October 9, 2013 - NBC News
...
They followed up with observations using the Gemini North Telescope and
the NASA Infrared Telescope Facility telescopes on the summit of
Hawaii's Mauna Kea, and concluded that its infrared signature was more
consistent with a young planetary-mass object. The science team also
monitored the object for two years using the Canada-France-Hawaii
Telescope, to determine its direction of motion and its distance from
Earth. That's how they figured out it was 80 light-years away....