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Possible reasons for a planet to fatally plunge into its host star include an orbital perturbation caused by a larger planet or another star passing uncomfortably close, destabilizing the planetary system, the researchers said.
“This really puts our fortuitous position in the universe into perspective,” 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 fact.”
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 away as 960 light years away. A light year is the distance light travels in one year, 5.9 trillion miles (9.5 trillion kilometers).
The researchers said that while their observations were more likely to indicate that entire planets were being ingested, it was possible that these were planetary building blocks consumed during the system’s planet-forming period.
In their death throes, our sun and other stars like it swell dramatically, devouring any planets with nearby orbits, before collapsing into a dense, scorched ash called a white dwarf.
“We know that all stars like the Sun will eventually become giant stars. The Sun’s envelope will expand and eventually engulf the Earth,” Ting said.
But all the stars in this study were in the prime of their lives, not approaching the end.
Instability in planetary systems may be more common than previously known, considering that about 8% of star pairs studied had a star apparently devouring a planet.
Most planetary systems should be stable because, as in our solar system, planets are primarily influenced by their host star, not their sister planets, Ting said.
“But in the case of other planetary systems with different initial conditions and configurations, this could break down, leading to very chaotic dynamics,” Ting added.
The study indicates that, Ting said, “a non-negligible fraction of planetary systems are in fact unstable, meaning that there are always planets that are ejected inward or outward.”
Since only a small fraction of these wayward planets could be devoured by their host star rather than simply wandering the cosmos, it is possible that there are more of these planetary exiles than previously suspected.
“Understanding which planetary systems are stable or not is a long-standing goal of planetary dynamics theorists,” Ting said.