4 ms·

I was hoping I could find something natural that spun faster, and thought that neutron stars might just be a candidate. Nope, not even close: " The star rotate

by jlgreco 13y ago

I was hoping I could find something natural that spun faster, and thought that neutron stars might just be a candidate. Nope, not even close: " The star rotates 716 times per second - faster than some theories predict is possible" http://www.newscientist.com/article/dn8576-fastspinning-neutron-star-smashes-speed-limit.html#.Uh5A03eBW2k http://www.newscientist.com/article/dn8576-fastspinning-neut...

jlarocco 13y ago
Apparently some dust particles in space spin up to 10 billion times a second: http://news.nationalgeographic.com/news/2011/01/110111-fastest-dust-spinning-universe-planck-microwave-science-space/ http://news.nationalgeographic.com/news/2011/01/110111-faste... No idea how they came up with that, though.
- OnACoffeeBreak 13y ago
  This article claims that spin rate is directly proportional to radio frequency emitted by the dust: http://www.economist.com/node/863276 http://www.economist.com/node/863276 > What is impressive is the rate at which the particles spin. It has to be equal to the frequency of the radio wave that is emitted, so Dr Finkbeiner's observations imply that many of the dust particles are rotating at ten billion revolutions per second.
ctdonath 13y ago
Surface of that moves about 18% of light speed, closer to what I was hoping to find. ETA: That's assuming a 12km radius, per Wikipedia.
- jlgreco 13y ago
  Yeah, only possible I imagine because the extreme gravitational forces, having already overcome electron degeneracy pressure, can hold it together when spinning at those speeds. My thinking is that this would allow you to get a neutron star spinning much faster, and, but a neutron star just retains angular momentum from the parent star which apparently doesn't get something that large spinning all that fast.
  - mtdewcmu 13y ago
    18% of the speed of light at the surface means that it could only spin slightly more than 5x faster without violating known physics. That isn't fast enough? If you want an in depth breakdown of this scenario, try posting a question at physicsforums.com. Be advised to follow their rules, though. Personal theories by non-physicists are severely punished (I made this mistake once).
Groxx 13y ago
Well, in some ways that is faster. Even if it's only 100m across (I assume it's larger than this), it spins at 223km/s at the surface. It would hit light speed at only 133km across (assuming I plugged those numbers correctly), so it must be smaller than that, which is a pretty small star.
- jlgreco 13y ago
  Neutron stars are bounded by mass, somewhere in the neighborhood of 3 solar units it seems (if it were more massive it would collapse further), so I think their radius is bounded too (since if it was too large then it wouldn't be dense enough to be a neutron star). It seems like the likely radii for neutron stars are around 10km. There is also this idea: http://en.wikipedia.org/wiki/Quark_star http://en.wikipedia.org/wiki/Quark_star
  - mtdewcmu 13y ago
    This area of astronomy still contains a lot of conjecture, as far as I can tell, and it could change. A recent Scientific American article made a case that black holes might not exist, but, instead, quantum mechanical effects would intervene and prevent a star from collapsing past the radius of the event horizon. They called the resulting not-quite-a-black-hole a black star (N.B., not the hip hop act featuring Mos Def and Talib Kweli). Black holes themselves are considered to have a spin, so since their radii are infinitesimal, they are the rotation champs.
deleted 13y ago
[deleted]
lutusp 13y ago
> I was hoping I could find something natural that spun faster ... A bit unrelated to your comment, but the original experimenters could have spun a buckyball instead of a sphere of calcium carbonate and gotten much, much higher rotational velocities. I hope they think of this.
- jlgreco 13y ago
  Are buckyballs big enough to hit with their laser?
- dalke 13y ago
  Can you kindly explain how even a UV laser, with a wavelength of about 200 nm, can apply enough torque on a buckyball about 1.1 nm across? My first thought was that the EM field would be essentially uniform, so what you propose wouldn't be possible. What am I missing?
  - lutusp 13y ago
    > Can you kindly explain how even a UV laser, with a wavelength of about 200 nm, can apply enough torque on a buckyball about 1.1 nm across? No chance. But it turns out there are larger fullerenes: http://en.wikipedia.org/wiki/Fullerene#Other_buckyballs http://en.wikipedia.org/wiki/Fullerene#Other_buckyballs But as it turns out, the larger fullerenes aren't as strong as C60, so my original idea probably wouldn't represent any easily achieved advantage.
    - dalke 13y ago
      As jlarocco and others point out, based on astronomical evidence, we know that C60 buckyballs are plenty strong enough to rotate at a much higher speed than this macroscopic experiment: For example, "Hydrogenated fullerenes and the anomalous microwave emission of the dark cloud LDN 1622" (www.iac.es/folleto/research/preprints/files/PP06009.ps ) says: > The recent detection of anomalous microwave emission (5–60 GHz) in LDN 1622 by Casassus et al. can be explained as the result of electric dipole radiation from hydrogenated fullerenes. The bulk of the emission (10–30 GHz) appears to be associated with 60–80 carbon atoms fulleranes with a degree of hydrogenation of C:H ≈ 3:1. ... > The emissivity of fulleranes with more than 240 atoms are already two orders of magnitude smaller than that of the C60 hydride and peaks at a frequency of ∼3 GHz, far below the frequencies relevant to the anomalous emission detected in the cloud. It looks like C240 should be able to handle 1GHz rotational speeds without a problem.

by jlgreco 13y ago

jlarocco 13y ago

Apparently some dust particles in space spin up to 10 billion times a second: http://news.nationalgeographic.com/news/2011/01/110111-fastest-dust-spinning-universe-planck-microwave-science-space/ http://news.nationalgeographic.com/news/2011/01/110111-faste... No idea how they came up with that, though.

OnACoffeeBreak 13y ago
This article claims that spin rate is directly proportional to radio frequency emitted by the dust: http://www.economist.com/node/863276 http://www.economist.com/node/863276 > What is impressive is the rate at which the particles spin. It has to be equal to the frequency of the radio wave that is emitted, so Dr Finkbeiner's observations imply that many of the dust particles are rotating at ten billion revolutions per second.

ctdonath 13y ago

Surface of that moves about 18% of light speed, closer to what I was hoping to find. ETA: That's assuming a 12km radius, per Wikipedia.

jlgreco 13y ago
Yeah, only possible I imagine because the extreme gravitational forces, having already overcome electron degeneracy pressure, can hold it together when spinning at those speeds. My thinking is that this would allow you to get a neutron star spinning much faster, and, but a neutron star just retains angular momentum from the parent star which apparently doesn't get something that large spinning all that fast.
- mtdewcmu 13y ago
  18% of the speed of light at the surface means that it could only spin slightly more than 5x faster without violating known physics. That isn't fast enough? If you want an in depth breakdown of this scenario, try posting a question at physicsforums.com. Be advised to follow their rules, though. Personal theories by non-physicists are severely punished (I made this mistake once).

Groxx 13y ago

Well, in some ways that is faster. Even if it's only 100m across (I assume it's larger than this), it spins at 223km/s at the surface. It would hit light speed at only 133km across (assuming I plugged those numbers correctly), so it must be smaller than that, which is a pretty small star.

jlgreco 13y ago
Neutron stars are bounded by mass, somewhere in the neighborhood of 3 solar units it seems (if it were more massive it would collapse further), so I think their radius is bounded too (since if it was too large then it wouldn't be dense enough to be a neutron star). It seems like the likely radii for neutron stars are around 10km. There is also this idea: http://en.wikipedia.org/wiki/Quark_star http://en.wikipedia.org/wiki/Quark_star
- mtdewcmu 13y ago
  This area of astronomy still contains a lot of conjecture, as far as I can tell, and it could change. A recent Scientific American article made a case that black holes might not exist, but, instead, quantum mechanical effects would intervene and prevent a star from collapsing past the radius of the event horizon. They called the resulting not-quite-a-black-hole a black star (N.B., not the hip hop act featuring Mos Def and Talib Kweli). Black holes themselves are considered to have a spin, so since their radii are infinitesimal, they are the rotation champs.

deleted 13y ago

[deleted]

lutusp 13y ago

> I was hoping I could find something natural that spun faster ... A bit unrelated to your comment, but the original experimenters could have spun a buckyball instead of a sphere of calcium carbonate and gotten much, much higher rotational velocities. I hope they think of this.

jlgreco 13y ago
Are buckyballs big enough to hit with their laser?
dalke 13y ago
Can you kindly explain how even a UV laser, with a wavelength of about 200 nm, can apply enough torque on a buckyball about 1.1 nm across? My first thought was that the EM field would be essentially uniform, so what you propose wouldn't be possible. What am I missing?
- lutusp 13y ago
  > Can you kindly explain how even a UV laser, with a wavelength of about 200 nm, can apply enough torque on a buckyball about 1.1 nm across? No chance. But it turns out there are larger fullerenes: http://en.wikipedia.org/wiki/Fullerene#Other_buckyballs http://en.wikipedia.org/wiki/Fullerene#Other_buckyballs But as it turns out, the larger fullerenes aren't as strong as C60, so my original idea probably wouldn't represent any easily achieved advantage.
  - dalke 13y ago
    As jlarocco and others point out, based on astronomical evidence, we know that C60 buckyballs are plenty strong enough to rotate at a much higher speed than this macroscopic experiment: For example, "Hydrogenated fullerenes and the anomalous microwave emission of the dark cloud LDN 1622" (www.iac.es/folleto/research/preprints/files/PP06009.ps ) says: > The recent detection of anomalous microwave emission (5–60 GHz) in LDN 1622 by Casassus et al. can be explained as the result of electric dipole radiation from hydrogenated fullerenes. The bulk of the emission (10–30 GHz) appears to be associated with 60–80 carbon atoms fulleranes with a degree of hydrogenation of C:H ≈ 3:1. ... > The emissivity of fulleranes with more than 240 atoms are already two orders of magnitude smaller than that of the C60 hydride and peaks at a frequency of ∼3 GHz, far below the frequencies relevant to the anomalous emission detected in the cloud. It looks like C240 should be able to handle 1GHz rotational speeds without a problem.