This is the amazing moment a heroic hippo saved a gnu from certain death. After being bitten by a crocodile, the large antelope is seen being dragged slowly under the water. But in a miraculous turn of events, a nearby hippo is seen making its way across the water to help the animal in its hour of need. Photo: One of the biggest hippos protects the gnu as it makes its way back to the shoreline, guarding it from any further attacks. (Photo by Vadim Onishchenko/Caters News)

Photographer and editor with Reuters for 22 years, Andrew Winning has died of brain cancer at the age of 49. Here: Elite special police run for cover after gunfire was heard from inside the Japanese ambassador's residence in Lima, Peru, January 27, 1997. At the moment the shots were fired, police were parading past the residence in a show of force, and helicopters were flying above. Earlier, several armored personnel carriers rolled past the compound. Tupac Amaru rebels had seized the diplomatic compound December 17 and held 72 hostages. (Photo by Andrew Winning/Reuters)

The Northern Lights glow green in a spectacular light show above a field of trees frozen solid with snow. (Photo by Jaak Sarv/Solent News & Photo Agency)

The supermoon rises behind Glastonbury Tor on September 27, 2015 in Glastonbury, England. Tonight's supermoon, so called because it is the closet full moon to the Earth this year, is particularly rare as it coincides with a lunar eclipse, a combination that has not happened since 1982 and won't happen again until 2033. (Photo by Matt Cardy/Getty Images)

Gorgeous galaxies and stunning stars make up this selection of pictures from the shortlisted entries for this year’s Insight Astronomy Photographer of the Year award. The winners will be announced on 15 September, and an exhibition of the winning images will be will be displayed in a free exhibition at the Royal Observatory Greenwich’s Astronomy Centre from 17 September. Here: “Seven Magic Points”. The rusty red swirls of the circular, iron sculpture Seven Magic Points in Brattebergan, Norway mirror the rippling aurora above. (Photo by Rune Engebø/Royal Observatory Greenwich’s Astronomy Photographer of the Year 2016/National Maritime Museum)

“Aurora over a glacier lagoon”. A vivid green overheaded aurrora pictured in Iceland's Vatnajokull National Park reflected almost symetrically in Jokulsrlon Glacier lagoon. A complete lack of wind and currrent combin in this sheltred lagoon scene to crete an arresting mirror effect giving the image a sensation of utter stillness. Despite theis there is motion on a suprising scale, as the loops and arcs of the aurora are shaped by the shifting forces of the Earth's magnetic field. James Woodend of Great Britain won the grand prize with the image, beating out more than 2,500 other entries. The Astronomy Photographer of the Year 2014 contest is judged by the Royal Observatory Greenwich and BBC Sky at Night magazine. (Photo by James Woodend/The Astronomy Photographer of the Year 2014 Contest)

Hundreds of festive, adorable canines and their owners took part in the annual “A Very Corgi Howloween” costume walk Saturday, October 25, 2014, at Green Lake in Seattle, Wash. The walk was put on by the Seattle-local “Corgi's R Us” MeetUp group. (Photo by Jordan Stead/AP Photo/Seattlepi.com)

Mount Sinabung volcano erupts, as seen from Tiga Pancur village, Karo Regency in Indonesia's North Sumatra province, in this October 8, 2014 file photo. (Photo by Y. T. Haryono/Reuters)