Vintage American history photo of a nuclear weapon test by the American military at Bikini Atoll, Micronesia on July 25, 1946. The explosion was part of Operation Crossroads. John Parrot/Stocktrek Images/Getty Images hide caption

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John Parrot/Stocktrek Images/Getty Images

President Barack Obama speaks during the dedication ceremony for the Smithsonian Museum of African American History and Culture in Washington, DC, on Sept. 24, 2016. Pablo Martinez Monsivais/AP hide caption

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Pablo Martinez Monsivais/AP

From left, Octavia Spencer, Janelle Monae and Taraji P. Henson accept the award for outstanding performance by a cast in a motion picture for Hidden Figures at the 23rd annual Screen Actors Guild Awards on Jan. 29 in Los Angeles. Chris Pizzello/Invision/AP hide caption

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Chris Pizzello/Invision/AP

This artist's impression shows the surroundings of a supermassive black hole, typical of that found at the heart of many galaxies. The black hole itself is surrounded by a brilliant accretion disc of very hot, infalling material and, further out, a dusty torus. There are also often high-speed jets of material ejected at the black hole's poles that can extend huge distances into space. L. Calçada/ESO hide caption

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L. Calçada/ESO

This artist's view shows an exoplanet orbiting the young star Beta Pictoris. The exoplanet has an eight-hour day — and a much faster rotation than any planet in the solar system. L. Calçada/N. Risinger/ESO hide caption

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L. Calçada/N. Risinger/ESO

Taking Stock In The Search For Aliens

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President Donald Trump is joined by the Congressional leadership and his family before formally signing his cabinet nominations into law on Jan. 20 in the President's Room of the Senate on Capitol Hill in Washington. From left are, Vice President Mike Pence, the president's wife Melania Trump, their son Barron Trump, and House Speaker Paul Ryan. J. Scott Applewhite/AP hide caption

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J. Scott Applewhite/AP

Cajal summarizes many of the properties of astrocytes in this drawing of the hippocampus of a man three hours after death. Courtesy Instituto Cajal del Consjo Superior de Investigaciones Científicas, Madrid, © 2017 CSIC hide caption

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Courtesy Instituto Cajal del Consjo Superior de Investigaciones Científicas, Madrid, © 2017 CSIC