NASA says its black-hole-hunting NuSTAR spacecraft has "bagged" its first 10 supermassive black holes, the first of hundreds expected in a 2-year mission.

The Nuclear Spectroscopic Telescope Array, sporting a mast the length of a school bus, is the first telescope capable of focusing the highest-energy X-ray light into detailed pictures, the agency's Jet Propulsion Laboratory in Pasadena, Calif., said Thursday.

Supermassive black holes surrounded by thick disks of gas lie at the hearts of distant galaxies between 0.3 billion and 11.4 billion light-years from Earth, project scientists said.

The first NuSTAR findings were unexpected but welcome, they said.

"We found the black holes serendipitously," David Alexander, a NuSTAR team member in the Department of Physics at Durham University in England, said. "We were looking at known targets and spotted the black holes in the background of the images."

Astronomers said they hope X-ray surveys by NuSTAR can help crack unsolved mysteries surrounding black holes, including how many of them populate the universe.

"We are getting closer to solving a mystery that began in 1962," Alexander said. "Back then, astronomers had noted a diffuse X-ray glow in the background of our sky but were unsure of its origin.

"Now, we know that distant supermassive black holes are sources of this light, but we need NuSTAR to help further detect and understand the black hole populations."