Meeting Report from Monday 5th February 2018
Simon White updated the meeting with the latest news on our developing schedule of events for the year, followed by the Sky Notes for the coming month.
David Glass presented news from the cutting edge.
In addition to the two red giant stars for which surfaces have been imaged, Antares and Betelgeuse:
An asymptotic giant branch (AGB) red giant star has now been imaged:
Red Giant ∏1Gruise
All three images large-scale structures which are giant convection cells – and only a few of them per star, compared to the Sun which has millions. One of the stars was clearly non-spherical and was distorted with a large bulge visible on one side.
The Mars rover called Opportunity passes by the notice of the media as it trundles around on Mars sending back data. It is now ’14 years into its 90-day mission’
David also let us know about the Dark Skies Festival coming to the People’s Hall, Sedbergh on Monday 19th February Photographing the Dark Skies above Sedbergh. and a talk two days later.
Constellation of the month
Moira Greenhalgh gave an illustrated talk on the winter constellation, Taurus (the bull) rising after Perseus and before Orion.
The association of the constellation with a bull precedes Classical civilisation – illustrated on Palaeolithic cave paintings such as at Lascaux.
The star cluster Pleiades (the Seven Sisters) was/is significant to indigenous peoples from Australia to the Americas.
Objects of other interest: the bright orange star Aldebaran, Hyades cluster, M1 Crab nebula, Taurus/Auriga complex of dust and gas, Gould’s Belt and not least, Kappa Tauri was the star chosen by Arthur Eddington to photo during the 1919 solar eclipse to prove the General Theory of Relativity
Supernovae and the Discovery of Dark Energy
Prof Isobel Hook gave an enlightening illustrated talk on the part played by Type 1A supernovae in galaxies to measure cosmological distances and the startling issues raised. The talk managed to seamlessly intersperse Cosmological theory and very practical measurements.
We know the Universe is expanding following The Big Bang. Prior to the 1990’s, everyone believed that the expansion of the Universe had only three different outcomes: it kept expanding forever, it eventually reached an asymptotic constant size getting there after an infinite
time, or it collapsed back to a point – the Big Crunch. In all cases, the expansion rate slowed down with time. But in the 90’s evidence was found through observation that the rate of expansion was increasing.
The cause of this acceleration in expansion is not understood but Dark Energy was explained early on as a place-holder name for unexplained, now increasingly observed phenomena of the ‘accelerating’ rate of universal expansion – despite the gravitational mass of the universe it will not only expand indefinitely but it will expand at an ever-increasing rate
Recent programmes with digital detection can now detect tens to hundreds of supernovae over a few searches whereas before the ’90s ten detections over a lifetime was the record. After detection, ground and space-based telescopes can measure the light from the supernova to determine their type, through their spectra, and the apparent magnitude, to infer distance and redshift of the containing galaxy to measure expansion since the light was emitted Red-shift was explained as not so much to do with a receding source (Dopler effect but simply the same wave over a stretched space as the Universe expanded. With new telescopes under construction, the number of supernovae detection per programme will increase by an order of magnitude. Isobel closed by describing the Extremely Large Telescope.
The Universe is going to be a lonely place. In this early stage, make the most of our neighbours.