Glow 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

The massive galaxy cluster MACS J0717

This composite image shows the massive galaxy cluster MACS J0717.5+3745 (MACS J0717, for short), where four separate galaxy clusters have been involved in a collision, the first time such a phenomenon has been documented. Hot gas is shown in an image from the Chandra X-ray Observatory, and galaxies are shown in an optical image from the Hubble Space Telescope. The hot gas is color-coded to show temperature, where the coolest gas is reddish purple, the hottest gas is blue, and the temperatures in between are purple. MACS J0717 is located about 5.4 billion light-years from Earth. It is one of the most complex galaxy clusters ever seen.
The repeated collisions in MACS J0717 are caused by a 13-million-light-year-long stream of galaxies, gas, and dark matter, known as a filament, pouring into a region already full of matter. A collision between the gas in two or more clusters causes the hot gas to slow down. However, the massive and compact galaxies do not slow down as much as the gas does, and so move ahead of it. Therefore, the speed and direction of each cluster's motion, perpendicular to the line of sight, can be estimated by studying the offset between the average position of the galaxies and the peak in the hot gas

© Stocktrek Images

Aurora borealis and Moon

Aurora borealis and Moon over mountains and trees by a river. This coloured light display (the northern lights) is visible 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 by the Koyukuk River, near Wiseman, Alaska, USA

© CHRIS MADELEY/SCIENCE PHOTO LIBRARY