NASA's newest eye on the sky, the Nancy Grace Roman Space Telescope, has begun its journey to unravel the secrets of dark matter, dark energy and Earthlike planets — months ahead of schedule.

The 9-ton telescope rode to space today aboard a SpaceX Falcon Heavy rocket that was launched from NASA's Kennedy Space Center in Florida at 7:26 a.m. ET (11:26 UTC). The ascent went off without a hitch, setting up the telescope for a three-month cruise to a gravitational balance point known as Earth-sun L2, a million miles beyond our planet. The Falcon Heavy's two side boosters flew themselves back to landings on the Florida coast, near the launch site, while the center core booster splashed into the sea after stage separation.

NASA had originally scheduled liftoff for 2027, but the $4.3 billion mission came in ahead of schedule and under budget.

Here are five key facts about the Roman Space Telescope and its mission...