The Kitt Peak National Observatory Telescope helps determine that
” data-gt-translate-attributes=”[{” attribute=””>Jupiter-like Planet is the lowest-density gas giant ever detected around a red dwarf.
A gas giant
“Giant planets around red dwarf stars have always been considered difficult to form,” says Shubham Kanodia, a researcher at the Carnegie Institution for Science’s Earth and Planets Laboratory and first author of a paper published in The Astronomical ReviewI. “So far this has only been examined with small samples from Doppler surveys, which have generally found giant planets further away from these red dwarf stars. So far we haven’t had a sample large enough number of planets to find nearby gaseous planets robustly.
There are still unexplained mysteries surrounding TOI-3757 b, the biggest being how a gas giant planet can form around a red dwarf star, and especially one with such a low density. The Kanodia team, however, believe they have a solution to this mystery.
They propose that the extra-low density of TOI-3757 b could be the result of two factors. The first concerns the rocky core of the planet; Gas giants are thought to begin as massive rocky cores about ten times the mass of Earth, at which point they quickly pull together large amounts of nearby gas to form the gas giants we see today. TOI-3757b’s star has a lower abundance of heavy elements compared to other M dwarfs with gas giants, and this may have caused the rocky core to form more slowly, delaying the onset of gas accretion and thus affecting the overall density of the planet.
The second factor may be the orbit of the planet, which is tentatively considered to be slightly elliptical. There are times when it gets closer to its star than at other times, resulting in substantial excess heat that can cause the planet’s atmosphere to swell.
NASA’s Transiting Exoplanet Survey satellite (
” data-gt-translate-attributes=”[{” attribute=””>TESS) initially spotted the planet. Kanodia’s team then made follow-up observations using ground-based instruments, including NEID and NESSI (NN-EXPLORE Exoplanet Stellar Speckle Imager), both housed at the WIYN 3.5-meter Telescope; the Habitable-zone Planet Finder (HPF) on the Hobby-Eberly Telescope; and the Red Buttes Observatory (RBO) in Wyoming.
TESS surveyed the crossing of this planet TOI-3757 b in front of its star, which allowed astronomers to calculate the planet’s diameter to be about 150,000 kilometers (100,000 miles) or about just slightly larger than that of Jupiter. The planet finishes one complete orbit around its host star in just 3.5 days, 25 times less than the closest planet in our Solar System — Mercury — which takes about 88 days to do so.
The astronomers then used NEID and HPF to measure the star’s apparent motion along the line of sight, also known as its radial velocity. These measurements provided the planet’s mass, which was calculated to be about one-quarter that of Jupiter, or about 85 times the mass of the Earth. Knowing the size and the mass allowed Kanodia’s team to calculate TOI-3757 b’s average density as being 0.27 grams per cubic centimeter (about 17 grams per cubic feet), which would make it less than half the density of
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