Astronomers at the University of Warwick have discovered the remnants of dead Earth-like planets in the atmosphere of four white dwarfs nearby to the solar system. This is reported in an article published in the journal Nature Astronomy.
The researchers analyzed spectroscopic data from the Gaia telescope, covering more than a thousand white dwarfs. They detected an unusual signal from one of the stars, corresponding to the absorption line of lithium. Similar signals were soon discovered in three other white dwarfs, one of which also included a potassium absorption line. Comparing the ratios of the identified elements, the scientists found that they correspond to the chemical composition of the crust of rocky planets similar to Earth and Mars, which evaporated and mixed inside the outer layers of the stellar atmosphere over two million years.
Lithium and potassium are indicators of crustal material, as they are not present in high concentrations in the mantle or core, the scientists said.
The outer layers of white dwarfs contain up to 300 thousand gigatons of rock debris, including up to 60 gigatons of lithium and three thousand gigatons of potassium, which is equivalent to a 60-kilometer sphere with the density of the earth's crust. The total amount of material is not enough for the planet, so scientists believe that they have discovered only isolated fragments of celestial bodies that died about 10 billion years ago. Around the stars, most likely, a disk of matter rotates, which from time to time falls on white dwarfs and quickly burns up.
