A small section of the expanding remains of the Veil Nebula, a massive star that exploded about 8,000 years ago. The entire nebula is 110 light-years across, covering six full moons on the sky as seen from Earth, and resides about 2,100 light-years away in the constellation Cygnus, the Swan. Image taken by NASA's Hubble Space Telescope. Released September 24, 2015. (Photo by Reuters/NASA/ESA/Hubble Heritage Team)

Tourists watch the Christmas Day sunrise behind Diamond Head from Waikiki Beach in Honolulu, Friday, December 25, 2015. (Photo by J. David Ake/AP Photo)

A male deer barks at dawn during the annual deer rutting season at Richmond Park in London, Britain, October 9, 2016. (Photo by Toby Melville/Reuters)

Workers lay railway track in a tunnel of the Crossrail project in Stepney, east London, Britain, November 16, 2016. Crossrail, which is Europe's largest construction project, is a railway link which will connect outlying areas to the east and west of London with tunnels under the centre of the capital. (Photo by Stefan Wermuth/Reuters)

Bluebella Lingerie advertising photo shoot, Oxford Circus, London, Great Britain on September 14, 2017. Bluebella has staged its most daring lingerie campaign yet, sending 19 models to strut their stuff in skimp smalls on one of London's busiest junctions. Bluebella organised the show early in the morning to minimise congestion ahead of London Fashion Week which starts on Friday 15th September. The “models” included a medical PA, a company boss, four students, two actors, a musician and two writers. (Photo by Cavendish Press/LESAUVAGE/Bluebella)

An Afghan boy looks through the scope of a toy gun, as other children ride on swings during the first day of the Muslim holiday of Eid al-Fitr, which marks the end of the holy month of Ramadan, in Kabul, Afghanistan June 25, 2017. (Photo by Omar Sobhani/Reuters)

Dancers perform on stage during the Crazy Horse Paris “Forever Crazy” Media Call at The MasterCard Theatres at Marina Bay Sands on October 11, 2017 in Singapore. Forever Crazy consists of a series of highly aesthetic and visual tableaus presented by a classically trained dancers clad only in textured lighting and projection. The show runs from 11 October 2017 till 22 October 2017 in Singapore. (Photo by Suhaimi Abdullah/Getty Images)

A man walks his dog as the sun sets in a park in Frankfurt, Germany, Monday, September 18, 2017. Cool damp weather is set to continue in this part of Germany for the next few days with temperatures in the mid teens Celsius. (Photo by Michael Probst/AP Photo)