Twin Stars and Cosmic Cannibalism

What’s in Today’s Article?

• Why in the News?
• Background
• About Twin Stars
• Possible Reasons Behind ‘Cosmic Cannibalism’ & Significance

Why in the News?

Recently, researchers analyzed 91 star pairs from the same birth cloud, sharing similar sizes and compositions.

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Background

• The planetary system that includes Earth and its sibling planets orbiting the sun has been remarkably stable during its roughly 4.5 billion years of existence.
• But not all planetary systems are stable, as shown in a new study involving “twin” stars.
• An international research team used three huge telescopes to look at 91 pairs of twin stars and found some showed evidence of ‘ingesting’ planets.
• Scientists had presumed the twin stars would have identical compositions but surprisingly found that around eight percent of them differ from the others.
• This difference lies in one of the stars showing a tendency to ‘devour’ planets or planetary material.
• The researchers found this phenomenon of cosmic cannibalism appearing in around 7 of the 91 pairs of twin stars they looked at.
• All these stars were also in their prime of life – being so-called ‘main sequence’ stars – rather than stars in their final phases of life such as red giants.

About Twin Stars

• The study looked at pairs of stars that formed within the same interstellar cloud of gas and dust – so-called co-natal stars – giving them the same chemical makeup, and were of roughly equal mass and age. These are the “twins.”
• While the pairs are moving together in the same direction within the Milky Way Galaxy, they are not binary systems of two stars gravitationally bound to each other.
• A star’s chemical composition changes when it engulfs a planet because it incorporates the elements that made up the doomed world.
• The researchers looked for stars that differed from their twin because they had higher amounts of tell-tale elements like iron, nickel or titanium indicating remnants of a rocky planet, relative to certain other elements.
• In seven of the pairs, one of the two stars bore evidence of planetary ingestion.

Possible Reasons Behind ‘Cosmic Cannibalism’& Significance

• 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.
  • 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.
• The study indicated that a non-negligible fraction of planetary systems is 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 estimated.

Q1) What is meant by Binary Star?

A binary star or binary star system is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called visual binaries.

Q2) What is meant by Intergalactic Space?

Intergalactic Space is the region of physical space that exists between galaxies.