Everything comes to an end, even stars! When these burning balls of hydrogen and helium use up all their fuel they shrink to white dwarfs. In some rare cases, these dead stars can flare back to life in an extremely hot explosion, producing a fireball of X-ray radiation.
For the first time, researchers based across several German institutions have captured this moment and recently published their findings in Nature. X-ray explosions such as these were theoretically predicted more than 30 years ago, however, this is the first-time physical evidence has been gained to support the idea.
Lead-author Ole König, from Friedrich-Alexander-Universität Erlangen-Nürnberg, explains the serendipitous moment: “It was to some extent a fortunate coincidence, really. These X-ray flashes last only a few hours and are almost impossible to predict, but the observational instrument must be pointed directly at the explosion at exactly the right time.”
Introducing the eROSITA X-ray telescope
The finding was thanks to the X-ray telescope, eROSITA. Orbiting about a mile from Earth, this incredible machine has been surveying the skies for low-energy X-ray radiation since 2019.
Although, these intense inputs of X-rays were a little too much for eROSITA to handle. “The problem in this particular case was … that after 30 years with no photons we suddenly had too many, which distorted the spectral response of eROSITA, which was designed to detect millions of very faint objects rather than one but very bright,” adds Victor Doroshenko, an astrophysicist who worked on the project.
What did they discover?
The researchers then took to analyzing the overexposed image to gain more information about the complex white dwarf explosion. Through teamwork between the facilities, they were able to crack the case, illustrating the importance of collaboration in modern science.
They found that the explosion generated a fireball with a temperature of around 327,000 Kelvin, around 60 times hotter than the sun. The expulsion of X-rays occurred on the surface of the star, which started around the same size as our sun, however, the stellar corpse then shrunk to the size of our Earth in a dense package.
Studying natural phenomena such as this is extremely important in grasping the wider world around us. Astronomy is vital in understanding where we came from, where we are going, and the practical applications of the laws of physics in general. From this, imaginative innovations that help our planet can be created.
Source study: Nature – X-ray detection of a nova in the fireball phase