Rioters scuffle with police on a street in Mongkok district of Hong Kong, Tuesday, February 9, 2016. Rioters clashed with police overnight and into the early hours of Tuesday in a crowded area of Kowloon. The unrest started when local authorities tried to prevent street food sellers from operating on Monday night. Activists who are dissatisfied with Hong Kong's administration took part in the clashes, local media reports said. (Photo by Kin Cheung/AP Photo)

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. (Photo by Reuters/NASA/ESA/Hubble)

A model slips on the runway while parading an outfit by Australian designer Toni Maticevski at Fashion Week Australia in Sydney on May 15, 2016. (Photo by William West/AFP Photo)

Workers clean empty cooking oil containers at a roadside recycling workshop in Kolkata, India, July 13, 2016. (Photo by Rupak De Chowdhuri/Reuters)

Cambodian children sleep on a pavement at a park in Phnom Penh on July 8, 2016. (Photo by Tang Chhin Sothy/AFP Photo)

2016 Rio Olympics, Gymnastics training, Rio Olympic Arena, Rio de Janeiro, Brazil on August 4, 2016. Close up of the feet of Rebecca Downie (GBR) of United Kingdom as she trains on the beam. (Photo by Dylan Martinez/Reuters)

Revellers dance at Notting Hill Carnival on August 29, 2016 in London, England. The Notting Hill Carnival, which has taken place annually since 1964, is expected to attract over a million people. The two-day event, started by members of the Afro-Caribbean community, sees costumed performers take to the streets in a parade and dozens of sound systems set up around the Notting Hill streets. (Photo by Jack Taylor/Getty Images)

Baby giraffe of Niger (Giraffa Camelopardalis) “Kenai” (R), born on August 25, 2016, kisses his mother “Dioni” on August 31, 2016 at the zoo of La Fleche, northwestern France. (Photo by Jean-Francois Monier/AFP Photo)