On January 27

Astronomers documented H1504+65, a white dwarf in Ursa Minor (chart pictured) with the hottest surface temperature known at the time, at 200,000 kelvins (360,000 °F).

Arab Spring: The Yemeni Revolution began as more than 16,000 protesters demonstrated in Sanaa to demand governmental changes.

Porfirio Lobo Sosa became the new president of Honduras, ending a constitutional crisis that had begun in 2009 when Manuel Zelaya was forcibly removed from office.

The first selections for the United States National Recording Registry were announced by the Library of Congress.

Mahamane Ousmane, the first democratically elected president of Niger, was deposed by Colonel Ibrahim Baré Maïnassara in a military coup d'état.

Six American diplomats who had evaded capture in the Iran hostage crisis escaped with the help of Canadian government officials to Zürich, Switzerland.

A fire during a launch simulation for the Apollo 1 mission at Cape Kennedy killed astronauts Gus Grissom, Ed White and Roger Chaffee.

South Vietnamese prime minister Trần Văn Hương was removed by the military junta of Nguyễn Khánh.

The Soviet Red Army liberated about 7,000 prisoners left behind by the Nazis in Auschwitz concentration camp.

A contaminated diphtheria vaccine was used in an Australian immunisation program, leading to the deaths of twelve children and the suspension of immunisation programs in several countries.

Former members of the overthrown Tokugawa shogunate proclaimed Japan's second-largest island, Hokkaido, to be the independent Republic of Ezo.

On the advice of John C. Calhoun, President James Monroe asked Congress to organize Indian Territory (map pictured) west of the Mississippi River, laying the groundwork for Indian removal in the United States.

French Revolutionary Wars: In the Macau Incident, French and Spanish warships encountered a British Royal Navy escort squadron in the Wanshan Archipelago; subsequent events, including which side retreated, were disputed by the commanders present.

The University of Georgia, the oldest state-chartered public university in the United States, was founded.

J. S. Bach led the first performance of Alles nur nach Gottes Willen, BWV 72, concluding his third Christmas season in Leipzig on the Third Sunday after Epiphany.

Clement VI issued the papal bull Unigenitus, justifying the power of the pope and the use of indulgences.

The brothers Stephen and Constantine Lekapenos, having deposed their father as Byzantine emperor a few weeks earlier, were themselves overthrown by Constantine VII, their co-emperor.

Trajan succeeded his adoptive father Nerva as Roman emperor; the Roman Empire reached its maximum extent under his rule.