The X-ray burst was visible for four hours.
REPUBLIKA.CO.ID, JAKARTA — German astronomers discovered a phenomenon that had never been seen before in space. With the help of the eROSITA X-ray telescope, now more than 1.5 million kilometers from Earth, they first saw white dwarf star which explodes X-rays.
White dwarfs are the remains of a dying star that has run out of its fuel supply. They may spin at very high speeds, up to 100 revolutions per second. Such white dwarfs are known as millisecond white dwarfs.
White dwarfs emit a lot of radiation. However, it was only recently discovered that they can also emit X-rays.
The phenomenon was first noticed on July 7, 2020, when the telescope was pointed at an area of the sky where the unexplained event was expected to occur. According to astronomers, the event happened suddenly.
The X-ray burst was visible for four hours. During that time the telescope was not very prepared for this sudden excess of X-rays.
These X-ray flashes only last a few hours and are nearly impossible to predict. However, the observation instrument must be pointed directly at the explosion at the right time.
“So-called novae occur all the time, but detecting them in the first moments when most of the X-ray emission is generated is very difficult. Not only is the short duration of the flash a challenge, but also the fact that the spectrum of the X-rays emitted is very soft.” said Dr. Victor Doroshenko from Tubingen University, reported by Nature.
Soft X-rays are not very energetic and are easily absorbed by the interstellar medium. So astronomers cannot see very far in this band, which limits the number of observable objects, be they novae or ordinary stars.
“Telescopes are usually designed to effectively capture harder X-rays where absorption is less important, and that’s the reason why they miss events like this,” concludes Doroshenko.
Despite the fact that the event caught astronomers and telescopes off guard and only lasted a few minutes, the data collected has helped scientists better understand how white dwarfs erupt.
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