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posted by martyb on Saturday November 22 2014, @07:35AM   Printer-friendly
from the that's-a-bright-idea! dept.

For several decades, astronomers have found and studied gravitational lenses: systems in which light from a distant source is bent as it passes a massive object, so that we see several images (magnified and distorted) of that source. The light from each image takes a different path to reach us, which can cause one image to vary before or after another; the lag in time between images, together with the redshifts of the source and the lensing object, can yield accurate distances.

Today's Astronomer's Telegram, number 6729, announces a very special gravitational lens: one which produces multiple images of a supernova! Supernovae are luminous enough to be seen at great distances (the host of this one is at z=1.49, very far away), and they rise and fall strongly in brightness over just a few weeks or months. This combination should allow astronomers to measure very accurate time lags between the three bright images of the supernova and use that information as a strong check on our understanding the size, age, and expansion rate of the universe.

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The First Predicted Supernova Appearance by Gravitational Lensing 11 comments

Well, not precisely calling a supernova, but good enough to be exciting. A massive cluster is between us and the supernova, resulting in gravitational lensing. An article in astronomy.com says:

Many stars end their lives with a with a bang, but only a few of these stellar explosions have been caught in the act. When they are, spotting them successfully has been down to pure luck — until now. On 11 December, 2015, astronomers not only imaged a supernova in action, but saw it when and where they had predicted it would be. As the matter in the cluster [bending the light] — both dark and visible — is distributed unevenly, the light creating each of these images takes a different path with a different length [and taking a different time to reach Earth].

The supernova was seen in one of the images a year ago. It implies that the watchers were able to calculate the paths the light took, and predict when the supernova would appear in another image — and got it right. So, the takeaway is that no, they weren't able to make the prediction based on the instablility of the star, but they were able to calculate gravitational effects and predict the supernova would show elsewhere this month. Isn't that enough?


[Editor's Note: I realize that this covers much of the same material as this story from November, but in reading over the links provided here, they were more understandable to those of us with little understanding of the subject matter. - CMN]

[Editor's Note: Changed title from "The First Predicted Supernova" to "The First Predicted Supernova Appearance by Gravitational Lensing" - CMN]

Original Submission

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  • (Score: 0) by Anonymous Coward on Saturday November 22 2014, @01:06PM

    by Anonymous Coward on Saturday November 22 2014, @01:06PM (#118754)

    The article contains no pics, links to only one which is unprocessed, with a lot of noise, and no clear indications of what to watch.-Ignacio Agulló

    • (Score: 1) by kanweg on Saturday November 22 2014, @01:39PM

      by kanweg (4737) on Saturday November 22 2014, @01:39PM (#118760)

      At the bottom there are two links, the top one being the one showing the supernova (s1, s2, s3).

      Bert

    • (Score: 3, Informative) by hubie on Saturday November 22 2014, @02:27PM

      by hubie (1068) Subscriber Badge on Saturday November 22 2014, @02:27PM (#118770) Journal

      The pic is right there [stsci.edu]. The text talks to the lensed images S1 through S4, and the image clearly points out S1 through S3. Astronomers typically don't wait for an artist to come up with an "artist's rendition" before announcing results to their colleagues.

  • (Score: 2) by dx3bydt3 on Saturday November 22 2014, @03:05PM

    by dx3bydt3 (82) on Saturday November 22 2014, @03:05PM (#118775)

    Another factor that might allow us to glean some information is the brightness observed of the lensed supernova. Gravitationally lensed objects are typically distant quasars or galaxies, both of which vary greatly in luminosity i.e. some galaxies are bigger and brighter, quasars too can have different luminosities. Supernovae on the other hand are special. By observing the light curve the type of supernova can be determined, and knowing this, the luminosity of the supernova itself can be known. Barring losses from intervening dust and gas the known luminosity of the object being gravitationally lensed could tell us something about the other distant objects we've observed this way.

    • (Score: 2) by hellcat on Saturday November 22 2014, @05:49PM

      by hellcat (2832) Subscriber Badge on Saturday November 22 2014, @05:49PM (#118834) Homepage

      So what are the magnitudes at the end of the article for?

      Astronomers don't use candles.

      • (Score: 2) by dx3bydt3 on Saturday November 22 2014, @07:04PM

        by dx3bydt3 (82) on Saturday November 22 2014, @07:04PM (#118867)

        Astronomers most certainly do use candles, but I wasn't referring to wax candles. The standard candles [wikipedia.org] my subject refers to are stars or supernovae of known luminosity used to determine distance.
        These include cepheid variables [wikipedia.org] and supernovae. If you know the absolute magnitude of an object, the observed brightness can be used to compute how far away the object is.