Astronomers have discovered a rare system of six young planets and a possible seventh dancing around a misbehaving infant star.
Not only could this system provide much-needed insight into how planets form and evolve around an infant star, but its similarity to the solar system could provide astronomers with a snapshot of what our cosmic neighborhood might have looked like about 4 billion years ago.
The six, and perhaps 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 has inspired scientists to conduct deeper research.
“Because few star systems contain as many planets as this one, it is close to the size of our solar system,” Tara Featherwolf, a member of the team and a visiting professor of astrophysics at the University of California, said in a statement. “They are 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 infant star
Scientists first studied the TOI-1136 planetary system using NASA’s Transiting Exoplanet Survey Satellite (TESS) in 2019. Featherwolf and his colleagues followed up this preliminary study with observations from multiple telescopes, revealing the masses and shapes of their planets. Their orbits, and even the characteristics of their atmospheres.
The planets in the system, which have names between TOI-1136 b to TOI-1136 g, are classified as “para-Neptunian” planets. The smallest of the six confirmed worlds is twice as wide as Earth, while some of its sister planets are up to four times the size of our planet – equivalent to the size of the solar system’s ice giants Uranus and Neptune.
All TOI-1136 exoplanets are so close to their parent star that they complete their 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, which means that all of these planets may be closer to their star than that little planet is to our star.
“They’re alien planets to us because we don’t have anything quite like them in our solar system,” said team member Ray Holcomb, a physics Ph.D. The UCLA candidate said in a separate statement. “But the more we study other planetary systems, the more it looks like they might be the most common type of planet in the galaxy.”
What makes TOI-1136 really special 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, it makes the system relatively young.
“This gives us a look at the planets right after they form,” Featherwolf said. “The formation of the solar system is a hot topic.” “Any time we find a multi-planet system, it gives us more information to inform our theories about how the systems came to be and how our system got here.”
Just like a hyperactive toddler, it can be difficult to keep track of these young stars due to their hyperactivity. For young stars, this excess activity comes in the form of intense magnetism, more widespread and intense sunspots, and increased solar flares.
The radiation from young stars not only makes them difficult to observe, but it also shapes the planets they orbit, sculpting their atmospheres in particular.
“Young stars misbehave all the time. They’re very active, just like toddlers. This can make high-resolution measurements difficult,” Stephen Kane, team leader and professor of planetary astrophysics at the University of California Riverside, said in the statement. . “This will help us not only make a one-to-one comparison of how planets have changed over time, but also how their atmospheres have evolved 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 relatively the same age, but they are all close to each other in terms of physical distance as well. This gave researchers an opportunity to examine something that is not easy to study in another planetary system.
“Normally, when we look for planets, we look at the effect of the planets on their stars. We watch the star move and interpret that as the gravitational effects that the planets have on it,” Kane said. “Here, we can also see the planets attracting each other.”
This proximity allowed the team to detect a “resonance force” in the system that seemed to indicate that the seventh world could gravitationally influence the confirmed sixth world.
Using the planet-hunting robotic telescope at the Lick Observatory, located on Mount Hamilton in California, and the high-resolution Eschel spectrometer at the W.M. Keck Observatory on the dormant volcano Mauna Kea in Hawaii, the team was able to detect the planet’s “wobble.” The dwarf star TOI-1136 caused its planets to be pulled onto it.
Combining observations of this “wobble” with computer models and data on planets crossing the face of their star has allowed researchers to determine planetary masses with an unprecedented level of accuracy.
“It took a lot of trial and error, but we were really happy with our results after developing one of the most complex planetary system models in the exoplanetary literature to date,” said the paper’s lead author, a Ph.D. from the University of California, Irvine. said physics candidate Corey Byrd.
It is believed that the first rudimentary movements of life appeared on Earth about 600 million years after the formation of the solar system in a period of our planet’s history called the Archean Eon. We see the TOI-1136 exoplanets at a similar stage in their history.
The chances of planets in this system being able to support life seem slim at best, due to their proximity to their host star. This means that intense radiation from the star would likely strip away the atmosphere of these worlds while boiling off liquid water, a crucial ingredient for life as we know it.
“Are we rare? I am increasingly convinced that our system is highly unusual in the universe,” Keane 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 intends to investigate the TOI-1136 system further, with the hope of confirming Planet Seven as well as determining 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.