Archive for the The Universe and Stuff Category

RIP Allan Sandage (1926-2010)

Posted in The Universe and Stuff with tags , , on November 15, 2010 by telescoper

More sad news. Allan Sandage, one of the founding fathers of observational cosmology, passed away on 13th November, aged 84, of pancreatic cancer.

You can read a fuller appreciation of Allan Sandage’s contributions to astronomy and cosmology by Julianne Dalcanton over at Cosmic Variance.


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Through the Looking Glass

Posted in The Universe and Stuff with tags , , , on November 15, 2010 by telescoper

I’m afraid I’m too busy again for a proper post, so I’ll resort once again to the supply of wonderful Richard Feynman clips on Youtube. Here’s a particularly nice one, about the mysterious matter of mirrors. I might use this later on this year when I talk about parity to my particle physics class!


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Seeing Dark Matter..

Posted in The Universe and Stuff with tags , , , , on November 13, 2010 by telescoper

I found this intruiging and impressive image over at Cosmic Variance (there’s also a press release at the Hubble Space Telescope website with higher resolution images). It shows the giant cluster of galaxies Abell 1689 with, superimposed on it, a map of the matter distribution as reconstructed from the pattern of distortions of background galaxy images caused by gravitational lensing.

This picture confirms the existence of large amounts of dark matter in the cluster – the mass distribution causing lensing quite different from what you can see in the luminous matter – but it also poses a problem, in that the matter is much more concentrated in the centre of the cluster than current theoretical ideas seem to suggest it should be…

You can find the full paper here.


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Our Place in the Universe

Posted in Biographical, The Universe and Stuff with tags , , on November 10, 2010 by telescoper

Just a quick post to plug a forthcoming lecture entitled Our Place in the Universe by my former PhD supervisor, Professor John D. Barrow.

This lecture is one of a series held jointly between the University of Bath and the William Herschel Society. In fact, I gave the corresponding lecture last year on The Cosmic Web, a podcast of which is available here. It doesn’t seem like a whole year has passed since I blogged about that event!

John Barrow’s lecture will take place at 7pm on Thursday 11th November, at the Claverton Campus of the University of Bath. For further details, see the link above. I realise that it’s a bit far for local Cardiff people to get there and back in the evening, but there might be a few readers of this blog who can make it there. John is an excellent public speaker and I’d encourage anyone who can go to do so, as I’m sure it will prove very rewarding.


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Uncertainty

Posted in The Universe and Stuff with tags , on November 7, 2010 by telescoper

At the risk of turning this blog into a Feynman-fest – although I don’t think that would be such a bad thing, as a matter of fact – I couldn’t resist posting this little clip as a follow up to my previous one. In it he talks about a subject that has been a recurring motif on this blog – the importance of knowing when not to be certain.


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Stardust

Posted in Jazz, The Universe and Stuff with tags , , on November 7, 2010 by telescoper

Stellar stuff. Tune by Hoagy Carmichael.  Alto saxophone by Sonny Stitt. Images by various artists astronomers.

Sometimes I wonder why I spend
these lonely nights dreaming of a song
The melody haunts my reverie,
and I am once again with you
When our love was new
and each kiss an inspiration
But that was long ago,
now my consolation is in the stardust of a song.

Beside a garden wall,
when stars are bright,
you are in my arms
The nightingale tells his fairy tale
Of paradise where roses grew
Though I dream in vain,
in my heart it will remain
My stardust melody,
The memory of love’s refrain


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A New Theory of Dark Matter

Posted in Science Politics, The Universe and Stuff with tags , , , , , , on November 6, 2010 by telescoper

Since this week has seen the release of a number of interesting bits of news about particle physics and cosmology, I thought I’d take the chance to keep posting about science by way of a distraction from the interminable discussion of  funding and related political issues. This time I thought I’d share some of my own theoretical work, which I firmly believe offers a viable alternative to current orthodox thinking in the realm of astroparticle physics.

As you probably know, one of the most important outstanding problems in this domain is to find an explanation of dark matter, a component of the matter distribution of the Universe which is inferred to exist from its effects on the growth of cosmic structures but which is yet to be detected by direct observations. We know that this dark matter can’t exist in the form of familiar atomic material (made of protons, neutrons and electrons) so it must comrpise some other form of matter. Many candidates exist, but the currently favoured model is that it is made of weakly interacting massive particles (WIMPs) arising in particle physics theories involving supersymmetry, perhaps the fermionic counterpart of the gauge bosons of the standard model, e.g. the photino (the supersymmetric counterpart of the photon).

However, extensive recent research has revealed that this standard explanation may in fact be incorrect and circumstantial evidence is mounting that supports a  radically different scenario. I am now in a position to reveal the basics of a new theory that accounts for many recent observations in terms of an alternative hypothesis, which entails the existence of a brand new particle called the k-Mason.

Standard WIMP dark matter comprises very massive particles which move very slowly, hence the term Cold Dark Matter or CDM, for short.  This means that CDM forms structures very rapidly and efficiently, in a hierarchical or “bottom-up” fashion. This idea is at the core of the standard “concordance” cosmological model.

However, the k-Mason is known to travel such huge distances at such high velocity in random directions between its (rare) encounters that it not only inhibits the self-organisation of other matter, but actively dissipates structures once they have been formed. All this means that structure formation is strongly suppressed and can only happen in a “top-down” manner, which is extremely inefficient as it can only form small-scale structures through the collapse of larger ones. Astronomers have compiled a huge amount of evidence of this effect in recent years, lending support to the existence of the k-Mason as a dominant influence  (which is of course entirely at odds with the whole idea of concordance).

Other studies also provide pretty convincing quantitative evidence of the large mean free path of the k-Mason.

Although this new scenario does seem to account very naturally for the observational evidence of  collapse and fragmentation gathered by UK astronomers since 2007, there are still many issues to be resolved before it can be developed into a fully testable theory. One difficulty is that the k-Mason appears to be surprisingly stable, whereas most theories suggest it would have vanished long before the present epoch. On the other hand, it has also been suggested that, rather than simply decaying, the k-Mason may instead  transform into some other species with similar properties; suggestions for alternative candidates emerging from the decay of the  k-Mason  are actively being sought and it is hoped this process will be observed definitively within the next 18 months or so.

However the biggest problem facing this idea is the extreme difficulty of  detecting the k-Mason  at experimental or observational facilities. Some scientists have claimed evidence of its appearance at various laboratories run by the UK’s Science and Technology Facilities Council (STFC), as well as at the Large Hadron Collider at CERN, but these claims remain controversial: none has really stood up to detailed scrutiny and all lack independent confirmation from reliable witnesses. Likewise there is little proof of the presence of k-Mason at any ground-based astronomical observatory, which has led many astronomers to conclude that  only observations done from space will remain viable in the longer term.

So, in summary, while the k-Mason remains a hypothetical entity, it does furnish a plausible theory that accounts, in a broad-brush sense, for many disparate phenomena. I urge particle physicists, astronomers and cosmologists to join forces in the hunt for this enigmatic object.

NOTE ADDED IN PROOF: The hypothetical “k-Mason” referred to in this article is not to be confused with the better-known “strange” particle the  k-Meson.


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The Feynman Reaction

Posted in The Universe and Stuff with tags , , on November 5, 2010 by telescoper

I came across this clip of the great physicist Richard Feynman sort-of explaining magnetism, but was taken aback by some of the comments posted on Youtube in reaction to it. Some people appear to have found his response extremely arrogant, while others think he was just being honest (and trying his very best not to be patronising). I know what I think, but doubt if everyone agrees with my reaction.

I know the readership of this blog isn’t a fair sample, but I’d be very interested to see the general opinion on his comments. So please study the clip and complete the poll at the bottom.


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Finding Gravitational Lenses, the Herschel Way…

Posted in The Universe and Stuff with tags , , , , , , on November 4, 2010 by telescoper

It’s nice to have the chance to blog for once about some exciting astrophysics rather than doom and gloom about budget cuts. Tomorrow (5th November) sees the publication of a long-awaited article (by Negrello et al.)  in the journal Science (abstract here) that presents evidence of discovery of a number of new gravitational lens systems using the Herschel Space Observatory.

There is a press release accompanying this paper on the  Cardiff University website, and a longer article on the Herschel Outreach website, from which I nicked the following nice graphic (click on it for a bigger version).

This shows rather nicely how a gravitational lens works: it’s basically a concentration of matter (in this case a galaxy) along the line of sight from the observer to a background source (in this case another galaxy). Light from the background object gets bent by the foreground object, forming multiple  images which are usually both magnified and distorted. Gravitational lensing itself is not a new discovery but what is especially interesting about the new results are that they suggest a much more efficient way of finding lensed systems than we have previously had.

In the past they have usually been found by laboriously scouring optical (or sometimes radio) images of very faint galaxies. A candidate lens (perhaps a close-set group of images with similar colours), then this candidate is followed up with detailed spectroscopy to establish whether the images are actually all at the same redshift, which they should be if they are part of a lens system. Unfortunately, only about one-in-ten of candidate lens systems found this way turn out to be actual lenses, so this isn’t a very efficient way of finding them. Even multiple needles are hard to find in a haystack.

The new results have emerged from a large survey, called H-ATLAS, of galaxies detected in the far-infrared/submillimetre part of the spectrum. Even the preliminary stages of this survey covered a sufficiently large part of the sky – and sufficiently many galaxies within the region studied – to suggest  the presence of a significant population of galaxies that bear all the hallmarks of being lensed.

The new Science article discusses five surprisingly bright objects found early on during the course of the H-ATLAS survey. The galaxies found with optical telescopes in the directions of these sources would not normally be expected to be bright at the far-infrared wavelengths observed by Herschel. This suggested that the galaxies seen in visible light might be gravitational lenses magnifying much more distant background galaxies seen by Herschel. With the relatively poor resolution that comes from working at long wavelengths, Herschel can’t resolve the individual images produced by the lens, but does collect more photons from a lensed galaxy than an unlensed one, so it appears much brighter in the detectors.

 

Detailed spectroscopic follow-up using ground-based radio and sub-millimetre telescopes confirmed these ideas :  the galaxies seen by the optical telescopes are much closer, each ideally positioned to create gravitational lenses.

These results demonstrate that gravitational lensing is probably at work in all the distant and bright galaxies seen by Herschel. This in turn, suggests that in the full H-ATLAS survey might provide huge numbers of gravitational lens systems, enough to perform a number of powerful statistical tests of theories of galaxy formation and evolution. It’s a bit of a cliché to say so, but it looks like Herschel will indeed open up a new window on the distant Universe.

P.S. For the record, although I’m technically a member of the H-ATLAS consortium, I was not directly involved in this work and am not among the authors.

P.P.S. This announcement also gives me the opportunity to pass on the information that all the data arising from the H-ATLAS science demonstration phase is now available online for you to play with!


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Rapture

Posted in Art, The Universe and Stuff with tags , , on November 1, 2010 by telescoper

Glorious video of timelapse photography by, Tom Lowe, the winner of the 2010 Astronomy Photographer of the Year award.


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