28
1 Introduction to the Pulsars
matter to the quark matter will change continuously. Generally, the types of these
neutron stars are referred to as hybrid stars.
1.4.4 Physical Conditions
Pulsars are the neutron stars with highly rapid rotating, and have the extreme physical conditions, such as extremely strong gravitational field, extremely high density,
extremely high temperature and pressure, as well as extremely strong magnetic field
and electric field.
A typical radius of pulsar is only about 10 km and it has a mass of 1.44−3.2
solar masses. Therefore, the gravity on the pulsar’s surface is so strong that it is
very difficult for any matter to escape the gravitational constraints, and even light
is able to break away from the constraints only by a way of parabolic curve. Most
free electrons are squeezed into the atomic nuclei by the extremely strong gravity of
pulsars, and then the electrons are forced to combine with the protons to form the
neutrons.
It is known from the above that the internal structure of typical pulsar is divided
into five segments from the outer to the inner. The solid outer crust layer below the
atmosphere takes on a crystalline lattice structure, where the matter is composed of
neutron nuclei and electrons, and the density increased rapidly and up to an order
of 10
3
−10
8 kg/cm
3 . Below the outer crust layer, the density of the inner crust layer
has been more than 4.0 × 10
8 kg/cm
3 . The neutron matter region is just below the
inner crust layer and its matter consists of the degenerated neutron fluid as well as a
few of protons and electrons. In the region, the neutrons appear on super-fluid states
and the atoms do on super-conduction ones, and the density is more than an order
of 10
11 kg/cm
3 . The core region of neutron star is a solid core with a range of about
1 km, and its density is 2−3 times that of the atomic nuclei. There is no other place
in the universe where the physics of so high density matter can be investigated.
The temperature on the surfaces of neutron stars are about 10
7 K, and the core
temperature inside neutron stars up to 6 × 10
9 K. The core pressures of neutron
stars are up to an order of 10
28 atm, which is 3 × 10
16 times that of the Sun’s core.
Therefore, neutron stars are much hotter than the Sun, and have extremely high
temperature and pressure environments.
The interiors of neutron stars are filled with plasmas. During the star evolving,
the magnetic fields have been reserved by the plasmas. It is shown by theoretical
calculations that if the magnetic field strength of a main sequence star is 10
–2 T (1T
= 10
4 Gauss), the magnetic field of the neutron star formed by the star evolving
will get to 10
8 T. It is seen from the actual observations that the magnetic fields of
ordinary pulsars are typically 10
6
−10
8 T, while those of the AX pulsars can reach
10
14 T. The magnetic field on the surface of a neutron star is 2 × 10
13 times that
of the Sun and 10
16 times that of the Earth. It is well known that a rapidly rotating
magnetic field will produce the electric field. So, the electric fields on the surfaces
of pulsars are also extremely strong and up to 10
14 V/m.
1 Introduction to the Pulsars
matter to the quark matter will change continuously. Generally, the types of these
neutron stars are referred to as hybrid stars.
1.4.4 Physical Conditions
Pulsars are the neutron stars with highly rapid rotating, and have the extreme physical conditions, such as extremely strong gravitational field, extremely high density,
extremely high temperature and pressure, as well as extremely strong magnetic field
and electric field.
A typical radius of pulsar is only about 10 km and it has a mass of 1.44−3.2
solar masses. Therefore, the gravity on the pulsar’s surface is so strong that it is
very difficult for any matter to escape the gravitational constraints, and even light
is able to break away from the constraints only by a way of parabolic curve. Most
free electrons are squeezed into the atomic nuclei by the extremely strong gravity of
pulsars, and then the electrons are forced to combine with the protons to form the
neutrons.
It is known from the above that the internal structure of typical pulsar is divided
into five segments from the outer to the inner. The solid outer crust layer below the
atmosphere takes on a crystalline lattice structure, where the matter is composed of
neutron nuclei and electrons, and the density increased rapidly and up to an order
of 10
3
−10
8 kg/cm
3 . Below the outer crust layer, the density of the inner crust layer
has been more than 4.0 × 10
8 kg/cm
3 . The neutron matter region is just below the
inner crust layer and its matter consists of the degenerated neutron fluid as well as a
few of protons and electrons. In the region, the neutrons appear on super-fluid states
and the atoms do on super-conduction ones, and the density is more than an order
of 10
11 kg/cm
3 . The core region of neutron star is a solid core with a range of about
1 km, and its density is 2−3 times that of the atomic nuclei. There is no other place
in the universe where the physics of so high density matter can be investigated.
The temperature on the surfaces of neutron stars are about 10
7 K, and the core
temperature inside neutron stars up to 6 × 10
9 K. The core pressures of neutron
stars are up to an order of 10
28 atm, which is 3 × 10
16 times that of the Sun’s core.
Therefore, neutron stars are much hotter than the Sun, and have extremely high
temperature and pressure environments.
The interiors of neutron stars are filled with plasmas. During the star evolving,
the magnetic fields have been reserved by the plasmas. It is shown by theoretical
calculations that if the magnetic field strength of a main sequence star is 10
–2 T (1T
= 10
4 Gauss), the magnetic field of the neutron star formed by the star evolving
will get to 10
8 T. It is seen from the actual observations that the magnetic fields of
ordinary pulsars are typically 10
6
−10
8 T, while those of the AX pulsars can reach
10
14 T. The magnetic field on the surface of a neutron star is 2 × 10
13 times that
of the Sun and 10
16 times that of the Earth. It is well known that a rapidly rotating
magnetic field will produce the electric field. So, the electric fields on the surfaces
of pulsars are also extremely strong and up to 10
14 V/m.