Wednesday, May 09, 2007

Hot Gas

Though the Griffith Park fire is still burning nearby, we will try to focus on hot gas elsewhere. Astronomers have discovered the hottest gas giant yet found. Object HD 149026b orbits a star 279 light-years away in the constellation Hercules. It orbits in just 2.877 Earth-days, with an estimated temperature of 2040 degrees Celsius! The planet is so hot that it would have to absorb all the radiation from its star. HD 149026b was detected transiting its star in 2005 by "amateur" astronomer Ron Bissinger with his 14-inch Celestron.

Many "hot Jupiters" have been found orbiting close to stars. Present theories of planet formation can not explain them, for at these temperatures they would quickly boil away. If these planets formed around singularities, a Black Hole's gravity would keep them in one piece. Radiation from an internal singularity would also explain why HD 149026b is so hot.

Meanwhile, our Cassini spacecraft has discovered that Saturn's jet streams are driven by rotating eddies. Previously the reverse was assumed, that jet streams affected the eddies. These rotating stormlike features originate deep within Saturn's atmosphere, powered by unknown forces. Saturn and other gas giants give off far more energy than they receive from the Sun. This energy rises to the surface in storms and vortices, like those that would be produced by a Black Hole. There is more inside the planets than meets the eye.

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Blogger Mitchell said...

"If these planets formed around singularities, a Black Hole's gravity would keep them in one piece."

Why does that help? From a gravitational perspective, whether or not there is a central singularity is just a hypothesis about the distribution of internal mass. By the time you get to the atmospheric surface - which is where the boiling away happens - Gauss's law should make those details irrelevant.

There is a nice little Hawking radiation calculator here - you can set temperature, units, etc., and other black-hole properties are adjusted accordingly.

11:01 PM  
Blogger L. Riofrio said...

Thank you for the interesting link. As you say, even if a tiny Black Hole were inside the Earth, Gauss insures that we might not notice. Singularities become impirtant in the initial formation. Particles of dust will not accrete unless they have the mass of mountains.

6:11 AM  
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9:14 AM  
Blogger CarlBrannen said...

The MOND observations suggest that gravitation needs to be adjusted for very small accelerations. The adjustment is to increase the acceleration.

If this applies as well to small masses (or black holes) as it does to galaxies, then they probably accrete matter a whole lot better than expected.

Finally, to get attracted matter to absorb into a body it would really help if the equations of motion were dissipative. That is, they should have an effect that turns velocity into heat. Normal matter has to do this by chaos, a black hole can do it by Hawking radiation.

If gravitation has to be redone to get MOND, then who knows what it will do at small distances. Perhaps the dissipative region of a small black hole is far larger than three times the event horizon radius. (Hope this wasn't too long.)

7:40 PM  
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