Silhouetted Gallery

Northern lights

Northern lights. The Northern Lights are created as electrically charged particles from the Solar wind are pulled in toward the magnetic poles by the Earth's magnetic field. As these particles collide with the atoms of gas in the ionosphere about 80km above the ground, they give the atoms energy and they become excited'. The atoms spontaneously release this energy in discrete amounts, resulting in particular colours of light being emitted. Photographed in the Swedish Arctic

© Jeremy Walker

Aurora borealis

Aurora borealis seen over trees through a fish-eye lens, with an observer at far right. This light display (the northern lights) is seen in the night sky at high latitudes. It occurs when charged and energetic particles from the Sun (the solar wind) are drawn by Earth's magnetic field to the polar regions. Hundreds of kilometres up, they collide with gas molecules and atoms, causing them to emit light. Photographed over Alaska, USA, in 2000

© CHRIS MADELEY/SCIENCE PHOTO LIBRARY

Overlapping galaxies, HST image

Overlapping galaxies. Hubble Space Telescope (HST) image of the overlapping galaxies known as 2MASX J00482185-2507365. The two objects are both spiral galaxies, with the outer rim of a small, foreground galaxy (upper right) silhouetted in front of a larger background galaxy (centre left). Dust lanes in the smaller galaxy are seen in front of the larger one. 2MASX J00482185-2507365 is located in the constellation of Sculptor and is around 780 million light years from Earth. The area seen here is around 180, 000 light years across. This image was obtained in 2006, using HST's Advanced Camera for Surveys (ACS)

© NASA/ESA/STSCI/HUBBLE HERITAGE TEAM/SCIENCE PHOTO LIBRARY