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Gravitational lensing in astronomy and supernovae

Jumping right to the point, astronomers recently discovered a gravitationally lensed supernova.

Simply put, a supernova is a star blowing up. They are some of the brightest objects in the sky. In fact, the most recent supernova in the milky way galaxy was in 1604 and the supernova was so bright that people could see it in the day for over three weeks. It is worth noting that this supernova is at a distance of 20,000 light years.

Gravitational lensing on the other hand is the bending of light due to a massive object near it's path. Einstein's theory of general relativity was in fact experimentally proved when gravitational lensing was first observed as light from stars behind the sun bent around it to reach us. Galaxy and galaxy clusters are the major sources of gravitational lensing from an astronomical perspective. Coincidentally, if another galaxy or part of a galaxy (object galaxy) is behind this massive galaxy cluster closer to us (field galaxy), the object galaxy's features are lensed because of the field galaxy cluster. Such a lensing would create multiple images of the object galaxy as light travelled around the field galaxy along multiple paths.

Incredible lensing features can be observed such as the Einstein's cross. It is interesting to note that because of a difference in path traveled by the light along the different focal paths, if there are temporal variations in the object galaxy, such variations are observed to have a delay between the multiple images of the object galaxy created. Studying such variations can help constrain cosmological parameters such as H_o, the hubble parameter.

Coming back to the point, astronomers recently discovered a quadruply gravitationally lensed supernova. And interesting science can be expected to pour out of the data from these observations. One of the first papers I've noticed as a follow-up of the detection is a new paper constraining the lens model of the field galaxy. It'll be interesting to see what more comes out of such observations.

And last but not the least, these observations were carried out from space by the Hubble Space Telescope (HST). Earth-based observatories have a small chance of observing such faint supernova, especially when they happen at such large distances and this is a testament to the golden goose that is the HST, an investment that keeps on giving back to the scientific community.

[1] Kelly P Et al.
[2] Keren Sharon, Traci L. Johnson
[3] Masamune Oguri

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