First multiply-imaged Type Ia supernova discovered

Gravitational lensing, the bending of light which travels near massive objects, can result in distortion, magnification, and even multiple images of the original light source. The closer the light travels to the massive object the stronger the lensing effect. The magnification that results from this process allows scientists to observe objects which would normally not be visible due to their distance and brightness.

Researchers at the Oskar Klein Centre, and their international collaborators, have observed for the first time a type Ia supernova that is strongly gravitationally lensed producing multiple images. The light from the original supernova explosion (at a redshift z=0.4) is bent as it travels through a galaxy (at a redshift z=0.2) which is almost perfectly aligned between the supernova and the Earth. This alignment produced a magnification of the light from the supernova as well as four images of the source.

This composite image shows the gravitationally lensed type Ia supernova iPTF16geu, as seen with different telescopes. The background image shows a wide-field view of the night sky as seen with the Palomar Observatory located on Palomar Mountain, California. The leftmost image shows observations made with the Sloan Digital Sky Survey (SDSS). The central image was taken by the NASA/ESA Hubble Space Telescope and shows the lensing galaxy SDSS J210415.89-062024.7. The rightmost image was also taken with Hubble and depicts the four lensed images of the supernova explosion, surrounding the lensing galaxy.
This composite image shows the gravitationally lensed type Ia supernova iPTF16geu, as seen with different telescopes. The background image shows a wide-field view of the night sky as seen with the Palomar Observatory located on Palomar Mountain, California. The leftmost image shows observations made with the Sloan Digital Sky Survey (SDSS). The central image was taken by the NASA/ESA Hubble Space Telescope and shows the lensing galaxy SDSS J210415.89-062024.7. The rightmost image was also taken with Hubble and depicts the four lensed images of the supernova explosion, surrounding the lensing galaxy. Credit: ESA/Hubble, NASA, Sloan Digital Sky Survey, Palomar Observatory/California Institute of Technology

Type Ia supernovae are thought to always have the same brightness when they explode and thus have been used to measure distances in the Universe. Distance measurements to a large number of Type Ia supernovae led to the discovery that the expansion of the Universe is accelerating. The team will now use the difference in the time it takes the light from each of the four images of the single supernova to measure the current expansion rate of the Universe, the Hubble Constant.

These results are published in the journal Science in an article titled, iPTF16geu: A multiply-imaged gravitationally lensed Type Ia supernova.

For more information please contact:
Ariel Goobar ( ariel@fysik.su.se)
Rahman Amanullah (rahman@fysik.su.se)

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