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posted by martyb on Sunday October 16 2016, @06:30AM   Printer-friendly
from the for-some-sizes-of-bathtub dept.

Gas giants that are closer to their host stars or orbiting brighter ones become inflated, decreasing their density:

Hot Jupiters – gas giant exoplanets that orbit scorchingly close to their stars – are inexplicably puffy. "We see these planets that are the sizes of stars without being anywhere near the mass of those stars," says Sam Grunblatt at the University of Hawaii. HAT-P-1b, for example, contains half the mass of Jupiter yet is 20 per cent larger in radius. This gives it such a low density that it would float in a bathtub.

[...] To search for such systems, Grunblatt and his colleagues examined data from the Kepler space telescope. They discovered that one planet, dubbed EPIC 211351816.01, is 1.3 times Jupiter's size and far enough away from the red giant that it could only have inflated after the star had swelled outward. "We're catching it in a phase where its radius is being expanded because the star's brightness is increasing a lot, just in the past few hundred million years," says Jonathan Fortney at the University of California, Santa Cruz.

Adam Burrows at Princeton University says we can't reach strong conclusions from studying just one object. But he says that another recent study shows that older planets, which orbit brighter stars, tend to be slightly larger than younger planets, which orbit fainter stars. Taken together, both studies strongly suggest that stellar radiation alone can inflate planets, he says.

Some moons of Jupiter and Saturn will not survive the Sun's transformation into a red giant.

EPIC 211351816.01: A (Re-?)Inflated Planet Orbiting a Red Giant Star

See Wikipedia for background information on Hot Jupiters.


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  • (Score: 0) by Anonymous Coward on Sunday October 16 2016, @03:30PM

    by Anonymous Coward on Sunday October 16 2016, @03:30PM (#414870)

    such a low density that it would float in a bathtub.

    So is saturn. https://en.m.wikipedia.org/wiki/Saturn [wikipedia.org]