Updated

Updated · CBS New York · Jun 25

Astronomers Find 2 Jupiter-Sized Super-Puffs 1,110 Light-Years Away, the Lightest Known

Updated

Updated · CBS New York · Jun 25

Astronomers Find 2 Jupiter-Sized Super-Puffs 1,110 Light-Years Away, the Lightest Known

Q: How can planets the size of Jupiter be lighter than cotton candy?

They can be Jupiter-sized yet “lighter than cotton candy” because size and density are not the same thing. These newly found worlds are enormous in volume but contain relatively little mass, so their average density is extraordinarily low. Astronomers classify them as rare “super-puff” exoplanets. Although they are about the size of Jupiter, they are made mostly of hydrogen and helium, the lightest elements, in very swollen, diffuse atmospheres. That means a huge amount of space is filled with very little material. Their densities are about 0.038 and 0.047 grams per cubic centimeter, compared with roughly 0.05 g/cm³ for cotton candy and 1.33 g/cm³ for Jupiter. In other words, Jupiter is roughly 28 to 35 times denser. This does not mean the planets weigh less than a bag of cotton candy overall. It means that, cubic centimeter for cubic centimeter, their material is less dense on average. A planet can still be large and massive, but if its gas envelope is extremely expanded, its density can remain exceptionally low. Researchers think such planets likely formed in gas-rich disks around young stars, probably farther from their star where gas could accumulate into a thick envelope. Over time, some may lose material, but these two still appear unusually inflated. Because fewer than 40 super-puffs are confirmed among more than 6,000 known exoplanets, they are valuable for testing theories of how planets form and evolve.

3 articles · Updated · CBS New York · Jun 25

Two Jupiter-sized exoplanets orbiting a star 1,110 light-years away have emerged as the lightest known of their size, with densities lower than cotton candy and closer to shaving foam, researchers reported Wednesday.
NASA's TESS first detected the worlds, and Earth-based telescopes pinned down their masses and densities; one completes an orbit in 139 days and the other in 232 days.
TOI-791 b and c are thought to be mostly hydrogen and helium, but Webb Space Telescope follow-up will be needed to confirm their atmospheres and explain how such bloated planets survived.
Fewer than 40 super-puffs are known among nearly 6,300 confirmed exoplanets, making the pair a rare test case for theories of giant-planet formation and evolution.