18
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 observing a normal pulsar, is 0.124 ± 0.004." M. Kolonko et al.: On the pulse-width statistics in radio pulsars
17
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 sky by a pulsar with an emission cone of width $\rho$ turns out to be
$$\zeta=4\pi\sin^2\left(\frac{\rho}{2}\right)$$
covering a fraction of the sky
$$f=\frac{...
13
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)). There are three sets of phenomena driving the dynamics of the alignment (Casini & Montemayor (1998)):
Short-term ($\sim50$ days) variations caused by glitches
...
5
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 magnetic "axis". The field is more complicated.
First surface map of a pulsar
4
A priori it is very difficult to distinguish the origin of any particular feature from just one image.
For that reason it is established workflow, especially in astronomical context, to create 4 kind of images:
the light frame R. That's the actual image of what you are interested
in
the dark frame D. That's an exposure of identical length and at
identical ...
3
That is what is done. This is shown in an old xkcd comic https://xkcd.com/54/
The curve shows the distribution of frequencies in the CMB, and by using the marked value of the maximum you can determine the value of T, the apparent (red-shifted) temperature of the CMB
3
The other answers cover the geometric part, but that only tells you what fraction of pulsars are seen as such from Earth. The other issue is what fraction of neutron stars are pulsars at all. If they don't pulse, and they don't do something else conspicuous like accrete from a binary companion, neutron stars are very difficult to find. A common rough ...
2
You can get into observational astronomy from a range of backgrounds. Some easily, some less so. Physics and data science sounds like a very fine choice as that is what can be a large part of an observational astronomer.
You probably will have to learn a bit about image processing. And possibly about the physics of the objects you are going to observe. Such ...
2
There have been direct measurements, but they are quite delicate -- this is all the interferometry and so on.
The simplest way though is based on spectroscopy, brightness and parallax. The argument goes a follows:
The spectrum (how much light of each colour it gives off) is not hard to observe -- you basically just need a prism.
The spectrum of most stars ...
1
Here is what I have gathered.
SWAN seems to be on a parabolic orbit. This means that it is the first time that it is interacting with the Sun, making it a "new" comet. New comets are covered in a layer of very volatile elements that will vaporize pretty fast when the comet is still far away from the Sun. This causes a surge in brightness. But once those ...
1
I asked the at the minor planet center how the codes were decided, and the answer was
Historically, the observatory codes were assigned ascending by longitude toward east (from prime meridian): 360 degrees were divided by numbers. When three digit numerical codes were not sufficient, letters plus two numbers were used again in bands toward the east. Some ...
Only top voted, non community-wiki answers of a minimum length are eligible
