Using NASA’s TESS Space Telescope, an international research team has identified twin planets with densities lower than cotton candy.
The research team, led by the University of Oxford, in collaboration with Université Côte d’Azur/Observatoire de la Côte d’Azur, and the University of Birmingham, detected the rare ‘super-puff’ giant planets orbiting an F7-type dwarf star that is about 1,110 light-years from Earth.
The planets, named TOI-791 b and TOI-791 c, are each about the size of Jupiter but are significantly less dense. Little is known about how ‘super-puff’ planets form, but this discovery could help fill in some gaps. The findings were published in Monthly Notices of the Royal Astronomical Society.
“Only a handful of these super-puffy planets are known, and it is even rarer to find two in the same system. Their extremely low densities make them fascinating targets for understanding how planetary systems form and evolve,” said lead author George Dransfield (she/her), from the University of Oxford and presenter for BBC Sky at Night, in a press release.
What We Know About TOI-791 b and TOI-791 c
(Image Credit: NASA/Daniel Rutter)
TOI-791 b and TOI-791 c are siblings, according to the study, and likely formed together from the same disc of dust and gas that surrounded their star, which is located in the southern constellation of Volans. Despite their size, TOI-791 b has a density of 0.038 grams per cubic centimeter, and TOI-791 c has a density of 0.047 grams per cubic centimeter. In comparison, Jupiter has a density of about 1.33 grams per cubic centimeter.
More surprising is that the densities are lower than that of cotton candy, which has a density of about 0.05 grams per cubic centimeter. Earth, on the other hand, has a density of about 5.5 grams per cubic centimeter.
Based on the team's observations, these planets are also in a rare gravitational relationship — known as a 5:3 mean-motion resonance. This means that for every five orbits the inner planet makes, the outer planet makes about three. This relationship results in the planets repeatedly tugging on one another, causing measurable shifts in their orbits.
Rarer still is the fact that only four other known systems contain two or more super-puff planets, making this system vital to understanding how these planets form.
Read More: JWST Spots a Nearby Super-Earth That Could Look Like the Moon or Mercury
How TOI-791 b and TOI-791 c Were Observed
Dr. George Dransfield and colleagues with the Antarctic Telescope, ASTEP
(Image Credit: Karim Agabi/IPEV/PNRA)
According to the study, volunteers participating in the Planet Hunters TESS citizen-science project identified TOI-791 b and TOI-791 c as candidate planets in 2019 and 2023. Researchers then analyzed data collected by the project to measure the planet’s size and density.
Researchers can tell the size of a planet by how much it dims its host star’s light when it passes in front of the star. The dim light helps reveal the planet's size. This is also how the team noticed that the sibling planets had a unique gravitational relationship. Researchers then measured the timing shifts of TOI-791 b and TOI-791 c to calculate their densities.
Researchers from multiple organizations have been observing these planets and gathering data on them for over eight years through various telescopes and observatories. The Antarctic Search for Transiting ExoPlanets (ASTEP) telescope at Concordia Station in Antarctica — which was jointly operated by Université Côte d’Azur/Observatoire de la Côte d’Azur and other international collaborators — offered the team optimal viewing thanks to long periods of darkness. The team even captured the planets’ long transits, which each last about 11 hours, in a one uninterrupted observation.
According to the study, these are the longest continuous planetary transits observed from the ground in their entirety.
What’s Next for TOI-791 b and TOI-791 c?
How these planets form is still a matter of debate. One leading explanation is that the planets have atmospheres rich in hydrogen and helium, which could account for a significant portion of their mass. The theory goes on to say that these giant planets could have formed farther from the host star, allowing cooler temperatures to rapidly draw in gases around a solid core.
“This system offers a unique laboratory for understanding how super-puff planets form and evolve. We propose to carry out space-based observations using the James Webb Space Telescope to assess if the puffy atmosphere contains carbon-, nitrogen-, and oxygen-bearing species, revealing new insight into how these unusual planets formed,” Amaury Triaud, a professor at the University of Birmingham and the U.K. Principal Investigator of ASTEP and co-author of the study, said in the press release.
Read More: JWST Peers Into the Haze Surrounding an Unusual Cotton Candy-Like Planet
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Monthly Notices of the Royal Astronomical Society: ASTEP confirmation of a pair of long-period Jupiter-sized planets with extremely low densities transiting TOI-791
