# How does a pulsar die?

1. Jan 1, 2005

### Vale1219

Hello!
I just want to know how does a pulsar die, if it dies someday...????

2. Jan 1, 2005

### dsmaum

Hello,

Pulsars or any star will eventually(depending on its size) die, i.e. burn out its all Hydrogen,etc. and for that matter, nothing in this world is permanent!

3. Jan 1, 2005

### Janus

Staff Emeritus
There are three types of pulsars all three are neutron stars:

Rotational
X-ray (or Accretion)
magnetars.

Rotational Pulsars generate their radiation from their rotation, which means as time goes by, their rotation slows. So this type of pulsar "dies" when it has given up all its rotational energy.

X-ray Pulsars form when a neutron star has a binary companion. When the companion, in the course of passing through its life, begins to expand, It can leak material to the Neutron star as accretion matter. It is this accreation matter that provides the energy for the pulses. Such a pulsar would "die" when it ran out of accretion matter. (though the accretion matter can add angular momentum to the neutron star and "spin it up" so that it now becomes a rotational pulsar, which eventually dies in the manner of these types of pulsars.)

Magnetars get their energy from the decay of a very strong magnetic field. So these pulsars "die" when the field has decayed to a low enough level.

4. Jan 1, 2005

### meteor

Pulsars emit electromagnetic radiation along its magnetic axis, and they spin around its rotational axis. Pulsars slow down over time. The spindown of a pulsar can be characterized by the braking index n
$$n=\frac{\ddot{\Omega}\Omega}{\dot{\Omega^{2}}}$$
(Reference http://www.phys.unm.edu/~duric/phy536/16/node4.html [Broken])
The fastest pulsar that I know is PSR 1937+21 that spins at 660 rev/sec, while in the other extreme the slowest pulsar that I know is J2144-3933, with a period of 8.51 sec.
Some pulsars would stop rotating before they do it if it wouldn't be the case that they accrete material from a star and this accretion accelerates again the rate of rotation of the pulsar. These are known as "recycled pulsars"
A curiosity: some pulsars stop to emit pulses during a certain time and then return to their routine. This "vacation" of the pulsar is known as nulling
Regards

Last edited by a moderator: May 1, 2017
5. Jan 1, 2005

### Labguy

And, #4. Some Pulsars (neutron stars) that are accreting matter from a companion will build enough mass to pass the ~3.2 solar mass "Oppenheimer limit" (upper limit for Neutron stars) and can collapse causing a supernova and/or Black Hole.

Last edited: Jan 1, 2005
6. Jan 4, 2005

### Nereid

Staff Emeritus
Welcome to Physics Forums Vale1219 and dsmaum!

The four 'deaths' so far described are the end of pulsars 'at home', and 'as pulsars'.

A pulsar may also 'die' not by losing its pulse, but because the pulses become invisible to us here on Earth - maybe because the alignment is lost (precession of the pulsar, relative motion).

In another sense, a pulsar is still 'alive' even when it's no longer emiting beams ... it may still be hot enough to emit light, or X-rays, or radio. Or it may 'swallow' a chunk of passing mass (a 'rogue planet' perhaps?), and start flaring for a while. Or as it cools, there may be a 'starquake', which we may see as a different type of flare.

Eventually however, it will suffer the same fate as white dwarfs, red dwarfs, brown dwarfs, ... it will simply cool down and come to equilibrium with the CMBR (which by then may be a bit cooler than it is now).