The Oxford Science Lecture Series
Professor Katherine Blundell
University of Oxford
“Black Holes and spinoffs”
Dorothy Hodgkin Memorial Lecture 2019
University Museum, Oxford, 6th March 2019
Katherine Blundell is Professor of Astrophysics at the University of Oxford and a Research Fellow at St John’s College. She started her academic career with a Junior Research Fellowship at Balliol College, followed by a Fellowship from the Royal Commission for the Exhibition of 1851 and then a prestigious University Research Fellowship from the Royal Society.
Professor Blundell began her lecture by discussing the work of Dorothy Hodgkin, saying that her research was truly international. She said that in parallel with her work to elucidate structures of molecules using X-rays, which of course led to her being awarded the Nobel Prize, she also used her international contacts to promote peace and to ‘persuade people to be better’.
Professor Blundell showed us a view of the sky on a clear night, saying that the human eye is good at seeing the night sky but is limited by distance. With a digital camera one can detect galaxies, as you have increased the ‘collecting area’ of vision from the retina to the lens. If you scale up further to a telescope you can detect stars and the conglomerates of gas that will become stars. If you look towards Cygnus, using white light, you can zoom in on a giant galaxy but to get information about what is going on in there you need to use radio waves. In that way you can detect a dot at the centre of the galaxy with two jets leading away in opposite directions, 100,000 light years across from end to end, which have taken one million years to form. [Professor Blundell commented at this point that although studying biology is complex, biologist have it easy in comparison to astronomers because changes in biological systems happen over a short period of time in comparison to the changes in structures of stars and galaxies!]
The dot at the centre of the galaxy is a black hole and the extragalactic quaser jets can be found all over the universe, but how is this material able to escape from the pull of gravity from a black hole? Professor Blundell explained that this occurred because of the law of conservation of angular momentum. As material goes into a black hole it enters a vortex, spiralling down towards the centre. However some material is spat out, in opposite directions, tracing out a cone due to the rotation of the black hole. In order to study this phenomenon, it is necessary to monitor a black hole consistently over six months, but clearly this is not possible as other people also need to use the telescopes! Professor Blundell described how she used more easily available instruments to measure optical radiation from the sky and looked at hydrogen spectra from the black hole. Due to the Doppler effect, if the hydrogen atoms are moving in different directions, one would expect to see a shift in the optical radiation to either side of that from stationary hydrogen atoms. She wanted to use this to study the material attracted to and expelled from black holes over time so she set up a project called ‘Global Jet Watch’. Optical astronomy can only be done in darkness so she established telescopes with an imaging camera and a spectrograph in five locations around the world: South Africa, Chile, either end of Australia and India. With help from the company Sophos she has linked the data from all these stations so that the same region of space can be monitored continually.
Professor Blundell went on to explain that each telescope has been installed in a residential school and that the pupils at the schools can also use the telescopes. As darkness falls in each region the children can use the telescopes until their local bedtime, at which time control switches to Oxford. This is inspiring the children not to be afraid of using scientific technology.
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