Odd Planet Confuses Scientists

eldavojohn writes "While there's been a lot of debate about what is a planet, there is a recent discovery that has scientists even more confused. COROT (COnvection ROtation and planetary Transits) spotted an object that appears to be the size of Jupiter yet is 21.6 times more massive ... and orbits its star in a mere four days and six hours. Now, the other piece of the puzzle is that the star it orbits is more massive and only slightly larger than our Sun. But they can't describe this thing orbiting it. So far they think it is more likely to be a 'failed star' but have settled with 'member of a new-found family of very massive planets that encircle stars more massive than the sun' to describe it accurately."

Comments

That's no planet.

[MRe_nl]

"the size of Jupiter yet 21.6 times more massive.. and orbits its star in a mere four days and six hours."

That's New Year roughly twice a week, by Jove.
Party on ; ).

Bad Data

[SpaceMika]

This was followed up on the astro mailing lists as faulty data -- the observers mistook sunspot-dimming for a planet passing in front of the star. The correction hasn't made it to journalists yet and the science article is still in draft, so no link-to-reference, sorry! Planetary formation theory is fragmented and deeply in need of reworking (anyone want a phd topic?), but not to incorporate Jupiters in Mercury-orbits (yet).

Re:I hate to say it..

[RuBLed]

You're so dense.

Detecting Exoplanets

[SpaceMika]

There are two ways of detecting exoplanets:
1. Wobbles -- what you explained: watch a star for deviations in its orbit by observing tiny redshifts and blueshifts. Our own sun does a little jiggle thanks mostly to Jupiter.
2. Dimness -- what they did for this object. Watch a star for dimming as something passes in front of it, although you have to be careful of other causes of temporary decreases in luminescence (like sunspots).

In both cases, it really needs repeated observations over time to establish that it's an orbital event and not something random. In the good ol' days of exoplanet discovery when the equipment wasn't so hot & we expected to find planets pretty much like ours, it took a whole lot of observations before anyone was willing to take the risk of announcing a discovery. Now, with better equipment making it easier to detect hiccups in a star's routine and a more open attitude about how planets behave, discoveries are being announced a lot earlier in the observation process.

To be fair, TFA does give itself a whole lot of wiggle room in interpreting the data. It just fails to mention that follow-up observations aren't confirming the orbital parameters of the assumed planet.

Don't think so

[Moraelin]

Actually, I don't think that metallic hydrogen is twice as dense as solid lead.

If you look at most metals, the higher the atomic weight, the higher the density of the solid. Depleted uranium is heavy, while Aluminium is lightweight, and Lithium is half the density of water, for example. So for hydrogen, metallic or not, to be denser than lead, you need it to be packed tighter than, I think, is physically possible.

At some quick maths, a hydrogen atom is 1, lead is 207-208 (82 protons and a load of neutrons.) I know that some mass is actually in the binding energy between those, but for some quick and very approximative maths let's say a lead atom is 200 times heavier than a hydrogen one. (Plus/minus something.) At the same distance between atoms, lead will be 200 times heavier than hydrogen. To go for twice as heavy, you need the hydrogen atoms to be packed at over 7 times less distance from each other than lead atoms are.

At a quick googling, the estimated range of densities for metallic hydrogen is anywhere between 0.4g per cubic centimetre (less than lithium) and 4g per cc (4 times as heavy as water), with apparently 0.8 being the most likely candidate for where it turns metal. Compress it any denser and it'll start to fuse. And we're still nowhere near as heavy as we need for that planet.

What throws a further spanner into it, is that our own gas giants _already_ have a core of metallic hydrogen. That' what's in the middle of Jupiter and Saturn. So something 26 times heavier, hmm, must be something else.