Astronomers reviwed the data archives of NASA’s Hubble Space Telescope have added 14 new Trans-neptunian object (TNOs). The newfound TNOs range from 25 to 60 miles (40-100 km) across. This would make them around the sizes of the 8th to tenth largest moons of Jupiter and larger than Phobos (moon of Mars).
This initial study examined only one-third of a square degree of the sky, meaning that there is much more area to survey. Hundreds of additional TNOs may lurk in the Hubble archives at higher ecliptic latitudes. Fuentes and his colleagues intend to continue their search.
As TNOs slowly orbit the sun, they move against the starry background, appearing as streaks of light in time exposure photographs. The team developed software to analyze hundreds of Hubble images hunting for such streaks. After promising candidates were flagged, the images were visually examined to confirm or refute each discovery.
Most TNOs are located near the ecliptic — a line in the sky marking the plane of the solar system (since the solar system formed from a disk of material). Therefore, the team searched within 5 degrees of the ecliptic to increase their chance of success.
They found 14 objects, including one binary (two TNOs orbiting each other like a miniature Pluto-Charon system). All were very faint, with most measuring magnitude 25-27 (more than 100 million times fainter than objects visible to the unaided eye).
By measuring their motion across the sky, astronomers calculated an orbit and distance for each object. Combining the distance and brightness (plus an assumed albedo or reflectivity), they then estimated the size.