The competition, which is run by the Royal Observatory Greenwich in association with BBC Sky at Night Magazine, is now in its sixth year and has received over 2,500 entries. Photo: Centre of the Heart Nebula by Ivan Eder (Hungary). Situated 7500 light years away in the “W”-shaped constellation of Cassiopeia, the Heart Nebula is a vast region of glowing gas, energized by a cluster of young stars at its centre. The image depicts the central region, where dust clouds are being eroded and moulded into rugged shapes by the searing cosmic radiation. (Photo by Ivan Eder)

Women dressed in folk costumes take part in a traditional wedding ceremony in the village of Galicnik, west of Macedonia's capital Skopje, July 12, 2014. The Galicnik Wedding, a three-day traditional Macedonian wedding celebration held each “Petrovden” or St. Peter's Day, involves traditional customs, costumes, and rituals and dances that have been passed down over the centuries. (Photo by Ognen Teofilovski/Reuters)

A boy looks for sellable materials close to the burning garbage in the permanent waste land under Sylhet City Corporation for a living, on January 15, 2015. (Photo by Md. Akhlas Uddin/Pacific Press)

A woman takes a selfie next to a model of Thor during the Middle East Film & Comic Con (MEFCC) in Dubai, United Arab Emirates, Saturday, April 11, 2015. (Photo by Kamran Jebreili/AP Photo)

An Afghan teacher, in brown, helps school children run from the site of clashes near the Pakistan consulate in Jalalabad, capital of Nangarhar province, Afghanistan, Wednesday, January 13, 2016. Several members of the Afghan security forces were killed Wednesday after unidentified gunmen attacked the Pakistani consulate in a volatile eastern province, an official said on Wednesday. (Photo by Mohammad Anwar Danishyar/AP Photos)

A woman carries a bag with a baby while being evacuated by local emergencies ministry members in Donetsk, Ukraine, February 2, 2017. (Photo by Alexander Ermochenko/Reuters)

Nicki Minaj attends the Haider Ackermann show as part of the Paris Fashion Week Womenswear Fall/Winter 2017/2018 on March 4, 2017 in Paris, France. (Photo by Swan Gallet/WWD/Rex Features/Shutterstock)

A girl collects water lily flowers at a pond in Kampong Speu province Cambodia, March 24, 2017. Picture taken March 24, 2017. (Photo by Samrang Pring/Reuters)