Hubble Weighs In: CSL-1 Not a Cosmic String

By Mark Trodden | January 12, 2006 12:55 pm

There has been some excitement in the cosmology and string theory communities recently regarding the observation of a pair of images (optimistically named CSL-1), with characteristics and separation such that they are candidates to arise from a single object lensed by a cosmic string. If this interpretation held up it would have deep and far ranging implications for our understanding of fundamental physical laws, implying either a field theory phase transition at high energies or that it is possible for some superstrings from the early universe to remain macroscopic.

The only way to get a real check of the status of CSL-1 was to get a good look at it with the Hubble Space Telescope (HST), and my postdoc Levon Pogosian just forwarded an email to me, informing him that the HST observations of CSL-1 are now in and that it is not a cosmic string, but rather merely a pair of interacting elliptical galaxies sitting in a rather faint cluster.

Here’s what I think is the HST image

Oh well, I imagine the search will continue.

  • Sean

    Excellent; science marches on. Am I supposed to be able to tell that it’s not a lensing string just from the image? I guess the galaxies don’t look exactly the same shape. Or is spectral information involved?

  • Mark

    I don’t know, although there might be something simple as you say.

  • Julianne

    It’s entirely morphological. The galaxies have different shapes and orientations Moreover, the orientation of the lower galaxy and the slight extension in the faint light to the upper left of the upper galaxy are suggestive of an interaction.

  • Chaz


    The shape gives it away – they don’t form a mirror image (probably more obvious to a computer than to people). Though apparently, the spectra are identical!!


  • Dissident

    To me that looks like a picture of a cell splitting… but assuming it is what you guys say it is, couldn’t the difference in shape be accounted for by the cosmic string being at an angle to our line of sight? Just an idle thought, please kill it before I develop a compulsion to do the math.

  • Lubos Motl

    If there were a string, you would simply have to see a discontinuity of the picture along the string. And yes, the shapes would have to be more similar.

  • thomas

    thanks for this one! I just told some students this morning about this case, but now I can tell them otherwise tomorrow :-)

  • Plato

    As a Stringevangelist my world is coming apart? :)

    Andrey Kravstov provides for interesting views of early universe formation. Am I to take it then, that this area might be in trouble?

    Just some additonal prep information given here.

    Maybe you could expand a bit on what your saying Lubos?

  • Peter Woit’s Bastard Child

    Did anyone really think in his or her heart that this was a cosmic string? Honestly? Come on.

  • Lubos Motl

    If you want to see the picture from the Korean Space Telescope Hwang Woo-Suk that proves that there is a cosmic string :-), see the bottom of

  • Dissident

    #10: Ahem, not to spoil your fun or anything Lubos, but what I see at the bottom of that page is a Google ad for “The Final Theory”, claiming to be “The bestselling book our scientists hope you never read” and an invitation to “Find out why!”…

  • Lubos Motl

    Joe was saying that the probability it was a cosmic string – or similar accessible incident would reveal a cosmic string – was around 10%. I still agree that there was a significant enough chance.

    Dear Dissident, when I said “bottom”, I did not mean a complete bottom.

  • Pingback: Not Even Wrong » Blog Archive » The First Evidence For String Theory? Not.()

  • Slacrates

    Imagine the comments at ‘Not Even Wrong’ if it turned out to be a probable cosmic string. Richard Hoagland would add it to his repetoire of conspiracies.

  • Count Iblis

    Hi Lubos,

    I thought that you didn’t like Bayesian reasoning. :)

  • amanda

    “Did anyone really think in his or her heart that this was a cosmic string? Honestly? Come on.”

    I put this question to a few people. The answers were depressingly similar. They were all variants on, “No, I didn’t, because I no longer expect anything to work these days.” An extension of the attitude most people have to everything on hep-th these days……

  • Lubos Motl

    Dear Count Iblis,

    I still don’t like it. Moreover, we have a new argument against it. The correct figure for the probability that CSL-1 was a cosmic string lensing was 0%. 😉


  • Pingback: Thoughts on science and life » Blog Archive » CSL-1: The End of Cosmic Strings?()


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About Mark Trodden

Mark Trodden holds the Fay R. and Eugene L. Langberg Endowed Chair in Physics and is co-director of the Center for Particle Cosmology at the University of Pennsylvania. He is a theoretical physicist working on particle physics and gravity— in particular on the roles they play in the evolution and structure of the universe. When asked for a short phrase to describe his research area, he says he is a particle cosmologist.


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