SN Refsdal

SN Refsdal
SN Refsdal (inset picture) and galaxy cluster MACS J1149.6+2223. Credit: Hubble/NASA/ESA/STScI/UCLA
Observation data (Epoch J2000)
Supernova type	Unknown
Constellation	Leo
Right ascension	11h 49m 35.45s
Declination	22° 23′ 44.84″
Discovery date	11 November 2014 Patrick Kelly (GLASS)
Distance	z=1.49
Physical characteristics
Progenitor	unknown
Notable features	First multiply-lensed supernova

SN Refsdal is the first detected multiply-lensed supernova, visible within the field of the galaxy cluster MACS J1149+2223. It was given its nickname in honor of the Norwegian astrophysicist Sjur Refsdal, who, in 1964, first proposed using time-delayed images from a lensed supernova to study the expansion of the universe. The observations were made using the Hubble Space Telescope.

Einstein cross

The host galaxy of SN Refsdal is at a redshift of 1.49, corresponding to a comoving distance of 14.4 billion light-years and a lookback time of 9.34 billion years. The multiple images are arranged around the elliptical galaxy at z = 0.54 in a cross-shaped pattern, also known as an "Einstein cross".

When the four images fade away, astronomers predict they will have the rare opportunity to see the supernova again. This is because the current four-image pattern is only one component of the lensing display. The supernova may have appeared as a single image some 40-50 years ago elsewhere in the cluster field, and it is expected to reappear once more in about one year. The magnifications and staggered arrivals of the supernova images will help astronomers probe the cosmic expansion rate, as well as the distribution of matter and dark matter in the galaxy and cluster lenses.

Reappearance

The image to the left shows a part of the deep field observation of the galaxy cluster MACS J1149.5+2223 from the Frontier Fields programme. The circle indicates the predicted position of the newest appearance of the supernova. To the lower right the Einstein cross event from late 2014 is visible. The image on the top right shows observations by Hubble from October 2015, taken at the beginning of the observation programme to detect the newest appearance of the supernova. The image on the lower right shows the discovery of the Refsdal Supernova on 11 December 2015, as predicted by several different models.

The supernova Refsdal reappeared punctually at the predicted position between mid November 2015 and December 11 2015 (with the exact date being uncertain by approximately one month which is the interval between two consecutive Hubble observations), in excellent agreement with the blind model predictions made before the reappearance was observed.

See also

• the Einstein Cross, the gravitationally lensed quasar that gave rise to the term "Einstein cross"
• Gravitational lens, the phenomena that creates visual patterns such as an Einstein cross

External links

• Images of first SN Refsdal in March and reappeared in December 2015 at hubblesite.org
• NASA’s Hubble Discovers Four Images of Same Supernova Split by Cosmic Lens - by NASA
• Predicted Reappearance of SN Refsdal (March 2015)
• The image taken by Hubble around November 2015 shows new supernovae 'SX' in multiply image system at astro.berkeley.edu.
• Hubble Hangout December 17 2015 discussing SN Refsdal
• View of Exploding Star Appears, Right on Cue National Geographic Society 17 December 2015