Astronomers Discovered A Moon Four Times The Size Of Earth – And It’s Much Closer Than You’d Think

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Image: Dan Durda via Science News
Image: Dan Durda via Science News

The Hubble Space Telescope is truly a wondrous thing. Having orbited the Earth since 2009, the images it has captured have been breathtaking. From star nurseries to distant galaxies, its lenses have allowed us to see into deepest space. And in 2017 its high-def range found something that no one had ever seen before…

Image: Till Credner
Image: Till Credner

Hubble had been watching a star in the Cygnus Constellation, about 8,000 light years away. The telescope’s target was the rather imaginatively named Kepler 1625. It was doing this because Columbia University’s Alex Teachey and David Kipping were waiting for an exoplanet – a planet in a different solar system – to pass in front of the star. Such a “transit” can be detected by a slight dip, or wobble, in the light coming from the Kepler 1625.

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Image: NASA, ESA
Image: NASA, ESA

As expected, the exoplanet – around the same the size of gas giant Jupiter – passed across the face of its star. However, the transit had started over an hour earlier than the astronomers had predicted. And this somewhat premature wobble was followed by a second, entirely unexpected, dip. Had the pair discovered, as they originally might have thought, a new exoplanet? Actually, no. What they’d witnessed was something that nobody else had ever seen.

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