Astrofest 2014 – Session 4

The final session of this year’s Astrofest started with a talk from Rob McNaught on Great Comets of the last 50 years. Rob works at the Siding Spring Observatory in Australia and has discovered 82 comets and over 50 supernovae to date as well as taking the first image of supernova 1987A.

Rob laid out his criteria for a great comet. In his view it should be big and bright with a big, bright tail. Using these criteria he went on to list what he thinks of as the 7 comets of the past 50 years which meet these criteria. It is impossible to do justice to Rob’s talk without showing the photos of these comets which gave the talk its real impact. Instead I will simply list the comets and urge you to go look for the images yourself on the internet. Comet Halley got a mention but does not make it into the final list. So in reverse order here are Rob’s great comets:

  • Comet West 1976
  • Comet Hale-Bopp 1997
  • Comet Heyakutake 1996
  • Comet Bennett 1970
  • Comet Lovejoy 2011
  • Comet McNaught 2007!! (he would wouldn’t he)
  • Comet Iyeka-Seki 1966 which is the only comet on the list he did not personally see.
The next talk from Lucie Green of the Mullard Space Science Laboratory dealt with Solar Maximum which is particularly timely as speculation about the Sun’s activity has been on the increase as a result of the lower levels of activity during the current solar cycle.
In her talk Lucie Green was at pains to emphasise that the solar cycle is not really a steady cycle as it varies from 8 to 15 years with a mean period of 11.1 years. However insofar as it can be considered a cycle it it a magnetic cycle with magnetic activity rising and falling with the number of sunspots. This is hardly surprising since sunspots are essentially a magnetic activity.
Predictions for the current sunspot cycle have proved to be well off the mark with the Sun being even less active in this cycle than even the most pessimistic predictions. So what is the prognosis for the next cycle. The indications are not good. It is widely thought that magnetic activity at the solar poles at the start of the solar cycle is closely linked to the strength of the cycle and the number of sunspots and CME’s it will produce. 
Having just passed solar maximum polar magnetic activity is at a very low level historically speaking which seems to indicate that the Sun is heading into one of its minima period. At least this is what Lucie Green is hoping for since, with a whole fleet of spacecraft already in place, it will allow study of the Sun in a state it has not been in for over 150 years since the Dalton minima of the 1860’s and may enable to explain what it is that causes these periods of minimum activity.
This was an excellent talk on a very topical subject.
The final talk of this Astrofest was given by Chris Lintott from the University of Oxford. It attempted to answer the question “Is the Milky Way Special?” Chris gave a very entertaining talk which compared the Milky Way galaxy to other galaxies in a number of ways.
  • What does it look like in comparison to other galaxies?
  • How did it grow and evolve?
  • Does it now or did it in the past have an active galactic nucleus and, more speculatively
  • how will it develop in the future
The outcome of all this, Chris says, is that the Milky Way is a fairly ordinary suburban galaxy. We live, it appears, in the galactic equivalent of Croydon.
And, on that depressing note, Astrofest 2014 is over and done with. It has been a great weekend and I hope you have got something useful from these brief reports.
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