New Ultradense Planet Found; Astronomers Baffled

[n2doc]

Rachel Kaufman
for National Geographic News
Published February 22, 2012

A newly discovered planet 4,000 light-years away is just too dense.

Dubbed CoRoT-20b, the planet is thought to be a gas giant about four-fifths the size of Jupiter and orbits close to a sunlike star.

Despite the new planet's relatively diminutive size, this world has four times Jupiter's mass, making CoRoT-20b one of the densest known planets, a new study says.

That poses a problem for astronomers: If CoRoT-20b is structured like a traditional gas giant, with a solid core surrounded by a gassy atmosphere, the planet's core would have to make up 50 to 77 percent of the world's total mass.

By contrast, Jupiter's core is thought to represent just 15 percent of that planet's mass.

To have such a robust core, CoRoT-20b would defy current theories for how planets form.

more

http://news.nationalgeographic.com/news/2012/02/120222-new-planet-found-densest-jupiter-corot-space-science/

[Xipe Totec]

1. Sarah Palin, phone home... nt

[Ian David]

2. Dyson Sphere? n/t

[eppur_se_muova]

3. Are hollow ... so very low density. ;) nt

[Scootaloo]

4. Also, extremely huge

Yet probably undetectable by our current methods, since we rely on energy output from stars to guide us - and the dyson sphere capture almost all of it (...in theory)

[Ian David]

6. I'm wondering if our current methods for detecting exoplanets might mistake...

... a large hollow planet for a small dense one.

Obviously not if they're detecting the transit.

[Ian David]

5. The math is way beyond me, but I found this...

<snip>

The force on a statite would be F = L/(4 pi c r^2) - GMm/r^2, where L is the total luminosity of the sun (3.9e26 W), M is the mass of the sun, m is the density of the statite, r the distance to the sun and c is the speed of light. To remain in balance, the statite will have to have the density

m=E/(4 pi c G M)

(this assumes a 100% reflective statite). Note that this is independent of distance to the sun, closer to the sun the gravitational pull is greater, but the radiation pressure is stronger. The density depends only on the mass/luminosity of the sun. For a statite in the solar system, the density would be around 0.78 g/m^2

More:
http://www.aleph.se/Nada/dysonFAQ.html

I don't know whether that would make a Dyson Sphere more or less dense than something like the strangely dense planet.

[eppur_se_muova]

7. Density in this situation is calc'd same as for a solid sphere ...

that is, mass (measurements involving celestial mechanics treat this as a point mass) per unit volume, with the *empty* volume of the hollow sphere included. So any hollow object is going to have a low overall density. It might be made of very dense material, but there's no way to know that without more info than orbital characteristics. A space probe orbiting a hollow planet/Dyson sphere would spot something wrong right away (orbit too big for a given velocity); one orbiting a dense planet, likewise (orbit too small). But in either case it would be the overall density that would be most apparent, assuming at least approximately spherical symmetry.

A Dyson sphere would be mechanically supported (think a huge geodesic dome) so not dependent on photon pressure for support, unlike a statite.

[NRaleighLiberal]

8. Composed entirely of Santorium....

[jeff47]

9. What if it was a really, really huge gas giant that had its outer layers blown off

Being close to a star, perhaps it's losing it's atmosphere to solar wind?

[Motown_Johnny]

10. There was a time when people thought Jupiter would have a diamond core

I'm just saying....

[HopeHoops]

11. Shit happens. That explains just about everything.