Pulses and Pulsars – An introduction to time domain radio astronomy

Pulses and Pulsars – An introduction to time domain radio astronomy

Presented by Dame (Susan) Joycelyn Bell Burnell of the University of Oxford Astrophysics and Mansfield College. The presentation took place at the Stellenbosch Institute for Advanced Study’s (STIAS) Wallenberg Centre on the 19th of February 2014

I am always slightly apprehensive about attending talks by visiting academics of the stature of Dame Joycelyn Bell Burnell.  Perhaps this apprehension stems from a lack of confidence in my own understanding of the field they are going to cover in their talks.  There are also other possible issues like the quality of the presentation and how clearly the person will speak and, of course, the acoustics of the venue.  The STIAS venue does not have good acoustics and experience has taught me that academics of international repute do not necessarily speak clearly or have well laid out talks using clear and legible slides.  I had read that Jocelyn was a good presenter but, just to be safe, Lynnette and I made sure that we got seats close to the front (third row) and more or less on the centre line of the projection screen.

Jocelyn’s talk covered quite a lot of ground.  She touched briefly on her original discovery of the first three pulsars during her PhD-studies and then talked at length on the characteristics of pulsars.  She started off explaining how very high mass stars had short lives and eventually ended up as pulsars.  Dame Bell Burnell made mention of their enormous masses, all crammed into balls with 10 km radii resulting in incredibly high densities and really freakish gravitational and magnetic fields.  Jocelyn humorously sketched the possible consequences to humans if they should visit a pulsar and concluded that such a visit could definitely be injurious to one’s health and one’s credit card.  We were taken on a visit to the only known pulsar that has a planetary system associated with it and also introduced to the short lived world of the brief radio pulses that are currently puzzling radio astronomers.  Most of these reports originate from an Australian radio telescope and I was wondering whether Wombats or any of the other marsupials Down-Under squeak at around 700 Hz?

Lastly she looked at the SKA-project and briefly made mention of the greatly increased sensitivity the instrument would bring to the field of radio astronomy.  After her talk Jocelyn fielded a large number of questions on topics not always related to the subject of her presentation.

Jocelyn’s presentation was excellent at all levels.  Her ability to relate to and communicate with people was clearly demonstrated by the throngs of questioners that she patiently handled after the talk.  Her patience even extended to having her picture taken with members of the Cape Center of ASSA, including Lynnette and myself.

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Lynnette and Dame Joycelyn Bell Burnell with the SKA’s Bernie Fanaroff trying to avoid the camera.
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Edward and Dame Jocelyn Bell Burnell

 

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Carol, Dame Joycelyn Bell Burnell and Serena

Chameleon Star Baffles Astronomers

Pulsars are small stars, smaller than a large city but they are heavy stars, much heavier than our Sun and they spin very rapidly.  While spinning they emit two beams of high energy electromagnetic waves that flash across the sensors of a variety of scientific recording instruments, like the beam of a lighthouse across the sea. First discovered in 1967 by Jocelyn Bell, now Dame (Susan) Jocelyn Bell Burnell DBE, FRS, FRAS and her thesis supervisor Anthony Hewish, they are enigmatic but, up to know, scientists knew they did not understand the fine detail of how these stars operated, but they felt they had a good grip on the general system.

All that has now been changed by a small team working at the University of Amsterdam.  The team also included the University of Vermont’s Joanna Rankin (she has studied this pulsar, known as PSR B0943+10, for more than a decade), Wim Hermsen from SRON, (the Netherlands Institute for Space Research in Utrecht (the lead author on the new paper); Ben Stappers from the University of Manchester, UK; and Geoff Wright from Sussex University, UK.

To upset the pulsar apple cart they elicited the help of colleagues from institutions around the world to conduct simultaneous observations with the European Space Agency’s X-ray satellite (XMM-Newton), and two radio telescopes, the Giant Meter Wave Telescope (GMRT) (India) and the Low Frequency Array (LOFAR) (the Netherlands).

This pulsar was previously known to flip on and off every few hours alternating between bright (or strong) radio emissions and quiet (or weak) ones.  Using the combined instrumentation the researchers found, to their surprise, that this pulsar exhibited the same behaviour, but in reverse, when observed at X-ray wavelengths. .Flipping between these two extremes – one dominated by X-ray pulses, the other by a highly organized pattern of radio pulses – was completely unexpected, according to Rankin. Neither of the leading models for pulsar emission predicts, or in fact explains such behaviour.

These observations will probably keep theoretical astrophysicists busy investigating possible physical mechanisms that could cause the sudden and drastic changes to the pulsar’s entire magnetosphere and result in such a curious flip in its emissions.

Pulsar is a portmanteau of pulsating star.  To read more about this definition go here.

To read the rest of the article in ScienceDaily go here.