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Science

Hungry Millisecond Pulsar Found Feeding 15

Posted by michael
from the yum-yum dept.
Gopher971 writes: "The latest joint discovery by the Hubble Telescope is a Millisecond Pulsar feeding off of it's companion Red Giant star. Scientists have long speculated on how Milli Pulsars formed and now have proof to back up their claims. See the UniSci link and The Irish Times link."
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Hungry Millisecond Pulsar Found Feeding

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  • is that... no.... (Score:2, Interesting)

    by elroyjenkins (221758)
    A link [ireland.com] to an artists representation of the process...


    tee hee... tell me that "object" in the middle isnt a sperm, geez...
    did disney make the pic or something?
  • Hmmm, blackhole (Score:2, Interesting)

    by Gyl (318790)
    So, does anybody out there know enough about astrophysics to know how close this thing would be to becoming a black hole? THAT would be a cool process to watch. Basically, the question is, how massive is the pulsar, and how much stuff is it sucking up from the companion star?
    • Two theories (Score:5, Interesting)

      by marcus (1916) on Friday February 22, 2002 @11:34AM (#3051384) Journal
      I'm not really up-to-date, but...

      Both say that the material will pile up on the surface until it reaches fusion temperatures and then start to burn.

      One says that the burn will be fast and explosive, blowing all the rest of the new, degenerate and normal matter off of the surface. An extension of this idea suggests that the explosion, since it is very unlikely to be symmetrical and simultaneous all over the surface of the neutron star, will disrupt and break up the neutron star itself. We are talking about a big, nova or supernova class explosion here.

      The other says that the fusion burn will be slow, intermittent or periodic, something more like a continuous series of neutron star sized burps and blow stuff off here and there and simply heat things up. The heat and radiation from the explosions slows the infall of matter, a form of negative feedback, so that the process is self throttling. Somewhere along the way, it might accumulate enough to collapse, otherwise the process just continues until the donor star "runs out of gas" and then everything calms down.

      There are nuances to both depending on the rate of deposition, spin, size of the original neutron star, etc.

      Mostly there's just not enough data to tell, perhaps both happen depending on the situation.
      • One says that the burn will be fast and explosive, blowing all the rest of the new, degenerate and normal matter off of the surface.
        Where'd that theory come from? I've been reading about neutron stars for some time and I've seen this as an explanation for X-ray bursters (the ignition of the accumulated hydrogen makes the surface extremely hot for a while, then it cools), but the star does not lose matter; the energy of fusing hydrogen is not sufficient to overcome the gravity of a neutron star.

        That sounds more like a certain theory for the collapse of white dwarfs under infalling matter. Supposedly this would always happen at the same mass and produce uniformly bright supernovae.

        • IIRC this was proposed to explain 2 things. One was the discovery of "wandering", lone yet apparently young(aged by spin) NSs that are found without a surrounding nebulous SN remnant. The asymmetry of the primary(NS producing) or the secondary(after eating a neighbor) explosion would have propelled the NS away from the site of the explosion.

          The other thing to be explained was the discovery of SN remnants that have no detectable NS at or near the center.

          Obviously, both could be covered by the propelled version, but no one knows, AFAIK. Perhaps it was proposed simply as an attempt to cover all bases. If the NS is not there, it must have moved or been destroyed. OTOH, if the NS is here, and there is no nebulous remnant nearby, and there is no idea of how to destroy the remnant, then the NS must have moved.

          If there has been more data gathered, better theories produced or simply better analysis of existing data and theory that has ruled out one of these options, that's fine by me. It has been a while since I studied or paid attention to this stuff.

        • FYI that certain "same mass" is the Chandrasekhar limit, which is 1.4 solar masses. This type of supernova (type Ia) is invaluable for determining distances in deep space for exactly the reason you mentioned (they always blow with the same mass).
    • So, does anybody out there know enough about astrophysics to know how close this thing would be to becoming a black hole?
      Nothing in the article hinted at that.
      THAT would be a cool process to watch.
      ... from a safe distance of several light-years (mind the neutrinos, they don't care about shielding).

      This pulsar is in a globular cluster, which probably contains a number of other neutron stars already. Sooner or later two of them are going to make close passes and get captured into a mutual orbit, which will then decay. When the two neutron stars merge they will likely collapse catastrophically into a black hole, with the added excitement of kilohertz gravitational waves thrown in.

      • ... from a safe distance of several light-years (mind the neutrinos, they don't care about shielding).

        For the same reason they don't care about shielding, they don't care about you, either.

        And I'm still waiting for those gravitational waves to get observed. It would be so danmed cool to listen to the creation of a black hole that way...

        • A supernova in the solar system would kill anyone out to Jupiter just with the neutrinos. (Of course, if you survived that, your problems are just begining!) They interact very weakly with other matter, but when ya gets that many of the buggers...
          • (Of course, if you survived that, your problems are just begining!)

            Exactly. If you're close enough for the neutrinos to have any macroscopic effect, you're gonna be nothing but ionized H, O, N, C, etc. real soon (well, maybe in a few hours. The electromagnetic radiation can take a long time to reach the surface of a supernova, while the neutrinos get there at about the velocity of light). But the earlier poster warned about neutrinos after mentioning observing from a few light-years away, where the flux would be *far* too low to worry about.

    • how close this thing would be to becoming a black hole?

      Not very, I would guess. Neutron stars tend to have masses just at or near the Chandrasaker limit (actually, sometimes a bit lower, even). That's 1.4 solar masses. A neutron star becomes a black hole at between 2 and 3 solar masses (number uncertain). So that's a fair margin, particularly if you take the 3 solar mass limit.

      Now, how much matter is transfered? If the neutron star is 1.4 solar masses, if it is typical size (10 km radius) and if the companion is 1 AU from the neutron star, you'd have to transfer about 2.5 X 10-5 solar masses to make a millsecond pulsar, I'm figuring. That's a tiny amount. The mass tranfer required goes like 1/r2 (until the mass transfered is a large fraction of the pulsar's inital mass, anyway). So even at 0.1 AU, it's still only 1/1000 of a solar mass. (0.1 AU = 10 solar radii, roughly) They'd almost have to be in physical contact to require enough mass transfer to push the neutron star over the black hole limit.

  • Globular Clusters! (Score:2, Informative)

    by s0l0m0n (224000)
    Sounds like a sick snack, don't it.

    here's a link to Globular Cluster NGC6397 [seds.org]

    Can you find the pulsar? *grin*

    Photo taken from the Hubble, circa 1994.

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