Neil deGrasse Tyson

Astrophysicist/author Neil deGrasse Tyson (R) shares a laugh at Comic-Con in San Diego, Calif. in 2013.

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As the director of the Hayden Planetarium at New York City's American Museum of Natural History, Neil deGrasse Tyson can be found encouraging children to explore the world around them. It's a nice turnaround since a visit to a planetarium in the mid-1960s ignited a 9-year-old Tyson's own passion for the stars.

Tyson is an astrophysicist by trade and science enthusiast by nature, and is considered one of the driving forces behind Pluto's demotion from planet to dwarf planet. Throughout his career, the Harvard- and Columbia-educated scientist has repackaged complex theories and universal mysteries into essays, presentations and books aimed at laypeople. He's hosted PBS's "Nova ScienceNow" series and produces a StarTalk Radio podcast and radio program. Tyson also helped resurrect Carl Sagan's "Cosmos" television series; he hosts a new version, which debuts in 2014.

Tyson has served as an adviser on the aerospace industry to President George W. Bush and on a later commission focused on space exploration policy. He was even voted People Magazine's "Sexiest Astrophysicist Alive" in 2000 [sources: Biography, Hayden Planetarium].