White dwarfs are the “dead” stars of our galaxy, which are similar in size to the ground, but by weight – with the sun. They make up about 97% of the stellar population of our galaxy. These stars, reaching the completion of their life cycle, turn into dense balls, which makes the galaxy similar to a luminous cemetery.
The problem of the chemical composition of these star remains for a long time remained an unresolved mystery to astronomers. The presence on their surface of heavy metals, such as silicon, magnesium, and calcium, raised questions because theoretically, such elements should quickly fall to the nucleus of the star. “Heavy metals on the surface of the White Dwarf indicate that the star actively absorbs something,” explains Tatsuya Akiba, graduate student Jila.
In the new article in the journal Astrophysical Journal Letters, the team of Colorado and the University of Colorado in Boulder under the leadership of Professor Ann-Marie Mary and student the village of Makintire proposed an explanation. Using computer modeling, they found that during the formation of a white dwarf, an “impetus of birth” could occur due to the asymmetric loss of mass, which changed the movement of the star and the dynamics of its objects surrounding it. In 80% of cases, this led to the fact that the orbit of comets and asteroids became elongated and coincided, and about 40% of the absorbed planetesimals moved along retrograde orbits.
“This is the first time we see such long-term consequences of accretion,” says Madigan. These results not only help to understand why heavy metals are on the surface of a white dwarf but also open new details about the dynamics of such stars.
The results of the study are also important for understanding the formation and evolution of solar systems. According to Madigan, most planets will eventually find themselves in orbit in the White Dwarf, and perhaps up to 50% of these systems will be absorbed by their stars. “Now we have a mechanism explaining why this is happening,” she adds.
The village of Makintire emphasizes the importance of planetesimals to study other solar systems: “They help us learn more about the composition of the planets outside our solar region. White dwarfs are not only witnesses to the past but also the key to understanding the future.” These discoveries expand our knowledge about the chemistry and dynamics of space objects, providing new opportunities for studying the universe.