Astronomers Might Have Found a Planet in Another Galaxy

Not that long ago,, astronomers weren’t sure that exoplanets even existed. Now we know that there are thousands of them and that most stars probably harbour exoplanets. There could be hundreds of billions of exoplanets in the Milky Way, by some estimates. So there’s no reason to think that stars in other galaxies don’t host planets.

But to find one of those planets in another galaxy? That is a significant scientific achievement.

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Moons are Planets too

What makes a planet a planet? The answer turns out to be rather contentious. The official definition of a planet, as defined by the International Astronomical Union (IAU) is that a planet must satisfy three conditions:

  1. It must orbit the Sun.
  2. It must be in hydrostatic equilibrium.
  3. It must have cleared its orbital neighborhood.

By this definition there are just eight planets in our solar system, most notably excluding Pluto. This has stirred all manner of controversy, even among astronomers. Several alternative definitions have been proposed, but a new study argues we should look to history for the solution.

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