Two ‘super-puff’ planets are as wispy as cotton candy
Article excerpt
TOI-791 b and TOI-791 c are about the size of Jupiter, but 28, 35 times less dense. The post Two ‘super-puff’ planets are as wispy as cotton candy appeared first on Popular Science.
A pair of sibling gas giants originally spotted by citizen scientists are so lightweight that their density resembles wispy cotton candy more than a standard atmosphere. The rare duo detailed today in the journal Monthly Notices of the Royal Astronomical Society even have an appropriate technical term to describe them. TOI-791 b and TOI-791 c fit the bill for “super-puff” planets.
“Only a handful of these super-puffy planets are known, and it is even rarer to find two in the same system,” George Dransfield, a study co-author and University of Oxford astrophysicist said in a statement. “Their extremely low densities make them fascinating targets for understanding how planetary systems form and evolve.”
The two planets are situated about 1,110 light-years from Earth, in the southern constellation of Volans.TOI-791 b has a density of 0.022 and TOI-791 c has a density of 0.027 ounces per cubic inch. To put those numbers in perspective, Earth possesses a density of 3.18 ounces per cubic inch, while Jupiter (our solar system’s largest planet) exhibits an average of 0.76 ounces per cubic inch. And while both of these puff planets are roughly the same size as Jupiter, they are about 28 to 35 times denser. For a more tangible, tastier frame of reference, the spun sugar used in cotton candy has a density of about 0.29 ounces per cubic inch.
Comparison of the exoplanets in the TOI-791 system with planets in our solar system. Image: NASA / Daniel Rutter
TOI-791 b and TOI-791 c were flagged as candidate planets about four years apart by volunteers combing through data collected by NASA’s Transiting Exoplanet Survey Satellite (TESS), as part of the Planet Hunters TESS citizen-scientist project. For eight years, astronomers around the world combined efforts to study the two objects, using observatories including the exoplanet telescope at Concordia Station in Antarctica.
Researchers examined each planet’s transit in front of its host star to measure how much they dimmed the stellar light. These tiny calculations then helped the team estimate their size, mass, and other properties. Only four other systems are known to include super-puff planets, but the team discovered details that make the latest additions even more unique. TOI-791 b and TOI-791 c are united by what’s known as a 5:3 mean-motion resonance, a seldomly seen gravitational relationship that makes the inner planet orbit five times for every three orbits of the outer planet.
Dr. George Dransfield and colleagues with the Antarctic telescope, ASTEP (Antarctic Search for Transiting ExoPlanets), during a summer service mission in 2021/2022. Image: Karim Agabi / IPEV / PNRA
“These multi-planetary systems are complex, with gravitational interactions between the planets that evolve over very long periods, tens of years or more,” added study co-author and astronomer Tristan Guillot.
Astronomers still aren’t quite sure how super-puff planets came into existence. One prominent theory hypothesizes they contain huge atmospheres rich in hydrogen and helium that formed while the planets orbited far from their host star inside colder areas of a protoplanetary disc. Going forward, the researchers plan to continue studying TOI-791 b and TOI-791 c to gain a better understanding of super-puff planets, including potentially enlisting the powerful James Webb Space Telescope.
The post Two ‘super-puff’ planets are as wispy as cotton candy appeared first on Popular Science.