Just heard this on the podcast "Mountain Radio Astronomy". Their podcast of 8 October 2005 was an interview with pulsar hunter Scott Ransom at the National Radio Astronomy Observatory in Charlottesville. Scott had - at the time of the interview - found about 30 millisecond pulsars in a globular star cluster called Terzan 5.
A pulsar is believed to be a quickly rotating neutron star, a supernova remnant, most of them rotating in less than a second. The pulsar has a rather small and directional radiating area that can only be registered when it is facing us.
A second type of even faster rotating pulsars - known as millisecond pulsars - rotating more than a 100 tomes per second, are found in globular star clusters.
The rotation period of the millisecond pulsars is extremely precise, approaching that of an atomic clock , and this means thatsome interesting measurements of pulsar orbits can be made.
About 20 minutes into the interview he talked about a measurement of a pulsar orbit with an accuracy that really surprised me.
The example here is the Hulse-Taylor star system two pulsars orbiting each other in an orbit smaller than the Sun.This can demonstrate Einstein's general theory of relativity, the interaction between spacetime and gravitation and an indication of gravity waves.
One other of the pulsars, Terzan N is orbiting a massive companion in an almost exact circular orbit about the size of the Sun.there is a little eccentricity, that is difference in the long axis and the short axis of the orbit, is measured as 48 cm +/- 6 cm. Less than half a meter ! Measured at a distance of 20 000 light years. Mind blowing ...
Science stranger than fiction ...
Link to Mountain Radio Astronomy
Link to The podcast MP3 file
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5 comments:
I hypothesise that a "pulsar" is actually the reception of a very weak continuous signal.
ie a star that is very very distant.
ie each "received" pulse is a single electron transition within the detector and thus the amplified signal can show no further detail other than the internal dynamics of an electron transition within the detector.
That is not the "conventional" view. That view theorizes that a strong local magnetic field on the surface of the neutron star comes into view through a very fast rotation of the pulsar, and according to good old Mr Maxwell, a fast changing magnetic (or electric) field generates electromagnetic waves.
And when you listen to a pulsar , the signal is definately not continous, but a series of very regular pulses.
There are recordings of pulsars on the net, so try and listen to one, It is clearly separated pulses with a constant period you are going to hear , hence the name pulsar.
That is exactly my point.
Quantum theory is bunk.
It is merely a mathematical model that is extremely useful; but it is not a devine revalation like a lot of people think.
The light/radio signal in space from a bright source is continuous.
If you try and look for it from a sufficient distance there is barely enough energy to kick the an electron "orbiting an atom" in the receiver into a higher energy state; and it takes time to accumulate that ammount of energy from the very weak continuous signal.
Terence David Carroll (UK 1962.JAN.12)
the signal from a pulsar cannot be a "continuous signal" of a distant source where each pulse is merely the detection of a single electron because of many reasons:
1. the crab nebula has a pulsar at its center, and we know the distance to this pulsar fairly accurately, and know that beyond a doubt that it is indeed a neutron star pulsar, so it cannot be a distant/continuous source
2. the spectra of these sources indicate synchrotron radiation due to the relativistic acceleration of electrons around extremely strong magnetic field lines => pulsar
I could not agree more. There are some misunderstandings out there, but we should not let that interfere with scientific knowledge.
Thanks for your comment Rob
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