27
votes
Accepted
What causes fast moving pulsars to move so fast?
The most likely scenario is that an asymmetry in the supernova explosion imparts momentum to the proto neutron star at its core. The issue is not settled.
A recent study by Verbunt et al. (2017) ...
- 115k
22
votes
Accepted
Rotation direction of Pulsars
Does the Earth rotate clockwise or anticlockwise?
If you are floating above the north pole of Earth you would see the Earth rotating anticlockwise(*) if you were floating above the south pole, you ...
- 88.7k
18
votes
What is the probability of seeing a neutron star as a pulsar?
Out of 100 pulsars, how many will have a beam that crosses the Earth?
About twelve.
"The beaming fraction f , that is the mean value of the fraction of observable pulsars or the mean probability of ...
- 1,760
18
votes
Accepted
What is the probability of seeing a neutron star as a pulsar?
The probability of seeing pulsed emission from a neutron star is simply the fraction of the sky covered by the beam, i.e. the beam solid angle divided by $4\pi$ steradians.
The angle swept out on the ...
- 33.8k
17
votes
Pulses from a pulsar
The key is to compare the range of pulsar periods and ther behaviour with the typical dynamical timescales of stars. Pulsar periods range from just less than $10^{-3}$ s to $\sim 10$ s. And $\dot{P}$ ...
- 115k
14
votes
Accepted
How Would a Neutron Star Actually Appear?
Your question is too general, you need to get to specific examples.
First, very few neutron stars are pulsars. Pulsars are either a brief phase during a pulsar's spin-down at the start of a neutron ...
- 115k
13
votes
Accepted
Are there neutron stars whose magnetic axis and rotating axis are the same, and if so what will happen?
It is believed that old pulsars may have their rotational axes closely aligned with their magnetic field. This would happen over a timescale of $\tau\sim10^7$ years (Lyne & Manchester (1988)). ...
- 33.8k
8
votes
Accepted
Does the observed period of a pulsar change with the time of year?
Yes. In terms of pulsar timing measurements, this is a massive effect! A +/- 30 km/s doppler shift changes the pulsar frequency by +/- 1 part in 10000. This sounds small, but the accumulated phase ...
- 115k
8
votes
Accepted
Can we detect pulsars that aren't "pointed" towards us?
They don't need to be pointed exactly at us, since the angular beam radius is a few degrees (Pulsar Astronomy, P. 212) but there is a portion that we can't detect, described by a beaming factor (P. ...
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8
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Do the neutrons in neutron stars emit the radio waves?
The electromagnetic radiation comes from accelerated charged particles, mainly electrons and positrons.
The surface of a neutron star is not made of neutrons. It is a totally ionised gas of nuclei ...
- 115k
7
votes
Accepted
Why do pulsars turn "off" from rotation?
The first thing you need to recall is that electromagnetic waves do carry momentum as well as energy. This shows up in effects like light pressure. Specifically a photon of wavelength $\lambda$ ...
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7
votes
Accepted
Is there a Vela Nebula?
The Vela Pulsar (PSR J0835-4510 or PSR B0833-45) is a radio, optical, X-ray- and gamma-emitting pulsar associated with the Vela Supernova Remnant in the constellation of Vela.
First line of the ...
- 115k
7
votes
Accepted
Is there any well-populated list or database of pulsar "glitches"?
There are two substantial (~650 entries) glitch databases I'm aware of, one maintained by Jodrell Bank and one maintained as part of the ATNF's pulsar catalog. Both list similar information for each ...
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6
votes
Accepted
Does Doppler shift affect apparent pulsar frequency?
Yes, it is correct.
Consider the classic example of a (say) $1000$ Hz siren on an ambulance approaching you. Once a single wave is produced, the source moves towards you before the next wave is ...
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6
votes
Accepted
What is a typical polar angle of a pulsar beam?
Typical angles can span the range from several degrees to close to $90^{\circ}$ in some extreme cases. For pulsars with narrow emission cones, the opening angle of the emission cone is approximately
$$...
- 33.8k
5
votes
Accepted
Pulsars: How do astronomers measure minute changes in period (~picoseconds per year)?
Let us suppose that the pulsar is spinning down at a uniform rate. So it has a period $P$ and a rate of change of period $dP/dt$ that is positive and constant (in practice there are also second, third,...
- 115k
5
votes
What causes a star to become a pulsar?
The endpoint in the lives of massive stars between about 10 and 25 solar masses is thought to be a core-collapse supernova that produces a condensed remnant called a neutron star.
The lower mass ...
- 115k
5
votes
Why are the magnetic poles of a pulsar so far off the rotational axis, yet stable?
The magnetic field of a star is not entirely a result of the global spin of the star. The global spin is part of it, but there are other mechanisms as well. Within the star, there are convection zones,...
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5
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Does the observed period of a pulsar change with the time of year?
Short answer is: yes.
Longer answer is: correcting for the time dilation effects of Earth moving around the Sun's gravitational potential is actually relatively standard in almost all branches of ...
- 176
5
votes
How do I make a custom pulsar map?
The pulsar map used by Pioneer and Voyager is a diagram of the position of the Sun relative to 14 galactic pulsars. It encodes their positions, distances, and pulse periods, which in theory makes it a ...
- 33.8k
5
votes
Accepted
How bright is the Crab Pulsar's 30 Hz modulation in visible light? What color is it?
The optical pulsations of the Crab pulsar have been studied closely since 1969. The observations are actually not that difficult (I did some myself with a photoelectric photometer as a student) and ...
- 115k
5
votes
Accepted
Why pulsar pulses are so extremely regular?
Pulsars are precise because... in essence, there isn't much to cause them to be imprecise. It's as if you spun a top in intergalactic space and left it there for a hundred years - it would likely ...
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5
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Are there neutron stars whose magnetic axis and rotating axis are the same, and if so what will happen?
NICER observations of PSR J0030+0451 in x-rays show hot spots clustered near one pole. The hot spots are presumed to be the termination of the active magnetic field lines, so there is really no ...
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5
votes
If a pulsar's rotational and magnetic axes were aligned and both aimed at us, would we see a steady radio source?
Two things would be required. First, your line of sight would have to be close to looking along the magnetic axis of the neutron star. Second, that magnetic axis would have to be closely aligned with ...
- 115k
5
votes
Accepted
What exactly is "the rotating lighthouse model" in the context of a double pulsar?
It seems that the authors are just referring to the accepted model of a pulsar, i.e. a neutron star spinning and emitting beams of radiation at its poles. In that sense, the term is used here no ...
- 33.8k
5
votes
Accepted
Is "magnetars don't last long — just a year to a few years" really true? Is it a misquote or perhaps taken out of context?
It's certainly not true. I've watched the linked video and read the linked articles, and even with that additional context, I don't see a way for the quote to fit with our understanding of the ...
- 33.8k
4
votes
Rule of Exception in All Nearest Objects
I have not heard of any idea that the nearest object is exceptional in any significant way, and in the case of the nearest pulsar, nearest star, nearest (large) galaxy etc. the properties are usually ...
- 115k
4
votes
Can't pulsars and stars be used for gravitational wave measurement?
How LIGO, LISA, etc. Detect Gravitational Waves
The point of instruments like LIGO and LISA is to measure time-varying changes in the distance within different arms of the instrument. In the case of ...
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4
votes
Accepted
How are pulsars detected from Earth?
the signal period of known pulsars is 1 ms-15 s (0.07-1,000 Hz since F=1/T).
That's the frequency of how often the signals occur, not the frequency of the waves they emit. Just compare it to a ...
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