Space

Astronomers see supernova explosion using galaxies as lenses

Astronomers see supernova expl...
MACS J1149.6+2223 and the images of the supernova
MACS J1149.6+2223 and the images of the supernova
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MACS J1149.6+2223 and the images of the supernova
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MACS J1149.6+2223 and the images of the supernova
Brad Tucker, from ANU Research School of Astronomy and Astrophysics, was part of the team studying the gravitational lens
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Brad Tucker, from ANU Research School of Astronomy and Astrophysics, was part of the team studying the gravitational lens
Spectrographic instruments at the Keck observatory were used to study the gravitational lens
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Spectrographic instruments at the Keck observatory were used to study the gravitational lens
Composite image of MACS J1149.6+2223 and the supernova images
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Composite image of MACS J1149.6+2223 and the supernova images
How a gravity lens produces multiple images
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How a gravity lens produces multiple images
sequence images showing the supernova behind MACS J1149.6+2223
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sequence images showing the supernova behind MACS J1149.6+2223
Images showing the supernova before and after its appearance and a biscuit as an illustration
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Images showing the supernova before and after its appearance and a biscuit as an illustration
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A team of astronomers led by the Australian National University (ANU) has discovered a lens of galactic proportions. Using the Hubble Space Telescope and the Keck Observatory in Hawaii, the scientists saw a supernova not once, but four times by using the gravity of a distant cluster of galaxies to act as a natural lens that magnified and quadrupled the image of the exploding star.

Predicted by Einstein's general theory of relativity, in 1937 it was suggested that a cluster of galaxies would have sufficient mass to bend light and act as a lens tens of millions of light years across by distorting the space-time continuum. In this case, it's a supermassive cluster called MACS J1149.6+2223, which is located more than 5 billion light-years from Earth.

Behind this cluster is Supernova Refsdal, which is in an elliptical galaxy 9.3 billion light-years from Earth and is normally too distant to be observed from our planet. It's a Type 1A supernova that, put simply, is formed by a binary pair of stars where one becomes a white dwarf star and sucks the gas from the companion star until it explodes.

Unlike a glass lens, there's no focal point in a gravitational lens, so the object on the far side of the cluster would appear as a ring or a set of multiple magnified images. In the case of Supernova Refsdal, four images were created in what's known as an Einstein's Cross and the image appears and reappears periodically over decades in a predictable pattern.

How a gravity lens produces multiple images
How a gravity lens produces multiple images

According to the team, this is the first such phenomenon to be seen in over two decades of searching. It was found by accident by Dr Patrick Kelly from the University of California, Berkeley using archival images from the Hubble telescope and later confirmed by instruments at the Keck observatory in Hawaii.

But the significance of this phenomenon is more than seeing four supernovae for the price of one. The team says that by studying this gravitational lens, it will not only test the theory of relativity, but also allow scientists to measure the cosmic expansion rate, better deduce the distribution of matter in the universe, gain a better understanding of the nature of gravity, and estimate the amount of dark matter and dark energy in the universe.

"It’s perfectly set up, you couldn’t have designed a better experiment," said Brad Tucker, from ANU Research School of Astronomy and Astrophysics. "You can test some of the biggest questions about Einstein’s theory of relativity all at once – it kills three birds with one stone."

The team’s results are published in Science.

The video below discusses viewing a supernova through a gravitational lens.

Source: Australian National University

'Cosmic magnifying glass' used to find ancient supernova

View gallery - 7 images
4 comments
Reid Barnes
When a light ray bends, if due to gravity, as Einstein said, and because the geometry is not Euclidean as Einstein said--to say it figuratively, if space is curved and there are no straight lines in the gravitational field--this may seem to explain the phenomenon, but is it good, if it seems to explain but doesn’t explain? If the light bends and the geometry is Euclidean, this means something further about the cause remains to be discovered. Is it good to think we have an explanation, when we should still be looking for the explanation? A Facebook Note explains why the non-Euclidean geometry of the general theory of relativity became self-contradicting. You can understand it even if your math education did not exceed elementary geometry: https://www.facebook.com/notes/reid-barnes/where-20th-century-physicists-and-cosmologists-went-wrong/399956633390250
Kevin Ritchey
And to think we are soon going to let such a fine piece of equipment just flounder because it's too much effort to maintain. Because of the loss of the shuttle and with no suitable replacement, all expensive satellites and even ISS are at the mercy of space and time. Hubble has provided so much. Perhaps it's time to reevaluate our priorities once again. We require a more suitable, less expensive yet more versatile space truck. Or, at the very least, ask our alien space buddies for help. Heaven knows, they give us enough fodder for lousy TV shows as it is. Time for some payback. Ha!
EH
Modelling gravitational lensing as being due to a slightly higher refractive index near large masses rather than curved space is much easier and more than good enough for nearly all situations (aside from really exotic ones involving e.g. rapidly rotating neutron stars). Gauge Theory Gravity ( http://en.wikipedia.org/wiki/Gauge_theory_gravity ) basically takes this flat-space approach, though with an additional rotational gauge field that can handle rotational effects.
The action of a spherical mass on light can be visualized as a spherical gradient-index lens, like a crystal ball with a refractive index that smoothly fades out farther from the mass.
Ranscapture
A photon exists, therefore it is affected by gravity and its trajectory is bent just like an arrow on earth. That doesn't mean space is bending. Also just because more distant light is finally reaching us doesn't mean the universe is expanding, it just means that more is being revealed.