Happy Astronomy Day!

No, that's not a downpour of lightsabers—but it's no typical night sky either. Stargazing here at Paranal Observatory, on a mountaintop in Chile's desolate Atacama Desert, you'll get one of the clearest possible naked-eye views of the southern skies. This 'lightsaber' effect comes from the photo's long exposure: What we're seeing is these stars' paths as they track across the night sky due to our planet's rotation. Colour differences in stars are generally visible to the naked eye, so remember this next time you go stargazing: The chilliest stars (around 2,700 degrees Celsius) appear red, while the hottest (tens of thousands of degrees) appear blue or nearly white.
© Matteo Omied/Alamy