Astroboffins score a first by spotting traces of helium on an exoplanet Astronomers have detected helium floating around in the atmosphere of an exoplanet for the first time, according to a paper published in Nature on Wednesday. The discovery was made after a team of scientists probed WASP-107b with the Hubble Space Telescope. It's an exoplanet located about 200 light-years away from Earth that …
Doesn't this mean that the crust of the planet contains a large amount of radioactive isotopes? As I understand it all of the naturally occurring helium on earth originates from radioactive sources through alpha decay. Perhaps they have natural reactors under the surface like Oklo used to have?
"...the crust of the planet..."
It's unlikely to have a crust, at least in the sense I suspect you mean; with a mass of ~1/8th that of Jupiter's, and if its density is only 0.19 g/cc, it's far less dense than water and even less dense than Saturn (~0.68 g/cc).
In fact, as planets go, it must be amongst the most tenuous, and certainly unlike any of the planets in our solar system.
No, that's because Earth lost its primordial helium - it all escaped because it's too light to hold on to. We only have hydrogen because it formed compounds such as water, while helium does not form compounds.
As the article says, helium is the second most abundant element after hydrogen. About a quarter of total mass. That nearly all formed at the time of the big bang.
Astrophysicists treat the universe as consisting of hydrogen, helium, and 'metals' - everything else, a slight impurity.
In your theory were correct then Jupiter (10% helium, by volume) would have one hell of a radioactive crust.
It's true, most of earth's helium is radiogenic. But that's because we didn't have much to start with and we're too light to hang on to what we had. (Remember helium is pretty inert and doesn't get tied up in chemical compounds.) This planet is a gas giant, about 40 times the mass of earth, and would have no trouble hanging on to its helium, if it didn't have its face rubbing in the star. (Mercury: semimajor axis ~0.4AU; WASP-107b: semimajor axis: 0.06AU)
I'm not surprised that it was so difficult to see helium atoms on an exoplanet.
I mean the thing about an exoplanet, it's main distinguishing feature, is it's far far away, outside of our system. In a telescope it's really teeny tiny. And the thing about a helium atom, the size of a helium atom, your basic atomic size, is that it's really quite small!
So how're you supposed to see 'em?
(And don't even get me started on black holes.)
Well sure, but you know telescopes, right? Their main distinguishing feature is that they *extend* - if boffins had a problem spotting those atoms, they clearly just weren't using a long enough one to get a view from up close...
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