Shan boys pray before they have their heads shaved in anticipation of their ordination in the Poy Song Long Ceremony at Wat Pa Pao in Chiang Mai, Thailand on April 3, 2018. Poy Sang Long (“The Festival of the Crystal Sons”) is a ceremony that marks a rite of passage among the Buddhist Shan people in Myanmar and northern Thailand. Boys between seven and fourteen years of age are ordained as Buddhist novices during a three day ceremony. Before the ceremony starts the boys have their heads shaved. (Photo by Jack Kurtz/ZUMA Wire/Rex Features/Shutterstock)

A young girl takes selfie with Easter rabbit sculpture during the Easter eggs (Pysanka) and rabbit exhibition in front of St. Sophia Cathedral in Kiev, Ukraine, 05 April 2018. Ukrainians will mark Orthodox Easter on 08 April 2018, according to Julian calendar. (Photo by Sergey Dolzhenko/EPA/EFE/Rex Features/Shutterstock)

A participant with a face painted as popular Mexican figure “Catrina” attends the Day of the Dead event at a National house for Mexican fans in central Moscow, a host city for the 2018 FIFA World Cup, Russia June 29, 2018. (Photo by Sergei Karpukhin/Reuters)

A woman cools off from the extreme heat from an opened fire hydrant in Brooklyn, New York on July 2, 2018. The highest temperature reached 35 degrees Celsius in New York City on Monday as a result of a prolonged heat wave. (Photo by Shannon Stapleton/Reuters)

Festivalgoers dance during the Balaton Sound music festival in Zamardi, Hungary, July 5, 2018. Balaton Sound is one of Europe's largest open air electronic music festivals. Held annually since 2007 on the southern bank of Lake Balaton, Hungary, it features live acts and DJ's from all around the world, from established artists to new names. The event was co-created by the organizers of Sziget Festival. (Photo by Bernadett Szabo/Reuters)

England fan celebrates on top of an ambulance after England' s win over Sweden in the Russia 2018 World Cup quarter- final football match, in London on July 7, 2018. (Photo by Henry Nicholls/Reuters)

Ministry of Defence handout photo of Chinooks from RAF Odiham as they take part in the Royal Air Force flypast over central London to mark the centenary of the RAF on Tuesday, July 10, 2018. (Photo by SAC Pippa Fowles (RAF)/PA Wire)

The competition is run by Royal Observatory Greenwich sponsored by Insight Investment and in association with BBC Sky at Night Magazine. This year astrophotographers from 91 countries sent in more than 4,200 spectacular entries. Here: The Milky Way rises above an isolated lighthouse in Tasmania. Shot by James Stone of Australia. (Photo by James Stone/Astronomy Photographer of the Year 2018)