Scientists detected the largest supernova remnant ever

Scientists find the largest supernova remnant by looking in right place.

Using powerful new X-ray telescope eROSITA, an international team of scientists has detected the largest supernova remnant ever discovered with X-rays, dubbed Hoinga.

The aim was to consolidate expertise across numerous frequencies, from radio to X-ray, to look for many supernova remnants. Scientists were expecting to discover multiple supernovas over the coming years, but they got surprised after detecting one almost immediately.

The Hoinga supernova remnant is very large and located far from the galactic plane. With a diameter of about 4.4 degrees, it covers an area about 90 times bigger than the size of the full Moon. Moreover, it lies very far off the galactic plane, which is very unusual.

Astrophysicist Dr. Natasha Hurley-Walker, from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR), worked with Astronomy Australia Limited (AAL) to form a collaboration with the international team, including scientists from the Max Planck Institute for Extraterrestrial Physics and the National Institute for Astrophysics.

Dr. Hurley-Walker said“The eROSITA telescope, which is onboard the Russian-German SRG satellite, is 25 times more sensitive than its predecessor ROSAT, so we expected to discover new supernova remnants in coming years, but were pleasantly surprised to have one appear straight away. Adding to our excitement, Hoinga is the largest supernova remnant ever discovered via X-rays, in terms of apparent size: about 90 times larger than the full moon.”

Composite image of Hoinga taken at 1.4 GHz and 2.3 GHz by the CHIPASS and SPASS radio survey
Composite image of Hoinga taken at 1.4 GHz and 2.3 GHz by the CHIPASS and SPASS radio surveys. The blue colour is arbitrary; fore- and background sources were removed from the images to increase the visibility of the diffuse radio emission from the supernova remnant. Credit: CHIPASS/SPASS/N. Hurley-Walker, ICRAR-Curtin (Radio)

“An enduring mystery surrounding supernova remnants was the shortfall between the expected number of them in our galaxy and the number identified through past surveys.”

“We expect there to be about 1200 supernova remnants in our galaxy; however, only about 300 have been found so far.”

“By sifting through archival radio data, we discovered Hoinga had been sitting there waiting to be discovered in surveys up to ten years old, but because it was high above the plane of the Milky Way, it was missed.”

“Supernova remnants are not typically expected to be found at high Galactic latitudes, so these areas are not usually the focus of surveys, meaning there may be even more of these overlooked remnants out there waiting to be discovered.”

“The radio observations made it possible for us to work out that it is a middle-aged remnant relatively close to Earth, calculations that would have been far less accurate with the X-ray data alone.”

Journal Reference:
  1. W. Becker et al. Hoinga: A supernova remnant discovered in the SRG/eROSITA All-Sky Survey eRASS1. DOI: 10.1051/0004-6361/202040156

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