Neutron stars and black holes

Why are neutron stars, despite having 1–3 solar masses, still very small in size?

because they’re so dense

what are the other important properties of neutron stars?

rotation - as the parent star collapses, the neutron core spins rapidly, conserving angular momentum and magnetic field which is the result of the collapse, neutron star’s magnetic field becomes strong

when was the first pulsar discovered?

in 1967 and it emitted extraordinarily regular pulses but they realized it was a neutron star

why would a neutron star flash on and off?

strong jets of matter are emitted at the magnetic poles - if the rotation axis isn’t the same as the magnetic axis, the beams will sweep out circular paths

what is the lighthouse model?

a model where along the magnetic field axis of a pulsar a radiation beam will be seen from earth if it happens to be directed in our direction, it will turn on/off like a lighthouse

how do pulsars radiate their energy?

they do it quickly, the radiation weakens and stops in tens of millions of years, making it virtually undetectable

what are magnetars?

a neutron star with a super-strong magnetic field a thousand trillion times stronger than earth’s and the magnetic field slows the stars’ rotation and causes starquakes that pump enough energy into the surrounding gates to generate bursts of soft gamma radiation

what is an x-ray burster?

it produces a sudden, intense flashes of x-rays, followed by a period of relative inactivity lasting as long as several hours then another burst happens which are thought to be caused by explosive nuclear burning on the surface of an accreting neutron star

what are black holes?

remains of a star that collapsed under its own gravitational force and the escape speed is very large → if the escape speed is bigger than the speed of light, the light can’t escape and appears black

what is an event horizon?

the imaginary surface of a sphere with a radius and is the limit of how close you can approach the black hole and escape

what is the schwarzchild radius?

the critical radius at which the escape speed = c

what forms an accretion disk?

light from events taking space near the black hole that should be visible, if a binary system has a black hole and a normal star, the material from the normal star can be pulled into a black hole

What happens to material as it gets closer to a black hole’s event horizon, and what kind of radiation does it emit?

the orbital height above the event horizon decreases and the temperature rises - the high temperature material radiation, extending into the x-ray region which are characteristics of black holes