Citizen scientists mining data collected by NASA’s Transiting Exoplanet Survey Satellite (TESS) discovered a record-breaking world and gave it a memorable nickname to match: Percival, after the father of Albus Dumbledore, headmaster of Hogwarts in the Harry Potter books. .
But in more formal terms, the extrasolar planet or “exoplanet” is called TOI 4633 c.
But there’s more to Percival than his relationship with the Dumbledores. The planet, which is about three times the size of Earth, orbits TOI 4633 A, a sun-sized star in a binary system located about 309 light-years from Earth. Earth also lies in this star’s habitable zone, a region with temperatures that are neither too hot nor too cold to allow liquid water to exist; This is where its other name comes from: “Goldilocks region.”
That’s why Percival is so special. Not only is it luckily in Goldilocks territory, but scientists believe there is a half-and-half chance of planets forming in systems with more than one star. And that’s not all.
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Additionally, Percival appears to have the longest orbit of its category of planets, namely Neptune-like planets. The exoplanet also has the second-longest orbit found in all TESS data so far, and is one of five worlds with orbits longer than 100 days that NASA has detected since the exoplanet-hunting spacecraft launched into space in 2018.
“This planet is remarkable in many ways,” Nora Eisner, of the Center for Computational Astrophysics and principal investigator of Planet Hunters TESS, said in a statement. “Its orbit is extraordinary, it’s extraordinary that it’s in the habitable zone, and it’s extraordinary that it’s orbiting a bright star.”
What do we know about this magical star system?
Percival was detected because it passed across the face or in front of the star TOI 4633, causing a small dip in light that TESS was sensitive enough to detect. The transit method is generally better at detecting planets that orbit close to their stars. This is because star-hugging planets are more likely to pass between Earth and their star as scientists monitor instruments, allowing us to detect a light-blocking arrangement more often.
Still, Percival is unusually far from its star for a transit-detected world, taking about 272 Earth days to orbit its star.
Ironically, scientists think there is another planet in this system, TOI 4633 b, which orbits closer to its parent star and takes only 34 Earth days to complete one revolution. However, this information was not confirmed because TOI 4633 b could not pass between its star and TESS, despite its proximity to its star. That’s why it can’t pass its star from our vantage point, and our instruments have difficulty analyzing it.
Part of the binary system is the star TOI 4633 B (uppercase letters represent stars, lowercase letters represent planets). It takes approximately 203 Earth years to orbit TOI 4633 A and the planets it orbits.
Binary stars form from the same cloud of gas and dust in a star system when cold, extremely dense regions “cluster” together and accumulate enough mass to collapse under their own gravity. If there is enough material, two stars can form. This is a binary system.
Planets are born from the matter left over after the creation of a star; This explains why if a cloud of material gives birth to two stars, it is also less likely to give birth to planets.
“Finding planets in multi-star systems is crucial to understanding how you can form different planets from the same material,” Eisner said. “It’s pretty exciting that we found this.”
Although Percival is located in the habitable zone of its star, it is frankly not very friendly to life as we know it. The planet probably doesn’t have a solid surface; Instead, it appears to consist of a thick atmosphere of water vapor, hydrogen, and methane, making it more of a gas giant in the solar system than a rocky Earth-like world. However, just as Jupiter and Saturn are suggested to have moons made of ice and rock that could support life, like Enceladus, there may be outer moons in Percival’s orbit that are more suitable for living things.
“If this planet had a moon, that moon would likely have a solid surface, which would then be a great place to find water,” Eisner said. said.
There is no sign of these exomoons yet, but the system would be a good choice for future exomoon detection campaigns thanks to the brightness of its stars and Percival’s long orbit; These factors are considered advantageous in exomoon detection.
Exploring new worlds from your home
Planet Hunters Citizen scientists of the TESS program help astronomers by filtering vast amounts of data that are impossible for researchers to handle alone. The program pays dividends; Its 43,000 volunteers from 90 countries have helped astronomers catalog nearly 25 million objects so far.
Massive Planet Hunters The TESS team is particularly adept at detecting faint signals from planets in long orbits that computer programs have difficulty identifying.
“The human brain has a truly incredible ability to recognize patterns and filter out noise,” Eisner said. “Our algorithms struggle to identify these long-period planets, while citizen scientists fail to do so.”
Percival’s discovery came as 15 Planet Hunter TESS citizen scientists identified for the first time a signal in the data indicating a transiting planet. Eisner and his team then took a closer look at the TOI 4633 system and detected small “wobbles” in the motion of one of the stars, which actually indicate the gravitational pull of the orbiting planets.
Taking a deeper look at the system using archival data collected over nearly 120 years, the team discovered that TOI 4633 consists of not one but two stars. However, these stars are now so close to each other that they cannot be distinguished separately.
It will take three decades for the stars TOI 4633 A and TOI 4633 B to reach large enough spacings for astronomers to determine the precise arrangement of this binary star system. This data could help determine whether the two planets are actually orbiting either star, which could help us better understand which star systems we should focus on as we continue to hunt for exoplanets.
“If we could constrain the orbits of planets, that could really offer a stepping stone to improving our understanding of exoplanet formation,” Eisner explained. “It may also someday help us look at a star and its properties and make some predictions about which planets are potentially orbiting in that system.”
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In the meantime, before more is known about this system, the Planet Hunter TESS team will continue to search for fascinating planets beyond the solar system.
“Every time I detect a possible transit, I can feel my heart beating faster and my excitement greatly increasing,” Simon Bentzen, a Danish citizen scientist who has been volunteering at Planet Hunters TESS since 2018, said in a statement. “I’m very happy to have helped come up with the new system.
“I hope that new planets can contribute to our understanding of planet formation and help answer other interesting planet-related questions.”
The team’s research was published Tuesday, April 30, in The Astrophysical Journal.