A guiding star

A solitary laser beam cuts through the night sky. It streaks upwards from Unit Telescope 4 of ESO's Very Large Telescope, located at Paranal Observatory in Chile. The two Magellanic Clouds are visible to the left of the beam as faint, fuzzy patches against the starry background. The particularly bright star to the right of the beam is Canopus, the second brightest star in our night sky after Sirius.

When ground-based telescopes view stars, the light they collect must travel through the layers of our atmosphere. The same water vapour, pollution, and turbulence that causes the stars in the sky to twinkle also result in blurred images — so in comes a technique known as adaptive optics.

Adaptive optics systems use sophisticated deformable mirrors to counteract the negative effects of our atmosphere. The laser shines up into the sky, creating an artificial star about 90 kilometres from the ground.  Astronomers can then measure how this fake star twinkles in time, and can correct for this distortion. Telescopes that use adaptive optics can produce images sharper than those from space-based telescopes at certain wavelengths.

A similar system is to be installed on the European Extremely Large Telescope (E-ELT). The E-ELT will have six lasers, which will provide even higher-quality astronomical images over a much larger field-of-view — and provide more opportunities for striking snaps like this one.

This image was taken on 4 March 2013 from the Visible and Infrared Survey Telescope for Astronomy (VISTA) platform by ESO photo ambassador Julien Girard, a staff astronomer at ESO. It was taken using a point and shoot compact camera which nowadays can perform night photography.