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)

Sunday night, Lauren Watts searches for her dog in Mayflower, Arkansas., after a tornado struck the town. (Photo by Benjamin Krain/The Arkansas Democrat-Gazette)

“Kilauea Rules”. The most extreme place we put ours kayakers to paddle till now. Photo location: Big Island, Hawaii. (Photo and caption by Alexandre Socci/National Geographic Photo Contest)

Gertrude “Billie” Murphy, 22, is brought in for questioning in the murder case of Michael Stopec, who was shot and killed in an apartment hotel, circa July 1927. Murphy had been friends of the married Stopec and his suspected killer Henry Guardino, 31. It is said that Stopec and Guardino were “bitter rivals for the favor of Billie” and that Murphy had tired of Guardino and was going to stay with Stopec. Murphy was also married to a man in the Joliet penitentiary. (Photo by Chicago Herald & Examiner Historical Photo)

North Korea has closed its borders in fear of the spread of the Ebola virus. But at a time when the secretive state was still welcoming tourists, former aid worker Andrew Macleod made the journey to the repressive nation. Andrew's holiday snaps and camera footage provide a unique insight into the reclusive country, where he came across deserted motorways, metro stations plastered with propaganda and attractive border guards. Here: a female traffic police officer in the snow in February 2013, in Pyongyang, North Korea. (Photo by Andrew Macleod/Barcroft Media)

Three prostitutes lean out of a window in Santiago, Chile, in an attempt to entice customers inside, circa 1950. (Photo by Three Lions/Getty Images)

St Louis County police officers arrest an anti-police demonstrator in Ferguson, Missouri August 10, 2015. Dozens of protesters were arrested on Monday afternoon after blocking rush-hour traffic on Interstate 70 a few miles (km) from Ferguson, Missouri, during demonstrations over the police shooting of an unarmed black man a year ago, according to a Reuters witness. (Photo by Lucas Jackson/Reuters)

Men cover their heads from the sun while riding on a motorcycle during a hot day in Cairo, Egypt, August 17, 2015. A heatwave killed at least 61 people across Egypt from Sunday to Tuesday and caused nearly 600 people to be admitted to hospital, Egypt's health ministry said on state news agency MENA on Wednesday. (Photo by Amr Abdallah Dalsh/Reuters)