Jocelyn Bell Burnell University of Oxford Astrophysics And Mansfield College 1957 2 3 Crab PSR almost discovered I Late summer 1957 an Open Night at McDonald 82 inch Struve telescope ID: 267151
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Slide1
1
Reflections on the discovery of pulsars (pulsating radio stars)
Jocelyn Bell BurnellUniversity of Oxford Astrophysics AndMansfield CollegeSlide2
1957
2Slide3
3
Crab PSR almost discovered I
Late summer 1957; an Open Night at McDonald; 82 inch (Struve) telescope trained on Minkowski’s star. Elliott Moore (newly graduated from Chicago) was assisting.Female visitor –
‘That star’s flashing’No instruments existed to provide follow-up.Slide4
1966
4Slide5
5
PSR 0329+54 almost discovered
January 1966
408 MHz survey (Europe)
using
large telescopes
Last week of observing;
one
pen-recorder misbehaving
Early hours of morning, that pen recorder started
‘misbehaving’
Observer said ‘Damn!’ and thumped pen recorder – behaviour stopped!Slide6
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PSR0329 +54 contd
Observer said 'Good!', put on his coat and went home!........ He had made the
first
observation of PSR 0329+54
.
No entry in log book
Following
the discovery of the first pulsars (which did not include 0329+54)
no
search
of their
data for pulsars.Slide7
Oct/Nov 1967
7Slide8
Crab PSR almost discovered II
Sue
Simkin (NRAO) – Oct/Nov 1967
Carnegie Image Spectrograph,
Kitt
Peak 84-inch telescope.
Lo
Woltjer
asked her to take a spectrum of
Minkowski's
star.
Spectrum dull, but Sue observed flickering, or as if there were waves going out from it
.
LW
said it couldn't be, but when PSR discovered said it must have been
.Slide9
1967 - 8Slide10
Crab Pulsar – almost - III
E-mail message received by ATNF, June 2007 from Charles
Schisler: “As a USAF technician during a one year period back in 1967-68 at a Ballistic Missile Early Warning Site in Alaska I discovered fourteen pulsing signals on our extremely powerful radars….”Slide11
Crab Pulsar – almost - II
Not related to our mission my Air Force supervisors did not appreciate the possible scientific implications of my discovery. And the highly classified nature of our work made it impossible for me to publish, etc…..
contdSlide12
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Crab Pulsar contd….
“At the time I carefully made notes and their approximate location by RA and Dec. Ten or eleven of them have been identified as being pulsars as I have just discovered from the ATNF catalogue of 1771 pulsars. It is possible that all of them were pulsars. The first one that I discovered back in 1967 was the Crab Nebula and may have been the first pulsar ever noted by anyone……I am now 81 years OLD but I am still curious about a very exciting thing that happened to me forty years ago!” Slide13
1967 - 8
The actual discovery
13Slide14
14
First build your radio telescope
(through hail, rain and sunshine)
2048 81.5MHz
λ
/2 antennae (16 E-W rows of 64 + 64),
1000+ wooden posts, 120
miles/192 km wire
and cable,
area 57 tennis courts. Grant £12k. 6 people for 2 years.
Typical working conditions
for a PhD
student?Slide15
The 4.5 acre
*
radio telescope(*1.8 hectares), looking W
Interferometric array; phased with delay cables; operated with 4 beams. Valve phase-switching receiver!Slide16
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The programme
Using interplanetary scintillation to identify quasars (and measure their angular diameter)
Short time constant (short integration time) essential – IPS produces a rapidly fluctuating signal. τ
= 0.1 s.
6 months’ observing, starting July 1967Slide17
Data analysis
No
computer!3-pen chart paper100’ (30m) / day400’ (120m)/sky scan3.3 miles (5.3km) totalSlide18
Discovery of pulsars II
Occasionally
¼” (0.5 cm) in the 400’ (120 m) showed an unusual signal.
‘Occasionally’ = 15% of the occasions that part of sky observed
Slide19
High-speed recording
Centre trace shows pulsed nature of emissionSlide20
The naming of pulsars
Interviewed by Science Correspondent of The Daily Telegraph – Anthony Michaelis
– shortly after the discoveryWhat were we going to call them?He suggested pulsar – cf quasar
20Slide21
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Why then?
Pulsars, quasars, CMB, molecules, masers…..Slide22
Possible factors
Computers? No – arriving but not yet arrivedTransistors? No – arriving but not yet arrivedPost WWII technology kicking in? – Unlikely – it’s two decades since the end of the war.
Space race, drawing attention to astro?Critical mass of radio astronomers?22Slide23
Possible factors
Computers? No – arriving but not yet arrivedTransistors? No – arriving but not yet arrivedPost WWII technology kicking in? – Unlikely – it’s two decades since the end of the war.
Space race, drawing attention to astro?Critical mass of radio astronomers?23Slide24
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Key factors in the discovery
Our own telescope and receiver – I understood its
behaviour. One of the first observations with a short time constant (new area of phase space
).
As a research student I had time/space to follow-up anomalies.
‘Imposter syndrome’.Slide25
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Key factors,
contd
If we had computerised the search, would the pulsars have been discovered?We had a good address – a reputable laboratory
.
Essential for getting published!Slide26
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The End