Flamsteed Astronomy Society

‘The Magic of the Sun’ — Prof John Brown

November 6, 2006

Prof John Brown, Astronomer Royal for Scotland, talked to us in the Great Hall, Queen’s House, about ‘the Magic of the Sun’.

John’s trademark is to use magic effects to illustrate his points and he didn’t disappoint.  His style may have been a little cramped because we were lucky enough to see him only 18 months earlier, and he was worried some of the tricks would be old.   But no fear!

Solar physics is John’s speciality and he organised his talk around a list of mysteries about the Sun, including —

·         Why is the corona so hot?  The ionised gas in the corona (the part visible during an eclipse) is at upwards of 1 million degrees but the Sun’s surface is only at 6000 degrees.  What keeps the corona so hot?  Apparently an effect called ‘ magnetic reconnection’ — or is it?

·         How can we explain the ‘ missing neutrinos’?  The Sun emits a huge stream of neutrinos — very light elementary particles with no electrical charge.  Billions stream through us and the Earth every second and they are very hard to detect.  In the best detectors buried deep underground in

·         How do we know what’s going on inside the Sun?  One way is by listening to the vibrations of the Sun, ‘sunquakes’, using helioseismology, in much the same way as geologists use seismology to listen to  the vibrations of the Earth during Earthquakes.

·         Is there a connection between sunspot activity and the weather on Earth?  Apparently so.  There is an inverse correlation between sunspots and cloud formation — when there are fewer spots, more clouds form.

During the talk John shared a wealth of anecdotes from his Sun-watching career.  He has only just managed to see a total eclipse, this year, in Turkey.  Sitting comfortably in a deckchair he took just 5 pictures with a handheld camera and produced an excellent layered image of the Corona.

He also told us about the RHESSI mission — a small satellite designed to record high-energy release from solar flares.  John worked on the mission and has kept two versions of the launch video: the official perfect launch, and an unofficial secret copy with unexpected shots not released by NASA!

The venue for John’s talk was the beautiful Great Hall in the Queen’s House NMM.  One of only a couple of rooms which are perfect cubes.  Visually stunning but the acoustics are abysmal.  We can only hope that the intense echo didn’t spoil the audience’s enjoyment too much

MRD

Canada, only very few neutrinos can be detected.  But we only count a third of the number predicted by our best theories of solar physics.  Why?  Seems like the neutrinos are changing between types (there are three) during their journey to our detectors and we only detect one of the three kinds.

·         Is it nuclear fusion that makes the Sun shine?  Seems not.   Photons of light created deep inside the Sun take 10 million years to stagger up to the Sun’s surface because of all their collisions with the particles of the ionised gas on the way.  If the fusion reactions were switched-off now, we wouldn’t notice much change for 10 million years.  Most of the energy for shining comes from the contraction of the Sun under the gravity of its enormous mass.  The energy from fusion serves to counteract some of the contraction and is extending the lifetime of the Sun.

The truth is out there!  A ghostly green glow envelopes the Astronomer Royal for Scotland .  Spooky  (pic: Ian McDowell)

Prof John Brown (pic Mike Dryland)

A demonstration of Helioseismology — Finola assists  (pics: Mike Dryland)

Is it the solar wind, or was it the baked-beans?  An impromptu demonstration in the bar   (pics: Mike Dryland)