PSR B1257+12 D: extrasolar dwarf planet?

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Should this planet (if confirmed) be clasified as an "extrasolar dwarf planet"?

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PSR B1257+12 D: extrasolar dwarf planet?

Post by NuclearVacuum on 18th September 2008, 12:21 pm

Now that the Solar system contains five dwarf planets, I would like to bring up an opinion poll on PSR B1257+12 D. Because of its mass and presumable size, should this planet be classified as the first "extrasolar dwarf planet"? I do mean should we use this definition if the planet is confirmed. alien
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Re: PSR B1257+12 D: extrasolar dwarf planet?

Post by Lazarus on 18th September 2008, 1:14 pm

I'd say yes. According to the estimator in this paper, this object would not clear its orbital neighbourhood within a Hubble time. The calculation basically boils down to

Λ≈1.7×1016(Mp/M)2a-3/2

for a solar mass star. Planets (in their terminology, überplanets) have Λ>1, dwarf planets (in their terminology, unterplanets) have Λ<1. I'm not entirely sure how to translate this to other stellar masses, but it seems there is an additional scaling of Ms1/2, which would mean

Λ≈1.7×1016(Ms/M)(Mp/Ms)2a-3/2

For the outer object orbiting PSR B1257+12, this works out as Λ<1, so it looks like it is not a planet. The remaining question is whether it is in hydrostatic equilibrium - if the true mass is high enough, then yes, make it a dwarf planet.
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Re: PSR B1257+12 D: extrasolar dwarf planet?

Post by Darkness nova on 1st October 2008, 4:11 pm

I dunno.

Has it cleared out it's orbital path?

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Re: PSR B1257+12 D: extrasolar dwarf planet?

Post by AVBursch on 15th May 2009, 7:56 pm

If a dwarf planet can be viewed as a world that has planet-like characteristics, but does not have sufficient mass to be a full-fledged planet, then the outermost known world of PSR B1257+12 would be a dwarf planet. The world has 21% of the mass of Pluto -- that's definitely well within the mass range for a dwarf planet.

As for clearing it's orbital neighborhood -- not likely. The pulsar has 1.4 (presumed) times the mass of the Sun, and the world has a semi-major axis almost three times that of Earth. At a distance of 2.8 AU from the pulsar, a world would likely need to have at least 5 times the mass of Pluto in order to establish dynamical dominance.

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