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of signals observed. Instead, it
could be emitting a steady radio
signal in a beam that it swept
around in circles, just like a beam
of light from a lighthouse. When the
pulsar’s beam (or perhaps one of its
two beams) was pointing at Earth,
a signal would be detected, which
would show up as the sort of short
pulse that Bell had noticed on
printouts. When the beam had
passed by Earth, the signal would
stop until the beam came around
again. Challenged about the
pulsation rates, which implied
extremely rapid spinning, Gold
explained that neutron stars could
be expected to behave in this way
because of the way in which they
form—from the collapse of stellar
cores in supernova explosions.
Confirming the hypothesis
Initially, Gold’s explanations were
not well received by the astronomy
community. However, they became
widely accepted after the discovery
of a pulsar in the Crab nebula, a
well-known supernova remnant.
Over subsequent years, many more
NEW WINDOWS ON THE UNIVERSE
pulsars were found. They are
now known to be rapidly rotating
neutron stars with intense
electromagnetic fields, which emit
beams of electromagnetic radiation
from their north and south poles.
These beams are often, but not
always, radio waves and sometimes
other forms of radiation, including
in some cases visible light. One
reason for the excitement regarding
the discovery of pulsars was that
it increased the likelihood that
another theoretical phenomenon—
black holes—might also be
detected and proven. Like neutron
stars, black holes are objects that
could result from the gravitational
collapse of a stellar core following
a supernova explosion.
In 1974, Hewish and Martin Ryle
shared a Nobel Prize: “Ryle for his
observations and inventions ... and
Hewish for his decisive role in the
discovery of pulsars.” However,
Jocelyn Bell Burnell was told that
she would not share the award with
them because she had still been a
student at the time of her work. She
graciously accepted that decision. ■Jocelyn Bell Burnell
Jocelyn Bell was born in 1943
in Belfast, Northern Ireland.
After earning a physics degree
from Glasgow University in
1965, she moved to Cambridge
University, where she studied
for a Ph.D. There, she joined
the team that built a radio
telescope to detect quasars. In
1968, Bell became a research
fellow at the University of
Southampton and changed
her last name to Bell Burnell
when she married. She has
held astronomy and physics-
related positions in London,
Edinburgh, and at the Open
University, where, from 1991
to 2001, she was professor of
physics. From 2008 to 2010,
she was President of the
Institute of Physics. Bell
Burnell has received numerous
awards for her professional
contributions, including the
Herschel Medal of the Royal
Astronomical Society in 1989.
In 2016, she was visiting
professor of astrophysics
at Oxford University.Key work1968 Observation of a Rapidly
Pulsating Radio Source (with
Antony Hewish and others)Rotating
neutron starBeam aligned
with EarthBeam not aligned with Earthoff on off
TIMESIGNALA spinning neutron star that is emitting radiation beams can be detected
as a pulsar on Earth if, as it spins, one or possibly both of its radiation beams
recurrently point in Earth’s direction as they are swept around through space.
The pulsar will then be detected as a very regular series of signal “blips.”