What is a pulsating star?
1 Answer
A pulsar.
Explanation:
A pulsating neutron star or pulsar is a extremely high density star remnant. A neutron star forms when a massive star undergoes supernova. Generally this star needs to start more than 8 times bigger than our sun, but at about 30 times bigger than our sun the star is giant enough to turn into a black hole after supernova. Even though these remnants have at more mass of our sun the neutron star is much smaller than even our moon. So a sugar cube size of the matter would weight about as much as a mountain.
Anyway, if the neutron star is rotating at a very high speed (fastest is over 35000 rpm). The speed comes from the conservation of angular momentum. That is the main star was rotating, so as it shrunk down due to gravitational collapse the rotation sped up to maintain the momentum.
Finally, the star has to be emitting energy. The energy is generated in a few different possible ways but we can save that for another question. Due to the rotation of the pulsar the energy actually shots out of the poles in a beam. Now if you imaging the rotating beacon of an airport, from a distance it seems like it is pulsing, but on closer inspection it is not pulsing at all but seems like it is from a stationary point due to the rotation. So pulsars do not actually "pulse".
This graphic will hopefully make things clearer. If you were at a great distance from this you would only see the beam as it swept over your location making it appear as a pulse.
