star, but its similarity to the Solar System could give astronomers a snapshot of what our cosmic environment might have looked like about 4 billion years ago.
The six, possibly seven, exoplanets orbit a relatively nearby dwarf star in the Milky Way called TOI-1136; it is located about 270 light-years from Earth. The large number of exoplanets in the system inspired scientists to conduct deeper research.
“Because few galaxies have as many planets as this one, it is close in size to our own solar system,” Tara Fetherolf, team member and visiting professor of astrophysics at the University of California, 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 galaxy with multiple planets and a hyperactive young star
Scientists initially studied the planetary system TOI-1136 using NASA’s exoplanet-hunting Transiting Exoplanet Survey Satellite (TESS) in 2019. Fetherolf and colleagues followed up this initial study with observations from multiple telescopes, examining the masses of the planets and the shapes of their planets were revealed. orbits, and even the characteristics of their atmosphere.
The planets in the system, with names between TOI-1136 b to TOI-1136 g, are classified as “sub-Neptune” planets. The smallest of the six confirmed worlds has a width twice that of Earth, while some of its sister planets are as large as four times our planet – about the size of the solar system’s ice giants Uranus and Neptune.
All of TOI-1136’s exoplanets are so close to their host star that they complete their orbits in less than 88 Earth days. This is important because 88 days is the orbital period of Mercury, the closest planet to the Sun, meaning all of these planets may be closer to their star than that little planet is to our star.
“They are strange planets to us because we don’t have anything exactly like them in our solar system,” said Rae Holcomb, team member and doctor of physics. candidate at the University of California, said in a separate statement. “But the more we study other planet systems, it appears that they may be the most common type of planet in the Milky Way.”
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 old, but compared to the 4.5 billion year old solar system and its star, the Sun, the system is a comparative toddler.
“This gives us a look at planets right after they form, and the formation of solar systems is a hotly debated topic,” says Fetherolf. “Every time we find a multi-planet system, it gives us more information to support our theories about how systems formed and how our system got here.”
Like an overactive human toddler, these young stars can be difficult to keep track of because of their hyperactivity. For toddler stars, this overactivity comes in the form of intense magnetism, more frequent and intense sunspots, and increased solar flares.
The radiation emitted by young stars not only makes them difficult to observe, but also shapes the planets that orbit them, especially shaping their atmospheric properties.
“Young stars misbehave all the time. They are very active, just like toddlers. That can make high-precision measurements difficult,” said Stephen Kane, team leader and professor of planetary astrophysics at the University of California Riverside, in the statement. . “This will help us make a one-to-one comparison not only of how planets change over time, but also how their atmospheres evolved at different distances from the star, which is perhaps most important.”
Could any of TOI-1136’s planets harbor life?
Not only are the planets in the TOI-1136 system all relatively the same age, but they are also all close together in terms of physical distance. This gave researchers the opportunity to investigate something that is not easy to study in another planetary system.
“Normally when we look for planets we look at the effect the planets have on their star. We look at how the star is moving and interpret that as the gravitational effects the planets have on it,” Kane said. “Here we can also see that the planets are pulling together.”
This proximity allowed the team to detect a ‘resonant force’ in the system that seems to indicate that a seventh world could be gravitationally affecting the confirmed six.
Using the Automated Planet Finder telescope at the Lick Observatory, located on Mount Hamilton in California, and the High-Resolution Echelle Spectrometer at the WM Keck Observatory on the inactive volcano Mauna Kea in Hawaii, the team was able to detect the ‘wobble’ of observe the earth. dwarf star TOI-1136 is caused by its planets pulling on it.
By combining observations of this ‘wobble’ with computer models and data of the planets crossing the front of their star, the researchers were able to determine the planets’ masses with an unprecedented level of accuracy.
“It took a lot of trial and error, but we were very pleased with our results after developing one of the most complicated planetary system models in the exoplanet literature to date,” lead study author and UC Irvine Ph.D. candidate in physics Corey Beard said.
It was believed that the first movements of life on Earth arose about 600 million years after the formation of the solar system, during a period in the history of our planet called the Archean period. We see the exoplanets of the TOI-1136 system at a similar point in their history.
However, the chances that the planets in this system could support life seem slim at best due to their proximity to their host star. This means the star’s intense radiation will likely strip the atmospheres of these worlds as liquid water boils away, a crucial ingredient for life as we know it.
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“Are we rare? I’m becoming increasingly convinced that our system is highly unusual in the universe,” Kane concluded. ‘Finding systems so different from 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 investigate the TOI-1136 system further, hopefully confirming the seventh planet and also determining the composition of the planets’ atmospheres. This is something that can be achieved using the James Webb Space Telescope.
The team’s research has been published in The Astronomical Journal.