Astronomers from Spain, using powerful space telescopes NASA’s Chandra and ESA’s XMM-Newton, have discovered four previously unknown remnants of giant stellar explosions in the galaxy NGC 7793. This discovery will help unlock the secrets of the life and death of stars far beyond our galaxy. The results are published on the arXiv preprint server.
Space ghosts
Supernova remnants (SNRs) are hot clouds of gas and dust scattered by the explosion of a star that became a supernova. These impressive structures, resembling cosmic nebulae, exist for hundreds of thousands of years before completely dissolving into interstellar space. Studying them is key to understanding how star explosions influence the formation of galaxies and the chemical composition of the universe.
The galaxy NGC 7793, located 12 million light-years away from us, has attracted the attention of scientists. This spiral galaxy is known for its large number of supernova remnants visible in the optical spectrum. This made it an ideal field for searching for their X-ray echoes using the ultra-sensitive instruments Chandra and XMM-Newton.
X-ray hunters
Maria Kopsacheili’s team at the Institute of Space Sciences (ICE-CSIC) carefully analyzed 19 years of Chandra archive data, taking advantage of its high resolution. Scientists searched for X-ray sources that exactly matched known optical SNRs. Data from XMM-Newton helped to study the radiation spectrum of potential candidates.
The search was successful. Among the dozens of X-ray sources discovered, five clearly matched the optical SNRs. One of them (X15) was previously known, but the other four (X11, X13, X25, X38) are completely new discoveries. All of them emit “soft” X-rays characteristic of hot plasma with temperatures exceeding 2.5 million degrees Celsius and contain bright spectral lines of oxygen and neon.
Mysterious candidates
The study found two more ghosts – sources X23 and X42. Although they are not detected in the optical range, their stable, “soft” X-ray radiation is very similar to the remnants of supernovae. Scientists have classified them as promising candidates for further observation.
The discovery of new SNRs in galaxies outside our Local Group is a rare achievement. It not only extends the list of known cosmic catastrophes in the past, but also provides invaluable data on the properties of the interstellar medium in NGC 7793 and the physical processes accompanying stellar explosions. Each such ghost tells a unique story about the galaxy’s past.
Earlier, we reported on how Hubble photographed a galaxy with a supernova.
According to phys.org
