WASHINGTON — Humanity’s journey to the stars is beginning with . . . a modest government grant.

The dreamers at DARPA, the Defense Advanced Research Projects Agency, last week announced an award of $500,000 to a former astronaut to launch an effort to — someday — send explorers to another star system.

It’s a huge job, impractical with existing technology. That’s why the 100 Year Starship Study project will start by building a community of space enthusiasts, engineers, technologists, futurists, scientists and dreamers to chip away at a panoply of technical, financial and social challenges — while seeking funds to keep the effort afloat.

“The first step is to get the seed money to grow into something more while also getting the public engaged,” said Mae Jemison, the former astronaut whom DARPA chose to head the effort. “It has to become something that has its own momentum.”

In 50 years of space exploration, humans have hardly made it out of the driveway of our home planet. NASA’s trips to the moon took three days each way. Mars, the next planet over, is nine months distant by robotic flier. At the speeds attained on those trips, the journey to the nearest neighboring star would take tens of thousands of years.

A starship, then, will need giant engines that draw more power than we know how to produce, said Les Johnson, a NASA scientist who has worked on designs for robotic probes to travel outside our solar system. “There’s no law of physics that says it won’t work,” he said. “Maybe if we get creative in our engineering we can do this.”

In its grant solicitation, DARPA wrote that it wants to “foster a rebirth of a sense of wonder” while encouraging research that will pay dividends here on Earth.

In Jemison, the agency tapped not only a space traveler — in 1992 she became the first woman of color to leave Earth, on the space shuttle — but a physician, engineer, entrepreneur and champion of science education.

Her vision: Generate excitement for a grand human adventure. Within a century, she wants the project to fund and foster the technologies needed to build a starship.

“It’s got to be a global aspiration,” she said.