Thanks to new observations made with NASA’s Chandra X-ray Observatory, astronomers have been able to confirm – after decades of indirect evidence – that the remains of disintegrating planets are falling towards white dwarfs (that is, a star already dead). , which has used up all of its fuel and shed its outer layers, leaving only a dense degraded core) over billions of years . The observed event occurred billions of years after the formation of the planetary system.
What astronomers have seen are X-ray emissions created when the rocky, gaseous material surrounding white dwarf G29-38 heated to incredible temperatures once it passed the point of no return. It is the first time that we have direct observation of this process.
And this is the fate that awaits most stars like our Sun: to become a white dwarf (it will happen to our Sun in about 5,000 million years). So far, we have discovered more than 300,000 white dwarf stars in our galaxy . We suspected that many accumulate debris from planets and other objects that once orbited them thanks to spectroscopic observations, which show that between 25 and 50% of white dwarfs have heavy elements such as iron, calcium and magnesium that pollute their atmospheres. .
But we had never seen how this material was precipitated towards the star in question.
“We’ve finally seen material actually entering the star’s atmosphere. It’s the first time we’ve been able to derive an accretion rate that doesn’t depend on detailed models of the white dwarf’s atmosphere. What’s quite remarkable is that it agrees extremely well .” with what’s been done before. Previously, measurements of accretion rates used spectroscopy and relied on white dwarf models. These are numerical models that calculate how fast an element sinks out of the atmosphere toward the star, and that tells you how much falls into the atmosphere as an accretion rate. Then you can work backwards and calculate how much of the element was in the parent body, whether it’s a planet, moon or asteroid,” writes Tim Cunningham of the Physics department at the University of Warwick in their study collected by the journal Nature.
The Chandra space observatory is normally used to observe black holes, but it can also detect less obvious emission sources, such as this chaos.
“Sounding accretion in this way provides a new technique by which we can study these systems, offering a glimpse into the likely fate of the thousands of known exoplanetary systems, including our own solar system.”
Referencia: Tim Cunningham, A white dwarf accreting planetary material from X-ray observations, Nature (2022). DOI: 10.1038/s41586-021-04300-w.
