Einstein's Gravitational Waves May Set Speed Limit For Pulsar Spin

(Ron Baalke) wrote in message ...
Nancy Neal
Headquarters, Washington July 2, 2003
(Phone: 202/358-1547)

Bill Steigerwald
Goddard Space Flight Center, Greenbelt, Md.
(Phone: 301/286-5017)

RELEASE: 03-224

EINSTEIN'S GRAVITATIONAL WAVES MAY SET SPEED LIMIT FOR PULSAR
SPIN

Gravitational radiation, ripples in the fabric of space
predicted by Albert Einstein, may serve as a cosmic traffic
enforcer, protecting reckless pulsars from spinning too fast
and blowing apart, according to a report published in the
July 3 issue of Nature.

Pulsars, the fastest spinning stars in the Universe, are the
core remains of exploded stars, containing the mass of our
Sun compressed into a sphere about 10 miles across. Some
pulsars gain speed by pulling in gas from a neighboring star,
reaching spin rates of nearly one revolution per millisecond,
or almost 20 percent light speed. These "millisecond" pulsars
would fly apart if they gained much more speed.

...
http://www.gsfc.nasa.gov/topstory/20...lsarspeed.html

Another possibility is that the generation of pulsar pulses requires
the existence of orbiting planets in a manner analogous to how Io
directs the production and period of EM radiation from Jupiter. Then
the origin of the limitation to the rate of pulsar pulses may be the
Roche limit for planets in orbit about the pulsar (close-in planets
have shorter orbital periods thus generating shorter periods for the
pulses):


================================================== =========================
================================================== =========================
From: Robert Clark )
Subject: 'Undead' star torpedoes current theories (Forwarded)
Newsgroups: sci.astro, sci.physics
Date: 1999/08/26

In article ,
wrote:

'Undead' star torpedoes current theories

Media Release: Wednesday, 25 August 1999 Ref 1999/190

Using CSIRO data a West Australian PhD student has found a star that is not
supposed to exist. His discovery is published in today's issue of the journal Nature.

Matthew Young of the University of Western Australia studies pulsars -- small
spinning stars which send out beams of radio waves. As a pulsar spins its beam
sweeps over the Earth and we see a radio 'blip'. By taking the pulsar's pulse
astronomers measure how fast the star is spinning.

The new pulsar, called PSR J2144-3933, spins only once every eight seconds.
"This is supposed to be way too slow," explains Mr Young.

"The theory says pulsars that spin slower than once every few seconds don't have
the energy to put out pulses -- their heartbeat stops and they die. This pulsar
is on the slab, so to speak, but its heart is still beating. By rights it should
be a corpse."

...
"For almost thirty years we've thought that pulsar beams are powered by an
exotic process that makes matter and anti-matter. The theory also says that this
pulsar spins too slowly for that process to occur -- that it shouldn't be
putting out radio waves. But it is."

There are a few things that could be wrong, he says.

"Perhaps the matter and anti-matter process is going on, but it can happen at
lower spin rates than we thought. Or perhaps the pulses are powered by something
else. Whatever the case, the theory needs a rethink."

Finding this pulsar implies that the pulsar population is a lot 'greyer' than
was thought.

"We found this pulsar only because it's relatively nearby -- about 600
light-years away," says Mr Young. "It has a small beam and a fairly weak signal.
This means there could be a lot more slow, old pulsars lurking out there
undetected. Our best guess is about 100 000 in the Galaxy -- as many as all the
other pulsars put together."


"As well, astronomers just love having these super-accurate clocks flying around
in space, because they can be used to work out all sorts of things about the
stars they orbit and even the space between the stars. One pulsar has been used
to show that gravity waves are real."
...


This reminds me of a idea I had for the origin of pulsar radio
waves. The
Earth is hit by bursts of decametric radio waves from the vicinity of
Jupiter
that are correlated with the position of Io in its orbit. See for
example:

Radio-Jupiter for Amateur Observers, By Jim Sky
http://web2.thesphere.com/SAS/bullet...1.html#Jupiter

PROJECT P5-2. JUPITER-IO MAGNETOSPHERE RADIO NOISE
http://www.elmag5.com/jupiter-io.htm

Two strong places where it occurs is when Io is at approx. 90 degrees
to the
Earth-Jupiter line.

Perhaps a similar effect is occurring in regard to pulsars in that
planets
are in orbit within the intense magnetic fields of the neutron star
generating the radio waves. This would be consistent with the fact
that the
signal was fairly weak for a slow period. This could mean the planet
generating the signal was further out with a lower orbital period and
in less
intense regions of the magnetic field generating a weaker radio
signal. Note
that there may still be radio bursts due to the pulsars rotation
itself. For
example, as discussed in the first web page above there are signals
correlated with Jupiters orbital rotation. If radio bursts associated
to an
orbiting body are a general effect then they should also exist in
regards to
Mercury and the Sun. They may be difficult to observe because of
Mercury's
distance from the Sun (being in a weaker magnetic field) and because
any such
signals are drowned out by the Sun's already intense radio emissions.
One
possibility would be to make the observations during an eclipse. If a
similar
process as with Io-Jupiter occurs, then there should be intensity
correlations to when Mercury is at 90 degrees to the Earth-Sun line.
Note
this is assuming that such radio emissions are actually emanating from
the
orbiting body itself. I don't know this to be the case. Is it known
for the
Io-Jupiter system? If it is found that there are such radio bursts
for the
Mercury-Sun system, then that opens up a possible avenue for searching
for
planets about nearby stars. It would involve searching for periodic
brightenings in a stars radio signal. Perhaps the Mercury-Sun system
produces
signals at a characteristic frequency as Io-Jupiter does at decametric
frequencies. We could look for these frequencies during such
brightenings.
For nearby stars, we could perhaps use the recent methods of
high-resolution
radio interferometry to distinguish the signal's origin as being from
the
star itself or from somewhere in orbit. For sun-like stars, we could
estimate
its mass and determine if a planet at this orbit should have an
orbital
period indicated by the periodic brightenings.


--
_______________________________________________

"In order for a scientific revolution to occur,
most scientists have to be wrong"
-- Bob Clark
_______________________________________________

================================================== =========================
================================================== =========================

From: Robert Clark )
Subject: 'Undead' star torpedoes current theories (Forwarded)
Newsgroups: sci.astro, sci.physics
Date: 1999/09/01

Thank you very much for your informative response, Dr. Arendt. My
general
sense is that the radio emissions from the Jovian system in toto are
so
complicated that they can emulate the features seen in pulsar radio
bursts
(aside from their intensity) including synchrotron radiation and
polarized
radio waves. I'm looking up some other relevant refs., but here's
one:

Ulysses Radio Observations of Jupiter
http://urap.gsfc.nasa.gov/WWW/reiner/jupiter.html

The question arises whether such emissions would exist if Jupiter
did not
have orbiting satellites. Again, my feeling is that they are directly
responsible for their complexity. Their intensity and variety would
not
nearly be as great if they weren't there. In particular there are the
intense
electron beams known to emanate from Io:

"Electron Beams and Ion Composition Measured at Io and in Its Torus",
Science, Volume 274, Number 5286 Issue of 18 Oct 1996, pp. 401 - 403
http://www.sciencemag.org/cgi/conten...t/274/5286/401

Such beams impacting the ionosphere of Jupiter have an effect on
Jupiter's
auroras. One imagines they also effect the radio emissions coming
directly
from Jupiter itself.

This proposed mechanism for the generation of pulsar radio bursts
would
have greater support if other cases of radio bursts directed by a
satellite
could be observed. I mentioned the possibility of Mercury, but there
may be
other cases. Recently there appeared a report that there could be
other
stable asteroid belts other than the one between Mars and Jupiter. As
I
recall one was very close in to the Sun, in fact inside the orbit of
Mercury.
If such radio bursts directed by satellites inside the magnetic fields
of a
parent body are a general phenomenon, they should also exist in this
case. As
with the case with Mercury, there would be the problem of
distinguishing
these bursts from the general radio emissions from the Sun. Again it
might
help to make such observations during an eclipse. There should be a
correlation between the period of such bursts and their origin's
distance
from the Sun as there is between the period and distance of a
satellite of
the Sun.


--
________________________________________________

"In order for a scientific revolution to occur,
most scientists have to be wrong"
-- Bob Clark
________________________________________________


In article ,
(Paul Arendt) wrote:
In article ,
Robert Clark wrote:
In article ,
wrote:
'Undead' star torpedoes current theories

Media Release: Wednesday, 25 August 1999 Ref 1999/190

Using CSIRO data a West Australian PhD student has found a star that is not
supposed to exist. His discovery is published in today's issue of the
journal Nature.

The new pulsar, called PSR J2144-3933, spins only once every eight seconds.
"This is supposed to be way too slow," explains Mr Young.

For the record, there are (at least) two distinct types of pulsars known:
"rotation-powered," which are typically seen in the radio, and whose spin
rate (usually) gradually and smoothly decreases with time. The newly
discovered pulsar sounds like it's in this class. Previously, the range
of known periods (for over 1,000 known pulsars) went from a few
milliseconds to about 4.5 seconds -- a factor of about 1,000. This new
object increases that range by another factor of two (almost).

There are *also* "accretion-powered" pulsars. These are objects whose
spin rate changes with time, often rapidly switching between speeding-up
and slowing-down. These latter objects are typically seen in the X-ray
regime, and typically have much longer periods. Eight seconds is a
*normal* period for these to have, but I think slower and faster objects
of this type are also known.

The difference is almost certainly that the accretion-powered stars have
a nearby companion which is shedding mass onto it (in an accretion disk),
and changes the angular momentum both up and down depending on exactly
how stuff falls onto the pulsar. The rotation-powered ones don't have
a (very) nearby mass-shedding companion, although the fastest
("millisecond") ones probably had one in the past.

"The theory says pulsars that spin slower than once every few seconds don't
have
the energy to put out pulses -- their heartbeat stops and they die. This
pulsar
is on the slab, so to speak, but its heart is still beating. By rights it
should
be a corpse."
...
"For almost thirty years we've thought that pulsar beams are powered by an
exotic process that makes matter and anti-matter. The theory also says
that this
pulsar spins too slowly for that process to occur -- that it shouldn't be
putting out radio waves. But it is."

Historically, the theory developed around the observations! So it's not
surprising that it says pulsars shouldn't be seen outside the known range:
people tried to explain *why* we didn't see any pulsars outside the
known range!

"Perhaps the matter and anti-matter process is going on, but it can
happen at
lower spin rates than we thought. Or perhaps the pulses are powered by
something
else. Whatever the case, the theory needs a rethink."

The theory is flexible enough to accomodate the new spin rate without too
much trouble, I'd bet. But the new issue of Nature hasn't shown up at
the library here yet, so I haven't seen the paper.

It would be much MORE of a "torpedo to current theories" to find a pulsar
at a spin rate a factor of two FASTER than the fastest known ones. In
fact, it would probably net the discoverer a Nobel Prize, as the first
direct evidence of a "quark star," in the most likely scenario. Searches
are underway to check for these fast-period objects, but it's tough to
see a periodic signal when you don't yet know what the period is (unless
it's very, very bright).

But it is neat that this was discovered -- anything outside of known
boundaries usually is!

This reminds me of a idea I had for the origin of pulsar radio waves. The
Earth is hit by bursts of decametric radio waves from the vicinity of Jupiter
that are correlated with the position of Io in its orbit.
...
Perhaps a similar effect is occurring in regard to pulsars in that planets
are in orbit within the intense magnetic fields of the neutron star
generating the radio waves. This would be consistent with the fact that the
signal was fairly weak for a slow period.

This isn't likely. For one, all the fast-period pulsars would be tough
to explain, since planets can't orbit the neutron star that fast! For
another, polarization data indicate that we're seeing emission from a
magnetic pole as the star spins past. It would be VERY tough to explain
the polarization data with a Jupiter-Io scenario.

================================================== =========================
================================================== =========================