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Supernova Casts Doubt on "Standard Candle" 132

Posted by kdawson
from the chandrasekhar's-the-limit dept.
Krishna Dagli writes, "A supernova more than twice as bright as others of its type has been observed, suggesting it arose from a star that managed to grow more massive than theoretically thought possible. The observation suggests that Type 1a supernovae may not be 'standard candles' — all having the same intrinsic luminosity — as previously thought. This could affect their use as probes of dark energy, the mysterious force causing the expansion of the universe to accelerate."
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Supernova Casts Doubt on "Standard Candle"

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  • by Silver Sloth (770927) on Thursday September 21, 2006 @08:01AM (#16152738)
    because
    CFHT is a joint facility of:

    * National Research Council of Canada (see also Herzberg Institute of Astrophysics),
    * Centre National de la Recherche Scientifique of France (see also CNRS/INSU ), and
    * University of Hawaii (see also UH/IfA ).
    i.e. two national bodies and one local body. This is all on their website http://www.cfht.hawaii.edu/ [hawaii.edu]
  • by StupendousMan (69768) on Thursday September 21, 2006 @08:13AM (#16152793) Homepage
    I study supernovae for a living.

    The Nature paper in which this work is published has a figure showing all the measurements of this supernova's brightness; you can see it on Nature's web site at

    http://www.nature.com/nature/journal/v443/n7109/fi g_tab/nature05103_F1.html [nature.com]

    There are four measurements near time of maximum light, in the red (r) and near-infrared (i) passbands. There are many more measurements starting about 15 days after maximum light in the rest frame, including some in a blue-green (g) passband. Here's what the researchers did to find the maximum brightness of this supernova, so that they could compare it to others:

        a) fit models based on the light curves of other supernovae to the r and i measurements,
                      and the late-time g measurements

        b) choose a different passband -- the greenish V passband of the Johnson-Cousins system,
                      which is closest to their own g passband (the one with no data at max light)

        c) use their models to estimate what the light curve in the V filter would have been

    This can be a tricky business. Their major conclusion, that this supernova was more luminous than typical ones, is probably correct, but their claim that they can measure the peak magnitude in the V-band to an uncertainty of 6 percent seems a bit bold.

    As the press release states, if atypical SNe are very rare, then this probably doesn't have any major impact on the use of Type Ia SNe in cosmology.

  • by rucs_hack (784150) on Thursday September 21, 2006 @08:15AM (#16152800)
    It's a pretty familier story, and essential for the advancement of science.

    The standard candle was a theory, one that worked well, and now it's in doubt, indicating either that its wrong, or it's incomplete. I'd vote for the latter personally.
    That's usually a safe bet...

    That's how things move forward.
    I shortcut this process. I proved one of my hypothesis wrong even though it had withstood initial tests which indicated correctness. It probably saved a lot of time, but lost me a conference trip, dammit.
  • Re:Gravity Lensing? (Score:4, Informative)

    by ByteSlicer (735276) on Thursday September 21, 2006 @08:45AM (#16152985)
    Probably not. Gravitational lensing would cause a noticible shift [wikipedia.org] in the star's spectrum.
  • Re:Gravity Lensing? (Score:1, Informative)

    by Anonymous Coward on Thursday September 21, 2006 @11:23AM (#16154313)
    "...could it be a foreground star and not associated with that galaxy at all?"

    Simply put, no.

    A light spectrum clearly identifies a supernova for what it is. There is nothing else like it. Also, the redshift in the supernova and surrounding stars gives the distance fairly accurately.

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