Flamsteed Astronomy Society

Monday December 6, 2004 — Fifty or so members and their guests gathered in the Lecture Theatre to listen to Guy Hurst's talk on The Search for Novae and Supernovae.   Besides editing The Astronomer magazine Guy is Vice President of the BAA and coordinator of the UK Novae and Supernovae Sky Patrol.   The Sky Patrol is a group of amateur astronomers and Guy told us about their work.   He began by describing the nature of novae and supernovae and a brief history of their observation.   Novae are binary stars that suddenly grow bright when gas from one is transferred to a companion white dwarf, leading to a thermonuclear runaway.   Much of the envelope is ejected from the system but the star survives.   A supernova is a violent explosion of a star, binary or otherwise.   In a supernova the star is destroyed.   These latter 'guest stars' have been observed throughout history.

In 1006 a supernova in Lupus was so bright it cast shadows and could be seen in daylight. It is believed to have had a magnitude of -9. (Venus, at -4 magnitude, is just possible to see in daylight).   It is the brightest star ever recorded.   Another was seen in 1054 in Taurus with a magnitude near -4.   Its remnant is M1, the Crab Nebula.   Tycho Brahe observed a supernova in 1572 and Kepler in 1604.   More recent supernovae have been observed at lower magnitudes in 1892 (+4.2) and 1901 (+0.2).  Thomas Anderson observed this latest one at Mt Palomar.



Guy Hurst on The Search for Novae & Supernovae — from visual to laptop

In 1972, in The Astronomer, Jim Muirden suggested keeping a photographic record of the night sky, and as a result the Sky Patrol was started in 1973.   Muirden devised a light box to compare photographs, taken with a 50mm lens and HP4 film, and in this way in 1974 discovered a nova, which was later confirmed.   (His light box is still in working order right down to the original 25 watt light  bulbs!).

In 1976 a nova search programme was launched by John Hosty, when all negatives of the Sky Patrol were checked.   The patrol is very much the work of amateurs.   John Hosty himself patrolled every clear night, all night, with a broken pair of 10x50 binoculars — in effect a monocular.   In this programme the sky was divided up into zones and allocated to members.   The Milky Way comprised 121 zones.   The need for two exposures was vital to eliminate spurious images, and results checked against a master.   In 1977 Hosty found a nova in Sagitta which was confirmed two days later.   This was a major contribution and made by an amateur.   The group liaises with professional astronomers and discoveries are immediately notified through the clearing house at the “Central Bureau of Astronomical Telegrams”   Following on from John Hosty, Robert McNaught, in Australia, in 1986 sighted a nova in Centaurus, and then two others.  Next came Dave McAdam in 1989.   Then in 2001 Mike Collins found a nova that had been missed by the professionals.   In 2003 a patrol member found a nova in M31.


Looking for supernovae in other galaxies requires a telescope.   In 1991 a member in Italy had such a success, and in 1996, Mark Armstrong, a member in Kent, was the first English person to find a supernova.   Searching for supernovae in other galaxies can be frustrated by asteroids lurking close by — very often misidentified as a supernova, but then again, a supernova can outshine its whole galaxy.   By 2003, 100 novae had been discovered by patrol members in the UK.   The UK does exceptionally well in this field.   By 2004 168 supernovae had been discovered in other galaxies.   Members also monitor the progress of these events by recording their light curves, both in white light and colours, plotting brightness over time.   Most novae and supernovae simply fade, but rare “dusty” novae quickly fade and then slightly recover. There are also erratics that undulate.   Currently Guy is plotting a non standard nova that has faded, then plateaued before resuming its fall.

The latest addition in the progress of technology, from naked eye, through binocular, to telescope observation, is the Charge Coupled Device (CCD) which is more sensitive than film emulsion.  The CCD is attached to a camera and the image converted to digital form before being fed into a computer.   This up to date method is quicker, more reliable and requires a shorter exposure than film.


Guy concluded by inviting new members to come forward as more patrollers are needed.   You only need a pair of 10x50 binoculars. His e mail address is  —   guy@tahq.demon.co.uk

In questions Guy said patrolling was possible in London.   He also said no supernova in the Milky Way has been studied with a telescope. Reassuringly, he said the sun wasn't going to suddenly blow up!   If it does, we’ll be very cross with him.


Frank Bath & Ian McDowell


Photos Ian McDowell