Astronomers report the discovery and validation of two long-period giant exoplanets orbiting the K-dwarf star TOI-4600, first detected using observations from NASA’s Transiting Exoplanet Survey Satellite (TESS). One of these planets, TOI-4600c, orbits its star once every 482.8 days, making it the longest-period confirmed or validated planet discovered by TESS to date.
An artist’s rendition of the two exoplanets and their parent star in the TOI-4600 system. Image credit: Tedi Vick.
TOI-4600 is located approximately 815 light-years away from Earth in the constellation of Draco.
Also known as TIC 232608943 and 2MASS J17134806+6433581, the star is classified as an early K dwarf.
TOI-4600 hosts at least two giant exoplanets: TOI-4600b and TOI-4600c.
The inner planet, TOI-4600b, is 6.8 times larger than Earth, and has an orbital period of 83 days.
The outer planet, TOI-4600c, has a radius of 9.4 Earth radii and an orbital period of 483 days.
These two planets are likely gas giants, similar to Jupiter and Saturn, though the composition of the inner planet may be more of a mix of gas and ice.
Both planets bridge the gap between hot Jupiters and the much colder, longer-period gas giants in our Solar System.
“These longer-period systems are a comparatively unexplored range,” said Katharine Hesse, a technical staff member at MIT’s Kavli Institute for Astrophysics and Space Research.
“As we’re trying to see where our Solar System falls in comparison to the other systems we’ve found out there, we really need these more edge-case examples to better understand that comparison.”
“Because a lot of systems we have found don’t look anything like our Solar System.”
TOI-4600c has the longest period that TESS has detected to date. It is also one of the coldest, at about 191 K, while the inner planet is a more temperate 347 K.
The distance between the two planets, which is about the same as the space between Mercury and Mars, implies there could be other planets in the system.
“We want to see if there’s evidence for more planets,” said Dr. Ismael Mireles, an astronomer at the University of New Mexico.
“There’s definitely a lot of room for potential planets, either closer in, or further out.”
“And we show that TESS is capable of finding both warm and cold Jupiters.”
The discovery is descirbed in a paper in the Astrophysical Journal Letters.
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Ismael Mireles et al. 2023. TOI-4600 b and c: Two Long-period Giant Planets Orbiting an Early K Dwarf. ApJL 954, L15; doi: 10.3847/2041-8213/aceb69
