Possible reasons for a planet making a death plunge into its host star include an orbital disturbance caused by a larger planet, or another star passing uncomfortably close, destabilizing the planetary system, the researchers said.
“This really puts into perspective our fortuitous position in the universe,” said astrophysicist and study co-author Yuan-Sen Ting of the Australian National University and Ohio State University. “The stability of a planetary system like the solar system is not a given.”
The researchers used the European Space Agency’s Gaia space observatory to identify the twins and used telescopes in Chile and Hawaii to determine their composition. The stars were as close as 70 light years from our solar system and as far as 960 light years away. A light year is the distance light travels in a year, 5.9 trillion miles (9.5 trillion km).
The researchers said while it is most likely that their observations signaled whole planets being ingested, it was possible it was planetary building blocks consumed during the system’s period of planet formation.
In their death throes, our sun and other stars like it dramatically puff up, ingesting any planets with close orbits, before collapsing into a dense, burned-out cinder called a white dwarf.
“We know that all stars like the sun will eventually become giant stars. The envelope of the sun will expand and eventually swallow Earth,” Ting said.
But the stars in this study all were in the prime of their life, not nearing the end.
Instability in planetary systems may be more common than previously known, considering that about 8% of the stellar pairs studied had one star that apparently devoured a planet.
Most planetary systems should be stable because, as in our solar system, the planets are under the influence mainly of their host star, not their sibling planets, Ting said.
“But for other planetary systems with different initial conditions and configurations, this might break down, leading to very chaotic dynamics,” Ting added.
The study indicates that, Ting said, “a non-negligible fraction of planetary systems are indeed unstable, meaning there are always planets being ejected in or out.”
Given that only a small fraction of these wayward planets might actually be gulped by their host star rather than simply wandering the cosmos, there may be more of these planetary exiles than previously suspected.
“Understanding which planetary systems are stable or not is a long-time goal of planetary dynamics theorists,” said Ting.
Shambhu Kumar is a science communicator, making complex scientific topics accessible to all. His articles explore breakthroughs in various scientific disciplines, from space exploration to cutting-edge research.
