Luxembourg City, the capital of Luxembourg — shown here in 2012 — mixes the medieval and the modern. The tiny European nation is making a serious bid for the futuristic, too. Loop Images/UIG via Getty Images hide caption

toggle caption Loop Images/UIG via Getty Images

(Left) Bob Ebeling in his home in Brigham City, Utah. (Right) The Challenger lifts off on Jan. 28, 1986, from a launchpad at Kennedy Space Center, 73 seconds before an explosion killed its crew of seven. (Left) Howard Berkes/NPR; (Right) Bob Pearson/AFP/Getty Images hide caption

toggle caption (Left) Howard Berkes/NPR; (Right) Bob Pearson/AFP/Getty Images

A view from Earth of a slender crescent moon in close proximity to the two brightest planets in the sky, Venus and Jupiter. Justin Lane/epa/Corbis hide caption

toggle caption Justin Lane/epa/Corbis

A NASA team has attached nearly all of the hexagonal segments that will together make the primary mirror for the James Webb Space Telescope (pictured are practice segments). Chris Gunn/NASA hide caption

toggle caption Chris Gunn/NASA

The imagined view from Planet Nine back toward the sun. Astronomers think the huge, distant planet is likely gaseous, similar to Uranus and Neptune. Caltech/R. Hurt (IPAC) hide caption

toggle caption Caltech/R. Hurt (IPAC)

An artist's impression of the superluminous supernova as it would appear from a planet in the same galaxy, about 10,000 light-years away. The exploding star is 570 billion times brighter than our sun. Jin Ma/Beijing Planetarium/Science hide caption

toggle caption Jin Ma/Beijing Planetarium/Science

NPR thanks our sponsors

Become an NPR sponsor