Gibbous Moon

A few nights ago I noticed a white spot on the terminator of the gibbous Moon (just above the middle of the left-hand edge).  I have noticed this before many times, and have always assumed that it was the bright patch around the crater Copernicus.  However, this time I decided to check this by taking a photo (hand-held, through an open window) and this was the result.  What it shows is that the white spot is not the area around Copernicus but the brightly sunlit inner wall of the crater.  I should really have known this, as the area around the crater only becomes bright when the sun is overhead.

Photo taken on 2010-10-17.

Mercury, Saturn and Venus

A photo taken out of our bedroom window at just before 7am this morning.  The bright object to the upper right is Venus (at magnitude -3.8) .  Mercury (mag -1.0) is about 60% of the way along the line from Venus to the satellite dish.  And, if you look carefully, you can just make out a faint Saturn (mag +1.1) to the lower left from Venus.  Saturn is unusually faint this year because the rings are almost edge-on.

Photo taken in Reading, UK, on 2009-10-12.

Direct Observations of the Orbit of Beta Lyrae

Somehow I missed this paper when it appeared on ArXiv this summer: Zhao et al, First Resolved Images of the Eclipsing and Interacting Binary Beta Lyrae, arXiv:0808.0932v1 [astro-ph], 2008.  The darker blob is the donor star, and the paler blob is the thick disk that surrounds the gainer star. 

Beta Lyrae is one of the longest and most intensively studied variable stars, but has only revealed its secrets very slowly.  The above paper provides the first direct evidence that the two components are ellipsoidal in shape.  It is interesting to see that the disk component seems flatter and fainter at phase 0.595 because there is a fairly persistent slight dip in this part of the orbital light curve.  It could be that the disk is more of an asymmetric spiral, or it could be that the brighter part of the fainter component is actually the hot-spot where the gas from the donor hits the disk.

Back when I was young, I used to make visual estimates of the brightness of Beta Lyrae and use these to derive fairly crude orbital light curves.

Eddingtoniana

Last Saturday I watched the BBC drama "Einstein and Eddington".  I will just say that the wonder isn't that it was done well, but that it was done at all.  For a program about such an abstruse subject (the 1919 Eclipse test of general relativity) to appear on television is pretty unusual; for it to involve such high profile actors as Andy Serkis ("Gollum") and David Tennant ("Doctor Who") seems little short of a miracle.  So, instead of grumping about the inaccuracies, I will just provide a few links to some background material:

A. S. Eddington, "Report on the Relativity Theory of Gravitation", The Physical Society of London, 1920. (Eddington's report on general relativity, which got a mention in the program.)

Daniel Kennefick, "Not only because of Theory: Eddington and the Competing Myths of the 1919 Eclipse Expedition", arXiv:0709.0685, 2007. (A thorough debunking of the rumours that Eddington fudged the results of the 1919 Eclipse Expedition.)

And, finally, that famous little story about Eddington (here told in Walter Grazer, "Eurekas and Euphorias: The Oxford Book of Scientific Anecdotes", Oxford, 2002):

Eddington was painfully shy but far from modest. His illustrious pupil Subramanyam Chandrasekhar recalled overhearing a conversation between Eddington and another astronomer, Ludwig Silberstein: Silberstein believed that he himself had a firm grasp of Einstein's theory and complimented Eddington for being one of the three people in the world to understand it.  When Eddington hesitated Silberstein asked why he was flaunting his false modesty.  'Not at all', came the reply, 'I am trying to think who the third one might be.'

Nova Cygni 1975

Thirty-three years ago, on the evening of 31st August 1975, I was out in my parent's back garden setting up my binocular tripod for a night of variable star observing.  The sky was just beginning to get dark and the brighter stars were visible.  As I was tightening various bolts on the tripod, I looked up and noticed a 2nd-magnitude star that shouldn't be there in the gap between Deneb and Cepheus.  My first thought was that it must be a satellite, and I fully expected that, within a few seconds, it would have moved relative to the background stars.  I looked down to concentrate on securing the bolts and then glanced up again.  The star hadn't moved.  I immediately realized it must be a nova.

This new star had actual been discovered by several observers in Japan two days earlier, on the 29th of August, when it was magnitude 3.  Many other people around the world saw it on the the 30th when it had reached magnitude 1.8.  Unfortunately I had been clouded out on that night, and by the time I saw it, it was already fading.  The star was a distinct yellow colour when I first saw it, which suggested to me that it was already on the decline; novae are normally white or even bluish at or before maximum.  Over the following weeks, the star became distinctly red as it faded.

I continued to observe the nova whenever I could through to February of the following year. By then it had faded to magnitude 9.8.  The above light-curve (a plot of magnitude against Julian Day number) shows my results.  The very rapid early decline suggests that this was one of the most intrinsically luminous novae on record.