NASA's Roman Space Telescope uncovers a brown dwarf and distant planet ahead of launch

Astronomers on Mauna Kea found the first space object on which NASA's Roman Space Telescope can test its imaging technology.

A new "massive planet" also was found, the W.M. Keck Observatory said in a Monday news release.

The discoveries are the first results from the OASIS program, which combines space-based measurements with the new Subaru Telescope's advanced imaging to "find hidden worlds," the National Astronomical Observatory of Japan said in a Dec. 4 news release.

"These results show what happens when we combine Maunakea's unmatched observing conditions with cutting-edge instrumentation," University of Texas at San Antonio professor and principal OASIS investigator Thayne Currie said in the Keck Observatory's release.

The first discovery was a brown dwarf, which scientists also call a "failed star," the Keck Observatory said. Brown dwarfs form like stars but never accumulate enough mass to become one. They are cooler in temperature and much fainter to the naked eye, but can be seen in longer, infrared wavelengths used in the Keck Observatory and Subaru Telescope.

The newly discovered brown dwarf, dubbed HIP 71618 B, was located 169 light-years away in the constellation Bootes, which can be found in the northern sky near the end of the Big Dipper's handle.

Data from both the observatory and telescope discovered the brown dwarf and, after a year of follow- up, revealed its orbit, the observatory said.

It's also the first object that is suitable to test NASA's Roman Space Telescope's technology, which are "tools future telescopes will depend on to image Earth-like planets that are billions of times fainter than their host stars," the observatory said. The telescope's strict criteria needs a bright host star, ideal separation and a companion that will be faint enough to challenge and confirm the telescope's performance.

"Providing a target that advances the community's preparation for this mission is directly relevant," Mona El Morsy, a University of Texas at San Antonio postdoctoral researcher and lead author of the brown dwarf study, said in the news release, adding that she is optimistic that the recent discoveries will "pave the way" for even more systems to be identified in the OASIS program.

The planet, called HIP 54515 b, was found orbiting a star 271 light-years away in the constellation Leo, the observatory said.

Its distance from its star was similar to Neptune's orbit around the sun, the observatory said, with the planet appearing "extraordinarily close to its host star as seen from Earth," comparable to the size of a football viewed more than 200 miles away.

The Subaru telescope's system "delivered the ultra- sharp images needed to reveal this faint, giant planet beside its bright star," while the observatory "played a critical role in interpreting it," the observatory said, noting it used more than a decade's worth of data to precisely calibrate the telescope.

The two discoveries "highlight the power of combining space-based precision measurements with the unparalleled imaging capabilities of Maunakea's observatories," the observatory said, adding that the OASIS program's early results demonstrate how the Subaru Telescope's system and Keck Observatory's infrared imaging and archival data "continue to uncover companions that would otherwise be invisible."

The OASIS project has uncovered more planets and brown dwarf companions through OASIS, which the observatory expects to announce in 2026. The program also plans to collect new images of both discoveries.