When stars run out of fuel and reach the end of their lives, the largest explode in huge supernovae. But smaller stars undergo another change in which they shed parts of their masses, creating a planetary nebula around them, leaving behind a small, dense core called a white dwarf. Like most stars, our sun will eventually become a white dwarf, glowing with waste heat but no longer producing energy through fusion.
Even though he is no longer active in the field of fusion, a white dwarf is still a formidable beast. Because the remnant of the star collapses into a small core, it is extremely dense, and the gravity of this core can wreak havoc on the objects around it. Recently, the Hubble Space Telescope discovered a case of cosmic cannibalism, in which a white dwarf consumed rocky and icy material from its environment.
The white dwarf, named G238-44, is the first to be observed accreting both rocky metallic material and icy material, which is important because these are the main components from which planets are formed. Studying this white dwarf could therefore help researchers learn more about the formation of planetary systems.
Scientists know that when stars swell to become red giants before losing mass and becoming white dwarfs, they have a dramatic impact on all the planets in their vicinity. And because the white dwarf studied by Hubble attracts matter associated with planetary formation, including elements such as nitrogen, oxygen, magnesium, silicon and iron, the researchers can observe the mix of elements that would have gone to planets when they were first formed.
In addition, the fact that the white dwarf attracts icy bodies suggests that comets are common in planetary systems, supporting the theory that water could be brought to early Earth by a comet or asteroid.
“Life as we know it requires a rocky planet covered with a variety of elements such as carbon, nitrogen and oxygen,” said one of the researchers, Benjamin Zuckerman, in a statement. pronunciation† “The abundance of elements we see on this white dwarf appears to require both a rocky and a volatile-rich parent body — the first example we’ve found in studies of hundreds of white dwarfs.”