8
1 Introduction to the Pulsars
from the scintillation source were very regular and once pulsating signal could be
recorded every 1.3373 s. The pulse is itself about 20 ms wide, and it was also shown
that the radio source’s size would not be greater than the Earth and must have come
from outside the solar system. Meanwhile, by carefully studying a lot of recorded
observation data, Jocelyn Bell found that there were similar phenomena and still three
scintillation sources with similar regularity. At that time, a science fiction novel was
being popular in the United Kingdom. The extraterrestrial intelligence is described
as the Little Green Man (LGM) in this novel. At first, the research team guessed
that these unusual signals came possibly from an extraterrestrial civilization, and
hence the four scintillation sources discovered first were catalogued respectively as
LGM-1, LGM-2, LGM-3 and LGM-4.
Apparently, any extraterrestrial intelligence should live on the planets orbiting
around a star, and the signals from the planets would have the Doppler frequency
shifts. However, the pulsating signals obtained by the research team only have the
Doppler frequency shifts resulted from the Earth orbiting around the Sun, while
there are not the phenomena of the radio sources moving. Moreover, the four discovered pulsating signals come respectively from different directions in the universe, and
thereby it is impossible that the extraterrestrial intelligence lived in the different locations would emit coincidentally the same kind of signals. Finally, it was confirmed by
the research team that the radio sources were the pulsating signals emitted from the
natural celestial objects outside the solar system, and were named pulsars. Furthermore, the first discovered pulsar was also called CP 1919, where “C” denotes the
Cambridge, “P” denotes the pulsar and “1919” denotes the right ascension expressed
by hour and minute, also known as 19h19min.
1.2.3 The Pulsars Identified as Neutron Stars
In February 1968, Hewish and Bell, et al. published their classic paper in the Nature,
entitled “Observation of a Rapidly Pulsating Radio Source” [6, 7]. In this paper, they
declared: an unusual radio source located in outside the solar system was discovered;
it emitted a short and regular radio pulse, known as pulsar; it was pointed out that
the density of the pulsar was very high, and possibly the neutron star ever predicted
theoretically more than 30 years ago. Moreover, it was also thought in this paper that
the pulsating periodicity was resulted from the oscillation of the neutron star along
its radial direction. Apparently, it has been confirmed presently that the deduction of
the radial oscillation is wrong. In 1974, Antony Hewish and his colleague, another
radio astronomers Martin Ryle (1918−1984), were together awarded the Nobel Prize
in physics by the Royal Swedish Academy of Science for their pioneering research
in radio astrophysics: Ryle for his observation and inventions, in particular of the
aperture synthesis technique, and Hewish for his decisive role in the discovery of
pulsars.
A few days before the Nature letter appeared, the discovery of the pulsar was
discussed at a colloquium at the University of Cambridge. The news spread rapidly
1 Introduction to the Pulsars
from the scintillation source were very regular and once pulsating signal could be
recorded every 1.3373 s. The pulse is itself about 20 ms wide, and it was also shown
that the radio source’s size would not be greater than the Earth and must have come
from outside the solar system. Meanwhile, by carefully studying a lot of recorded
observation data, Jocelyn Bell found that there were similar phenomena and still three
scintillation sources with similar regularity. At that time, a science fiction novel was
being popular in the United Kingdom. The extraterrestrial intelligence is described
as the Little Green Man (LGM) in this novel. At first, the research team guessed
that these unusual signals came possibly from an extraterrestrial civilization, and
hence the four scintillation sources discovered first were catalogued respectively as
LGM-1, LGM-2, LGM-3 and LGM-4.
Apparently, any extraterrestrial intelligence should live on the planets orbiting
around a star, and the signals from the planets would have the Doppler frequency
shifts. However, the pulsating signals obtained by the research team only have the
Doppler frequency shifts resulted from the Earth orbiting around the Sun, while
there are not the phenomena of the radio sources moving. Moreover, the four discovered pulsating signals come respectively from different directions in the universe, and
thereby it is impossible that the extraterrestrial intelligence lived in the different locations would emit coincidentally the same kind of signals. Finally, it was confirmed by
the research team that the radio sources were the pulsating signals emitted from the
natural celestial objects outside the solar system, and were named pulsars. Furthermore, the first discovered pulsar was also called CP 1919, where “C” denotes the
Cambridge, “P” denotes the pulsar and “1919” denotes the right ascension expressed
by hour and minute, also known as 19h19min.
1.2.3 The Pulsars Identified as Neutron Stars
In February 1968, Hewish and Bell, et al. published their classic paper in the Nature,
entitled “Observation of a Rapidly Pulsating Radio Source” [6, 7]. In this paper, they
declared: an unusual radio source located in outside the solar system was discovered;
it emitted a short and regular radio pulse, known as pulsar; it was pointed out that
the density of the pulsar was very high, and possibly the neutron star ever predicted
theoretically more than 30 years ago. Moreover, it was also thought in this paper that
the pulsating periodicity was resulted from the oscillation of the neutron star along
its radial direction. Apparently, it has been confirmed presently that the deduction of
the radial oscillation is wrong. In 1974, Antony Hewish and his colleague, another
radio astronomers Martin Ryle (1918−1984), were together awarded the Nobel Prize
in physics by the Royal Swedish Academy of Science for their pioneering research
in radio astrophysics: Ryle for his observation and inventions, in particular of the
aperture synthesis technique, and Hewish for his decisive role in the discovery of
pulsars.
A few days before the Nature letter appeared, the discovery of the pulsar was
discussed at a colloquium at the University of Cambridge. The news spread rapidly