Astronomers are looking for the bones of dead planets in the bodies of dead stars – and they may have found only a few.
In an article published in the magazine on February 11 Natural Astronomy, a team of researchers described how they used data from the Gaia space satellite to look into the atmosphere of four white dwarfs – the shrunken, crystalline shells of once massive stars that burned through all their fuel. The team wrapped themselves in the hot soup of hydrogen and helium around the stars and found clear traces of lithium, sodium and potassium metals abundant in planetary crusts – in the exact ratio they would expect in a rocky planet.
“By comparing all of these elements with different types of planetary material in the solar system, we found that the composition clearly differs from anything but one type of material: continental crust,” said lead author Mark Hollands, an astrophysicist at the University of Warwick. in England, Live Science said by email.
According to Hollands and his colleagues, the presence of these crusty metals suggests that each of the old, faded stars they analyzed could ever sit in the middle of a solar system that is not so different from ours; then, in their dying ages, those stars tore their solar systems to shreds and accumulated the excess.
Our solar system can also share this fate.
When stars die
Over billions of years, stars with masses between about one-tenth and eight times the mass of the sun burn through their nuclear fuel. When that happens, those old stars shed their fiery layers and shrink into a warm, white, compact core that packs half the sun’s mass into a ball no wider than the earth – a white dwarf.
These smoldering bulbs of energy have an extremely strong gravity and are incredibly hot and clear. But the older a white dwarf gets, the cooler and dimmer it becomes, and the more wavelengths of light become visible in its atmosphere. By studying the wavelengths, scientists can calculate the elemental composition of the star’s atmosphere.
Most white dwarf atmospheres are dominated by hydrogen or helium, the researchers said, but they could be “polluted” by other elements if the dead star’s severe gravity pulls material out of space around it. For example, if a white dwarf sucks in the pieces of a broken planet, then “any elements in the destroyed object can release their own light and give a spectral fingerprint that astronomers could possibly spot,” Hollands said.
In their new article, Hollands and his colleagues targeted four old white dwarfs within 130 light-years of Earth to see if their atmosphere contained evidence of planetary remains. Each dead star was between 5 billion and 10 billion years old and cool enough for astronomers to detect wavelengths of light emitted by metal elements from their dim atmosphere.
In all four of the old stars, the researchers detected a combination of lithium and other metals that matched the composition of planetary debris. ‘One star, whose team got a particularly clear look, contains metals in its atmosphere that provide an almost perfect match for the earth’s continental crust,’ Hollands said.
For the researchers, there is only one logical explanation: the ancient white dwarfs still hold the smoldering remains of the very planets on which they once gave their light. To end up in an atmosphere of a white dwarf, the planetary remains had to be drawn in millions of years ago by the intense gravity of the star, after the star finished as a red giant and put its outer layer of gas into space. , said Hollands.
Any planets near the star would be wiped out during the red giant phase (just as Mercury, Venus and possibly the Earth would be engulfed by our sun in our days of death), but any planets that survived long enough to see their sun ‘ a white dwarf would also see the gravity of their solar system disappear.
“After the red giant phase has ended and the sun has become a white dwarf, planetary orbits may become more chaotic, as the white dwarf sun has only half of its former mass, and the planets are now further away,” Hollands said.
This gravitational disruption increases the risk of planetary collisions, he added, which could fill the solar system with broken, rocky remnants of dead worlds. Larger, outer solar system planets (such as Jupiter, for example) can then use their own powerful gravity to fly the remnants out of orbit; some of them may end up close enough to the white dwarf sun to suck in and merge.
Although something in this line appears to have taken place around the four white dwarfs who studied Dutch and his colleagues, it is anyone’s guess whether the earth will ever reach a similar fate. According to co-author of the study Boris Gaensicke, also a professor at the University of Warwick, our planet is likely to be engulfed during the sun’s red giant phase leaving no elements for alien astronomers to detect.
However, this does not mean that the foreign telescopes come up empty handed.
“I would not bet that alien astronomers would detect the lithium of all the decayed Teslas in the sun-white dwarf,” Gaensicke told WordsSideKick. “But there’s a good chance they could see asteroids, comets, moons or even Mars being devoured.”
Originally published on Live Science.