The Fluffy Planets of TOI-791
Astronomers have recently made a groundbreaking discovery regarding two planets orbiting the star TOI-791, located approximately 1,100 light-years away. These planets, comparable in size to Jupiter, possess a density lighter than cotton candy—around 0.04 grams per cubic centimeter. This astonishing finding, published in the “Monthly Notices of the Royal Astronomical Society,” offers new insights into planetary formation and development.
A Rare Discovery
The uniqueness of such super-fluffy planets cannot be overstated. “We only know a handful of such fluffy planets,” explains lead author Georgina Dransfield from the University of Oxford. Discovering two of them in a single system is exceptionally rare. Their remarkably low density makes them intriguing subjects for understanding the evolution of planetary systems.
The presence of these planets was first detected by amateur astronomers who explored the archive data of the Transiting Exoplanet Survey Satellite (TESS). This satellite monitors the brightness of millions of stars to find planets. When a planet transits in front of its star, it slightly dims the star’s light, offering a clue to its existence.
Understanding Their Density
To gauge the size of TOI-791’s planets, researchers analyzed how much the star’s light dims during transits. They found that although the two planets are similar in size to Jupiter, they possess only about one-thirtieth of Jupiter’s mass. This was surprising; the result points to an average density even lighter than cotton candy, commonly characterized at around 0.05 grams per cubic centimeter. For comparison, Earth has an average density of 5.5 grams per cubic centimeter, while Jupiter’s is about 1.3 grams.
Theories Behind Low Density
Many astronomers, including Dransfield and her colleagues, propose that these planets do not actually possess a cotton candy-like structure. Instead, it’s likely that the very size of these planets masks their true density. The hypothesis suggests that they contain a relatively small rocky core surrounded by a massive atmosphere composed primarily of hydrogen and helium. This extensive atmosphere could be absorbing and masking the starlight during transits, creating a misleading impression of size and density.
Alternatively, they may be enveloped in colossal dust clouds that might form following asteroid collisions, further altering their apparent size. Such peculiar planets might well arise in cool, dust-free regions around young stars—an idea supported by computer simulations.
Future Investigations with James Webb
The research team plans to utilize the James Webb Space Telescope to examine the peculiar atmospheres of these fluffy planets more closely. With its superior resolution, the James Webb telescope could provide critical insights that might unravel the enigma surrounding their low density and further enhance our understanding of planetary formation.
In summary, the planets orbiting TOI-791 represent a fascinating category of celestial bodies that challenge our current understanding. As we collect more data, we edge closer to solving the mystery of how these extraordinary planets came into existence and evolved.
