The Journal of the British Astronomical Association

Volume 123, No.2: 2013 April

Summary contents page

Detailed contents: Notes and News / Articles / Observers' Forum / Reviews / Letters / Meetings / BAA Update

On the cover: The day of the asteroids!

Two small Near Earth Asteroids visited the Earth’s neighbourhood on the same day in 2013 February. Richard Miles describes this unique event in Notes & News below.

Notes and News

From the President (Bill Leatherbarrow) / 2013 February 15: The day of the asteroids (Richard Miles) / Aurora Section (Ken Kennedy & Dave Gavine) / Your new Deep Sky Section Director (Callum Potter) / Solar Section (Lyn Smith) / Stargazing Live 2013: in Regent’s Park (David Arditti) and at New Lanark Mills (Lyn Smith) / Recent observations of Mercury (Richard McKim) / The BAA and the European Planetary Science Congress 2013 (David Arditti)

Refereed papers

Building a large Dobsonian telescope ... Andrew Robertson

The design and construction of a 600mm Dobsonian-mounted Newtonian telescope is described.

John Ellard Gore: ‘Of immensity and minuteness’ ... Jeremy Shears

John Ellard Gore FRAS, MRIA (1845-1910) was an Irish amateur astronomer and prolific author of popular astronomy books. His main observational interest was variable stars, of which he discovered several, and he served as the first Director of the BAA Variable Star Section. He was also interested in binary stars, leading him to calculate the orbital elements of many such systems. He demonstrated that the companion of Sirius, thought by many to be a dark body, was in fact self luminous. In doing so he provided the first indication of the immense density of what later became known as white dwarfs.

Investigating the properties of the near-contact binary system TW CrB ... D. Pulley, G. Faillace, C. Owen & D. Smith

TW Coronae Borealis (TW CrB) is a binary system likely to be active, showing evidence of starspots and a hotspot. We calculated a new ephemeris based on all available timings from 1946 and find the period to be 0.58887492(2) days. Based on lightcurve simulation analysis we conclude that the two stars are close to filling their Roche lobes, or possibly that one of the stars’ Roche lobe has been filled. The modelling also led to a hotspot and two starspots being identified. Conservative mass transfer is one of a number of possible mechanisms considered that could explain the change in period, but the mass transfer rate would be significantly lower than previous estimates. We found evidence that suggests the period was changing in a cyclical manner, but we do not have sufficient data to make a judgement on the mechanism causing this variation. The existence of a hotspot suggests mass transfer with a corresponding increase in the amplitude in the B band as compared with the R and V bands. The chromospheric activity implied by the starspots makes this binary a very likely X-ray source.

The BAA VSS Long Term Polar Monitoring Programme: the first five years, 2006-2011 ... Gary Poyner

A programme of observation to monitor the long term optical behaviour of a small group of magnetic cataclysmic variable stars (Polars) has been set up and run by the Variable Star Section of the British Astronomical Association. Here we present the results of the first five years of our study - 2006 to 2011 - in the form of lightcurves for 17 of the 18 objects on the programme.

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  • Observing the Solar System: The modern astronomer’s guide by Gerald North,
    Cambridge University Press, 2012. ISBN 978-0-521-89751-8. Pp xvi + 489, £30 (hbk).
    Reviewed by John Chuter
  • Are we being watched? : The search for life in the cosmos by Paul Murdin,
    Thames & Hudson, 2013. ISBN 978-0-500-516713. Pp 224, £16.95 (hbk).
    Reviewed by Roger O’Brien

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    Observers’ Forum

    The 'Leo Triplet' of galaxies imaged by Keith Grice

    The night sky for April & May: Sky notes ... by Brian Mills

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