A Planet Swallowed Whole
by Sid Perkins
The notion of stars consuming their inner planets as they balloon during old age is firmly grounded in theory, but now scientists may have in hand the first evidence for such cannibalism. A star dubbed BD+48 740, an aging red giant in the constellation Perseus, is about 1.5 times the mass of our sun but has about 11 times the radius—a size that puts the star’s surface only one-sixth of the distance to Mercury’s orbit in our solar system but almost certainly bloated enough to have swallowed a close-orbiting “hot Jupiter” (early stages depicted in artist’s representation above).
Spectra show that BD+48 740 contains an abnormally high amount of lithium for a star its age, the researchers report online in The Astrophysical Journal Letters. That lithium, which is normally consumed in stars, was probably formed when the star heated up as it engulfed the doomed planet, the researchers say. Also, the team’s analyses suggest that at least one other planet has thus far survived the lithium-rich star’s growing pains—a massive orb about 1.6 times the mass of Jupiter, which circles the red dwarf in a highly-elongated orbit once every 771 days. The unusually large eccentricity of that orbit, the highest yet measured for an exoplanet, is yet another clue that BD+48 740’s planetary system has suffered major disruptions, the researchers contend.
(via: Science NOW) (image: NASA)