1.2 The Discovery and Identification
7
1.2.2 Discovery of Pulsating Radio Sources
In 1965, Professor Hewish recruited a female doctoral graduate student, Susan
Jocelyn Bell (now Professor Bell-Burnell, 1943−). Jocelyn Bell was born in Lurgan
town in County Armagh, Northern Ireland. Her father was an architect who had
helped design the Armagh Planetarium, and during visits, she was encouraged by
the staff to pursue astronomy professionally. Young Jocelyn also found her father’s
books on astronomy. She graduated from the University of Glasgow in 1965, with
a Bachelor of Science Degree in natural philosophy (Physics). To achieve her astronomic dream, Jocelyn Bell was intending to go to the Jodrell Bank Observatory at the
University of Manchester. Unfortunately, her application was lost by the staff of the
Jodrell Bank Observatory. And thus, she came to the University of Cambridge and
became Hewish’s postgraduate student. At Cambridge, she attended New Hall (now
Murray Edwards College) and worked together with Hewish’s team to construct the
Interplanetary Scintillation Array. This radio telescope was completed finally in July
1967 and soon carried out the observations to the sky survey. At that time, Jocelyn
Bell’s research direction was on the observation of interplanetary scintillation, and her
doctoral dissertation title is “The Measurement of Radio Source Diameters Using a
Diffraction Method”. According to the observation plan, Jocelyn Bell would sequentially observe a batch of radio sources, she repeated observation once each week,
and the recording paper tape of every day was 30 m long. The radio telescope was so
sensitive that both radio source signals and interference ones from the background
were recorded together. It was one of Jocelyn Bell’s tasks to identify the radio sources
from the interference signals every day. In repeating observation once every week,
the radio source signals always appeared in the same direction every time, while the
interference signals were random. Obviously, the same area in the sky was searched
and surveyed so repeatedly that the probability to discover the pulsar was increased
correspondingly.
In the solar system, the non-homogeneity of interstellar medium is resulted from
the solar wind. At night, since the observatory is always on the back to the Sun, it
is little impacted from the Sun, and hence the stronger interplanetary scintillation
is not observed generally. However, Jocelyn Bell surprisedly found that a series of
periodic “scintillation sources” with different intensities occurred in the direction
known non-existent radio sources, when she investigated the observation data at
night on August 6, 1967. During one-month observation, these scintillation signals
were always flickering appearance and all occurred at the same sidereal time. In
other words, the signals go through the meridian circle once every 23 h and 56 min,
which is just the period of the Earth’s rotation. After excluding the possibility of
being affected by the Sun and the interference from the Earth, it was shown that the
signal might come from a certain celestial object outside the solar system. And then,
Jocelyn Bell reported the observed phenomenon to her supervisor Professor Hewish.
In order to further observe the unusual scintillation source, Hewish’s research
team installed again a dedicated receiver with higher time resolution on November
28, 1967. It was shown from the observation results that the radio signals emitted
7
1.2.2 Discovery of Pulsating Radio Sources
In 1965, Professor Hewish recruited a female doctoral graduate student, Susan
Jocelyn Bell (now Professor Bell-Burnell, 1943−). Jocelyn Bell was born in Lurgan
town in County Armagh, Northern Ireland. Her father was an architect who had
helped design the Armagh Planetarium, and during visits, she was encouraged by
the staff to pursue astronomy professionally. Young Jocelyn also found her father’s
books on astronomy. She graduated from the University of Glasgow in 1965, with
a Bachelor of Science Degree in natural philosophy (Physics). To achieve her astronomic dream, Jocelyn Bell was intending to go to the Jodrell Bank Observatory at the
University of Manchester. Unfortunately, her application was lost by the staff of the
Jodrell Bank Observatory. And thus, she came to the University of Cambridge and
became Hewish’s postgraduate student. At Cambridge, she attended New Hall (now
Murray Edwards College) and worked together with Hewish’s team to construct the
Interplanetary Scintillation Array. This radio telescope was completed finally in July
1967 and soon carried out the observations to the sky survey. At that time, Jocelyn
Bell’s research direction was on the observation of interplanetary scintillation, and her
doctoral dissertation title is “The Measurement of Radio Source Diameters Using a
Diffraction Method”. According to the observation plan, Jocelyn Bell would sequentially observe a batch of radio sources, she repeated observation once each week,
and the recording paper tape of every day was 30 m long. The radio telescope was so
sensitive that both radio source signals and interference ones from the background
were recorded together. It was one of Jocelyn Bell’s tasks to identify the radio sources
from the interference signals every day. In repeating observation once every week,
the radio source signals always appeared in the same direction every time, while the
interference signals were random. Obviously, the same area in the sky was searched
and surveyed so repeatedly that the probability to discover the pulsar was increased
correspondingly.
In the solar system, the non-homogeneity of interstellar medium is resulted from
the solar wind. At night, since the observatory is always on the back to the Sun, it
is little impacted from the Sun, and hence the stronger interplanetary scintillation
is not observed generally. However, Jocelyn Bell surprisedly found that a series of
periodic “scintillation sources” with different intensities occurred in the direction
known non-existent radio sources, when she investigated the observation data at
night on August 6, 1967. During one-month observation, these scintillation signals
were always flickering appearance and all occurred at the same sidereal time. In
other words, the signals go through the meridian circle once every 23 h and 56 min,
which is just the period of the Earth’s rotation. After excluding the possibility of
being affected by the Sun and the interference from the Earth, it was shown that the
signal might come from a certain celestial object outside the solar system. And then,
Jocelyn Bell reported the observed phenomenon to her supervisor Professor Hewish.
In order to further observe the unusual scintillation source, Hewish’s research
team installed again a dedicated receiver with higher time resolution on November
28, 1967. It was shown from the observation results that the radio signals emitted