On July 7, 2020, the X-ray instrument eROSITA captured an event that had been theorized and never seen before. A nova detonation on a white dwarf star produced a fireball explosion of X-rays.
It was a fortunate coincidence, according to Ole K, who led the team.
A white dwarf is a dense star that forms when a low-mass star uses up all its fuel. White dwarfs are the size of a planet. Sometimes the dead stars will explode in a super-hot explosion and produce a fireball of X-ray radiation, and then gradually return to their original brightness. A nova is not an explosion of a star where most of the material is ejected from the star, but is instead an event in the life of a white dwarf.
novae happen all the time, but detecting them during the very first moments when most of the X-ray emission is produced is hard, said Dr. Victor Doroshenko from TFC. Telescopes are usually designed to be most effective in harder X-rays where absorption is less important.
The main instrument on the Russian-German Spectrum- Roentgen-Gamma mission is called eROSITA. The first all-sky survey in the medium energy X-ray range is being conducted in space.
The phase immediately after the fusion nova event has been studied for 30 years. The nova should be visible as a soft X-ray flash before it becomes visible in the optical range. The best way to see it is to point your telescope at the right time.
The team said in their paper that there was no X-ray source on either side of the flash when it was visible.
The nova happened on YZ Reticuli, also known as Nova Reticuli 2020, which was a naked eye nova in the constellation Reticulum. It was previously known as a VY Sculptoris type object. Nova Reticuli 2020 was spotted by a comet hunter. It was barely visible to the naked eye in the southern hemisphere.
The physical origin of X-ray emission coming from white dwarf atmospheres is well understood, and we can model their spectrum from first principles.
The problem in this particular case was that after 30 years without a single photon, we suddenly had too many, which distorted the eROSITA response.
novae run out of fuel very quickly and the X-ray radiation be weakened until it becomes visible light. Since novae are only visible after the X-ray flash, it's hard to predict if there will be an outbreak. After the eROSITA detection, the visible light reached Earth 12 hours later.
The star was so bright that it could be seen on the night sky by the bare eye.
Sources:
Paper in nature.
The press release is from the University.
All Rights Reserved © 2024
