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Ilya
2005-Feb-08, 05:14 AM
http://www.space.com/scienceastronomy/miniature_solarsys_050207.html

It orbits PSR B1257+12, the same neutron star which had very first confirmed extrasolar planets, back in 1991. I knew that pulsar planets are by far easiest to detect -- the innermost planet of PSR B1257+12 is only the mass of Moon, -- but this? The latest body is about twice the mass of Ceres!


"Because our observations practically rule out a possible presence of an even more distant, massive planet or planets around the pulsar, it is quite possible that the tiny fourth planet is the largest member of a cloud of interplanetary debris at the outer edge of the pulsar's planetary system," said Penn State researcher Alex Wolszczan, who since 1990 has led the investigation into the system.

Brady Yoon
2005-Feb-08, 05:28 AM
Cool stuff! :) Technology has advanced so much!

I don't think an asteroid twice the mass of Ceres is that rare. There are KBO's and Sedna which mass around there, and the asteroid belt is very old. Collisions between asteroids and into planets have thinned out the asteroid belt to a fraction of it's old size. Perhaps there were huge asteroids considerably larger than Ceres billions of years ago.

Padawan
2005-Feb-08, 08:24 AM
Thanks for sharing the article =)

Grand Vizier
2005-Feb-08, 08:41 AM
From the article:


At the other end of the life cycle for stars and planets, NASA's Spitzer Space Telescope has spotted a disk of potential planet-making material around a young brown dwarf. (my itals)

I'm wondering what criteria we have for deciding the age of a brown dwarf. I guess if it's still burning deuterium, maybe. The question is relevant, I think, because if it turned out not to be young, then we don't necessarily know that such a disk would ever form planets. (Which would be a pity...)

TriangleMan
2005-Feb-08, 12:00 PM
For some reason I thought neutron stars needed mass in excess of 15J ?

Ilya
2005-Feb-08, 04:14 PM
From the article:


At the other end of the life cycle for stars and planets, NASA's Spitzer Space Telescope has spotted a disk of potential planet-making material around a young brown dwarf. (my itals)

I'm wondering what criteria we have for deciding the age of a brown dwarf.

Temperature. The older a brown dwarf is, the cooler it is.

TriangleMan:

The article is about two different systems. One has a neutron star in its center. The other has a very low mass (15J) brown dwarf.

Kaptain K
2005-Feb-08, 10:19 PM
I don't think an asteroid twice the mass of Ceres is that rare.
I think you are missing the point of the article. It's not that they are rare. It's that we found one. 15 years ago, we hadn't found a single extra-solar planet. Now, we are finding extra-solar asteroids.

Kullat Nunu
2005-Feb-08, 10:56 PM
I think you are missing the point of the article. It's not that they are rare. It's that we found one. 15 years ago, we hadn't found a single extra-solar planet. Now, we are finding extra-solar asteroids.

Planets around pulsars are probably very rare. No other neutron star has been found to have any planets despite the extreme accuracy of the pulsar timings. PSR B1620-26 c doesn't count, because that planet probably didn't form around the pulsar.

jami cat
2005-Feb-09, 05:16 AM
...The older a brown dwarf is, the cooler it is...


Old brown dwarfs "are" pretty cool. :)
Old Brown Dwarfs (http://www.antropoide.blogger.com.br/oompa%20loompa2.jpg)

iron4
2005-Feb-10, 05:29 PM
Hum,
how come can exist planets orbiting around a pulsar? A pulsar is a neutron star, so it can only be formed as a consequence of a supernova. I suppose that if there were planets around the star these planets were destroyed in the supernova explosion, or expulsed to the ISM. is possible that these planets around the pulsar were orbiting the star, and somehow survived to the supernova explosion? Or did they formed after the supernova explosion, as an aggregation of material left after the explosion?

Doodler
2005-Feb-10, 05:35 PM
Hum,
how come can exist planets orbiting around a pulsar? A pulsar is a neutron star, so it can only be formed as a consequence of a supernova. I suppose that if there were planets around the star these planets were destroyed in the supernova explosion, or expulsed to the ISM. is possible that these planets around the pulsar were orbiting the star, and somehow survived to the supernova explosion? Or did they formed after the supernova explosion, as an aggregation of material left after the explosion?

The current party line is coalescence after the supernova, subject to revision of course. There's also the possibility of them being remnants of the existing planets, but that seems unlikely to me. Given that the stars that create these systems were probably huge, some of those planets would have been inside the star before the boom.