On Friday (Sept. 20), students around the world will walk out of their classrooms and gather in coordinated protests to highlight the global crisis created by climate change.
Hundreds of orbiting comets and asteroids are thought to present some risk of colliding with Earth, but the threat is typically very small.
An ancient star in the Milky Way holds traces of another star that was among the oldest in the universe.
More than 4,000 photographers shot for the moon (and beyond) for the Astronomy Photographer of the Year competition in the U.K.
Signals written in elements from the early universe have revealed the oldest known merger between two galaxies, taking place less than a billion years after the Big Bang.
Three letters written by Einstein are up for auction, and they offer an intriguing view of his thoughts on quantum physics.
The former leader of the U.S. government's top-secret UFO program has stories to tell, and he is sharing some of them for the first time in a new documentary.
Between 2014 and 2015, seasoned pilots in the U.S. Navy experienced a number of harrowing encounters with UFOs during training missions in the U.S.
This is the strongest evidence to date of these oddball structures existing in the space between stars.
A black hole was recently the first to be captured in a close-up image, and in another first, it received a name that's a lot more interesting than the ones that usually identify black holes.
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