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15 Radio Astronomy
seen as an isotropic microwave signal. Dicke even went as far as to suggest that the
Bell Labs Horn antenna must be the perfect instrument to detect the signal. This was
the very signal detected by Penzias and Wilson—the cosmic microwave background
(CMB).
Penzias and Wilson were awarded the 1978 Nobel Prize in Physics for the discovery of the CMB. When you look at a detuned terrestrial television, about 1% of
the signal you see is from the CMB. You are seeing the birth cry of the universe on
your television.
A few years after Penzias and Wilson’s discovery, a young graduate astronomer,
Jocelyn Bell Burnell, was working on a dipole radio telescope in Cambridge, England, known as the hop field, due to its similarity to the supports used for growing
hops.
Bell Burnell noticed a strange signal in her data. It was astronomical, strong and
varying very rapidly and with a very consistent period. Initial fears that the signal
was of alien origin were soon put aside when it was realised that Bell Burnell had
detected the first pulsar, a dense rotating neutron star emitting two tight beams of
radio waves that briefly become visible to the observer as the star rotates, very much
in the manner of a lighthouse. Neutron stars are formed in explosions of supernovae,
and this object was located in the heart of the Crab Nebula.
Bell Burnell’s doctoral supervisors were awarded the Nobel Prize in Physics for
Bell Burnell’s discovery, though Bell Burnell was not, somewhat controversially.
Bell Burnell is on record as stating that she believes that this was the right choice
and that her supervisors were fundamentally responsible for the project. However,
Bell Burnell has gone on to be a very successful and well-respected astrophysicist
and is a strong advocate for the involvement of women in science.
Radio astronomy has become increasingly attractive to astrophysicists, as it can
operate in daylight and most weathers (depending on frequency), is mostly unaffected
by interstellar reddening, and can observe both high- and low-energy phenomena that
are not accessible by conventional optical and infrared observations.
The principal limitations of radio astronomy are its general insensitivity and poor
resolution. However, the facility with which multiple radio telescopes may be combined in an array, together synthesising a single large virtual telescope, of diameter
equal to the greatest separation between component telescopes of the array (interferometry), have overcome these obstacles.
In the coming years, three very large interferometers will reach full operation.
Both ALMA, a very large submillimetre interferometer, and LOFAR, a very large
long-wave interferometer, are now operating. Work is about to start in South Africa
and Australia on the Square Kilometre Array, and its completion will usher in a new
era of radio astronomy.
15 Radio Astronomy
seen as an isotropic microwave signal. Dicke even went as far as to suggest that the
Bell Labs Horn antenna must be the perfect instrument to detect the signal. This was
the very signal detected by Penzias and Wilson—the cosmic microwave background
(CMB).
Penzias and Wilson were awarded the 1978 Nobel Prize in Physics for the discovery of the CMB. When you look at a detuned terrestrial television, about 1% of
the signal you see is from the CMB. You are seeing the birth cry of the universe on
your television.
A few years after Penzias and Wilson’s discovery, a young graduate astronomer,
Jocelyn Bell Burnell, was working on a dipole radio telescope in Cambridge, England, known as the hop field, due to its similarity to the supports used for growing
hops.
Bell Burnell noticed a strange signal in her data. It was astronomical, strong and
varying very rapidly and with a very consistent period. Initial fears that the signal
was of alien origin were soon put aside when it was realised that Bell Burnell had
detected the first pulsar, a dense rotating neutron star emitting two tight beams of
radio waves that briefly become visible to the observer as the star rotates, very much
in the manner of a lighthouse. Neutron stars are formed in explosions of supernovae,
and this object was located in the heart of the Crab Nebula.
Bell Burnell’s doctoral supervisors were awarded the Nobel Prize in Physics for
Bell Burnell’s discovery, though Bell Burnell was not, somewhat controversially.
Bell Burnell is on record as stating that she believes that this was the right choice
and that her supervisors were fundamentally responsible for the project. However,
Bell Burnell has gone on to be a very successful and well-respected astrophysicist
and is a strong advocate for the involvement of women in science.
Radio astronomy has become increasingly attractive to astrophysicists, as it can
operate in daylight and most weathers (depending on frequency), is mostly unaffected
by interstellar reddening, and can observe both high- and low-energy phenomena that
are not accessible by conventional optical and infrared observations.
The principal limitations of radio astronomy are its general insensitivity and poor
resolution. However, the facility with which multiple radio telescopes may be combined in an array, together synthesising a single large virtual telescope, of diameter
equal to the greatest separation between component telescopes of the array (interferometry), have overcome these obstacles.
In the coming years, three very large interferometers will reach full operation.
Both ALMA, a very large submillimetre interferometer, and LOFAR, a very large
long-wave interferometer, are now operating. Work is about to start in South Africa
and Australia on the Square Kilometre Array, and its completion will usher in a new
era of radio astronomy.