A Somali police officer arrests a suspected rebel member of the al Qaeda-affiliated al Shabaab among beach goers in Mogadishu. Al Shabaab claimed responsibility for today's pre-dawn attack on a Kenyan university campus near the Somali border. The following gallery examines who is al Shabaab. Here: Somali police officer (R) arrests a suspected rebel member (L) of the Al Qaeda-affiliated al Shabaab among beach goers at the Lido beach north of Somalia's capital Mogadishu March 23, 2012. (Photo by Feisal Omar/Reuters)

A cat sits in the flooding waters from Hurricane Matthew in downtown Nichols, South Carolina, October 10, 2016. (Photo by Randall Hill/Reuters)

A female member of Romania's military adjusts her hat before taking part in the national day military parade in Bucharest, Romania, Friday, December 1, 2017. Thousands of Romanian troops staged a military parade to celebrate Romania's national day, but key politicians didn't attend, signaling tensions between the president and the ruling left-wing coalition over plans to revamp the justice system. (Photo by Vadim Ghirda/AP Photo)

A man and his cat rest in the street after an earthquake on May 22, 2021 in Dali, Yunnan Province of China. According to the China Earthquake Networks Center, a 5.6-magnitude earthquake jolted Yangbi Yi autonomous county in Dali Bai autonomous prefecture, Southwest China's Yunnan province on Friday evening. (Photo by Liu Ranyang/China News Service via Getty Images)

A man runs to take cover as supporters of a Shiite group allied with Hezbollah fire weapons during armed clashes that erupted during a protest in the southern Beirut suburb of Dahiyeh, Lebanon, Thursday, Octoner 14, 2021. It was not immediately clear what triggered the gunfire, but tensions were high along a former civil war front-line between Muslim Shiite and Christian areas. (Photo by Hassan Ammar/AP Photo)

Burning candles illuminate graves as a Bangladeshi man observes a contemplative moment on All Souls' Day at the Dhaka Christian Cemetery at Wari in Dhaka, Bangladesh, 02 November 2021. People on All Saints Day and All Souls Day pay respect to deceased relatives and loved ones by placing flowers on their tombs or maintaining their graves and lighting candles. (Photo by Monirul Alam/EPA/EFE)

A government awareness poster for wearing surgical masks is seen reflected and upside-down in the Dambovita river in Bucharest, Romania, 19 November 2020. The poster, depicting a man wearing a surgical mask, reads: “I WEAR A MASK BECAUSE I KNOW THAT ONLY TOGETHER WE WILL SUCCEED!”. As the number of COVID-19 infections increased, authorities decided that wearing a protective mask should become mandatory at all times in all public places. (Photo by Robert Ghement/EPA/EFE)

M42 Subtle V1 cropped. One of the most well-known astronomical objects in our universe is the Orion Nebula and this image depicts the wider region of the Orion Molecular Cloud Complex that is its home. This complex also includes another popular target for astrophotographers, the Horsehead Nebula, as well as Barnard’s Loop and the Running Man Nebula, which can be seen to the left of this photograph. (Photo by Patrick Gilliland)