Astronomy in Darkness

Yesterday, being the second Friday of the month, was the day for the Ordinary Meeting of the Royal Astronomical Society (followed by dinner at the Athenaeum for members of the RAS Club). Living and working in Cardiff it’s difficult for me to get the specialist RAS Meetings earlier in the day, but if I get myself sufficiently organized I can usually get to Burlington House in time for the 4pm start of the Ordinary Meeting, which is open to the public.

The distressing news we learnt on Thursday about the events of Wednesday night cast a shadow over the proceedings. Given that I was going to dinner afterwards, for which a jacket and tie are obligatory, I went through my collection of (rarely worn) ties, and decided that a black one would be appropriate. When I arrived at Burlington House I was just in time to hear a warm tribute paid by a clearly upset Professor Roger Davies, President of the RAS and Oxford colleague of the late Steve Rawlings. There then followed a minute’s silence in his memory.

The principal reaction to this news amongst the astronomers present was one of disbelief and/or incomprehension. Some  friends and colleagues of Steve clearly knew much more about what had happened than has so far appeared in the press, but I don’t think it’s appropriate for me to make these public at this stage. We will know the facts soon enough. A colleague also pointed out to me that Steve had spent most of his recent working life as a central figure in the project to build the Square Kilometre Array, which will be the world’s largest radio telescope. He has died just a matter of days before the announcement will be made of where the SKA will actually be built. It’s sobering to think that one can spend so many years working on a project, only for something wholly unforeseen to prevent one seeing it through to completion.

Anyway, the meeting included an interesting talk by Tom Kitching of the University of Edinburgh who talked about recent results from the Canada-France-Hawaii Telescope Lensing Survey (CHFTLenS). The same project was the subject of a press release because the results were presented earlier in the week at the American Astronomical Society meeting in Austin, Texas. I haven’t got time to go into the technicalities of this study – which exploits the phenomenon of weak gravitational lensing to reconstruct the distribution of unseen (dark) matter in the Universe through its gravitational effect on light from background sources – but Tom Kitching actually contributed a guest post to this blog some time ago which will give you some background.

In the talk he presented one of the first dark matter maps obtained from this survey, in which the bright colours represent regions of high dark matter density

Getting maps like this is no easy process, so this is mightily impressive work, but what struck me is that it doesn’t look very filamentary. In other words, the dark matter appears to reside predominantly in isolated blobs with not much hint of the complicated network of filaments we call the Cosmic Web. That’s a very subjective judgement, of course, and it will be necessary to study the properties of maps like this in considerable detail in order to see whether they really match the predictions of cosmological theory.

After the meeting, and a glass of wine in Burlington House, I toddled off to the Athenaeum for an extremely nice dinner. It being the Parish meeting of the RAS Club, afterwards we went through a number of items of Club business, including the election of four new members.

Life  goes on, as does astronomy, even in darkness.

3 Responses to “Astronomy in Darkness”

  1. So fascinating to hear from inside one of the RAS meetings.

    Forgive me if I’m a bit behind the times–are the postulated reasons for differences in dark matter distribution the same as those for the distribution of normal matter? Quantum ripples and inflation and such? I was just reading up on this explanation and I’m interested in hearing competing theories.

  2. How filamentary it appears depends on where the contour levels are set (in a contour plot) or, as here, how the colour scale is defined. Plots like this should have a scale showing which colour corresponds to which value.

    I sometimes have the impression that some of Arp’s contour plots might be somewhat tweaked so that they make things look more filamentary than they otherwise would.

    • telescoper Says:

      To be fair, the picture Tom showed did have a colour scale; that one above is just a PR image. The real point however is that it is necessary to analyse such images carefully in order to quantify the pattern objectively rather than relying on eyeball impressions.

      The CHFTLens website has more detailed information:

      http://www.cfhtlens.org/

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