Study of ‘binary’ stars finds evidence of planetary engulfing

In seven of the pairs, one of the two stars has evidence of planetary engulfment. (representative)

Washington:

The planetary system, including the Earth and its sibling planets orbiting the Sun, has been remarkably stable throughout its approximately 4.5 billion years of existence. But not all planetary systems are so lucky, as a new study involving “binary” stars shows.

An examination of 91 pairs of stars matched in size and chemical composition revealed a surprising number of stars showing signs of engulfing planets, likely after planets were sent out of stable orbits for a variety of reasons, scientists said Wednesday.

The study looked at pairs of stars that formed in the same interstellar cloud of gas and dust – so-called costars – that have the same chemical composition and are roughly equal in mass and age. This is “twin”. Although these two pairs of stars move together in the same direction within our galaxy, they are not a binary system consisting of two stars gravitationally bound to each other.

When a star engulfs a planet, its chemical composition changes because it contains the elements that made up this doomed world. The researchers looked for stars that differed from the twins because they contained more elements such as iron, nickel or titanium relative to certain other elements, indicating the remnants of rocky planets.

“It’s the difference in elemental abundance between two stars in a contemporaneous system,” said astronomer Fan Liu of Monash University in Australia and lead author of the study published in the journal Nature .

In seven of the pairs, one of the two stars has evidence of planetary engulfment.

Possible causes of a planet falling into its host star and dying include orbital perturbations caused by a larger planet, or another star coming too close, destabilizing the planetary system, the researchers said.

“This really allows us to see our fortuitous place in the universe,” said study co-author Yuansen Ding, an astrophysicist at Australian National University and Ohio State University. “The stability of a planetary system like our own is not a given. “

Researchers used the European Space Agency’s Gaia space observatory to identify the twins and telescopes in Chile and Hawaii to determine their composition. These stars range from as close as 70 light-years to our solar system and as far away as 960 light-years. A light year is the distance that light travels in one year, or 5.9 trillion miles (9.5 trillion kilometers).

The researchers say that while their observations most likely indicate the engulfment of an entire planet, it’s also possible that planetary building blocks were consumed during the system’s planet formation.

In its death throes, our sun and other stars like it expand dramatically, swallowing up any planets in closer orbit before collapsing into dense charred cinders called white dwarfs.

“We know that all stars like the Sun will eventually become giant stars. The Sun’s envelope will expand and eventually engulf the Earth,” Ding said.

But the stars in the study were in the prime of their lives, not near the end.

Considering that about 8% of the star pairs studied had one star apparently engulfing a planet, instability in planetary systems may be more common than previously known.

Most planetary systems should be stable, Ding said, because, like in our solar system, planets are primarily affected by their host stars, not their sibling planets.

“But for other planetary systems with different initial conditions and configurations, this can break down, leading to very chaotic dynamics,” Ding added.

Ding said the study shows that “a non-negligible portion of planetary systems are indeed unstable, meaning there are always planets being ejected or ejected.”

Given that only a small percentage of these wayward planets may actually be swallowed by their host stars, rather than simply wandering around the universe, there may be more of these planetary exiles than previously suspected.

“Understanding which planetary systems are stable or unstable is a long-term goal for planetary dynamics theorists,” Ding said.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)