Mar 17, 2021 - Science

New study says first-known interstellar object was a planet chunk

An artist's rendition of Oumuamua, which one Axios visuals editor referred to as a "steak in space."
An artist's rendition of Oumuamua, which one Axios visuals editor referred to as a "steak in space." Credit: William Hartmann

A new study concludes that the first-known interstellar object to pass through our solar system is probably a piece from another planet.

The big picture: The finding throws cold water on the theory — raised by one prominent astrophysicist — that the object was really an alien artifact, but it will help scientists learn about the makeup of planets beyond our corner of the galaxy.

What's happening: In a pair of papers published Wednesday, researchers from Arizona State University posit an explanation for Oumuamua, a flat, comet-like object that was discovered hurtling through our solar system in 2017.

  • They argue the object is a chunk of an "exo-Pluto" — a Pluto-like planet from another solar system.
  • Oumuamua was likely knocked off the surface of the exoplanet by an impact half a billion years ago and thrown out of its parent system, before wandering through ours.

Background: Oumuamua puzzled scientists when it was first discovered because it seemed like a comet but lacked some of the usual traits, like the detectable escaping gas that makes up a comet's tail.

  • Harvard astrophysicist Avi Loeb even posited in a book published earlier this year that "the simplest explanation for [Oumuamua's] peculiarities is that the object was created by an intelligent civilization not of this Earth."

Reality check: The extreme skepticism with which Loeb's theories were met by the mainstream scientific community now seems warranted.

Our thought bubble: "Oumuamua likely won’t be the last interstellar visitor scientists find, so this kind of research is essential for placing the strange object in context with our solar system and others," my Axios Space colleague Miriam Kramer notes.

The bottom line: As Miriam — Axios' own Agent Scully — has repeatedly written: "It's never aliens."

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