Pluto gets 14 new neighbours

By Heather Catchpole 15 September 2010
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By searching through old photos, astronomers have discovered 14 new space objects orbiting near Pluto.

PLUTO HAS GAINED 14 new neighbours, some of the faintest and smallest objects yet found in the region, say US researchers who discovered them.

These new icy bodies – known as trans-Neptunian objects or TNOs – range in size from 40 -100 km across, tiny compared to dwarf planet Pluto’s roughly 2300-km diameter. They are objects that orbit the Sun beyond the orbit of Neptune. Pluto, discovered in 1930, was the first recognised TNO.

Together with Pluto and other dwarf planets, TNOs form an icy ring around the Solar System and provide clues as to its origins.

Found in archived photos

“Trans-Neptunian objects interest us because they are building blocks
left over from the formation of the Solar System,” says astronomer César
Fuentes from the Northern Arizona University in Flagstaff, Arizona,
lead author of the research. “We think of TNOs as test particles,” he
told Australian Geographic.

“They are the leftovers of the
original proto-planetary disk, meaning they have managed to survive the
formation and evolution that the larger planets have experienced,” he says.

The astronomers trawled six years’ worth of Hubble Space Telescope photos, looking for the telltale streaks that show up as TNOs zoom across the sky in front of distant stars. The discovery will be published in an upcoming issue of The Astrophysical Journal.

The work to find the TNOs is notable because of the clarity of images taken from space and the use of archival information, says astronomer Michael Ashley from the University of New South Wales in Sydney, who was not involved in the research. “They use existing data so the discovery of these objects is a bonus.”

Aussie SkyMapper

He says Australia’s SkyMapper telescope in Siding Springs, NSW, will take “spectacularly large images” covering a greater portion of the sky. “This will provide a census of the largest Trans-Neptunian objects, possibly as large as Pluto,” he says.

Planetary scientist Charley Lineweaver, from the Australian National University in Canberra, led a study that helped define how TNOs are categorised as dwarf planets. He is currently working on adding another 50 dwarf planets to join Pluto and the others. “TNOs are interesting because they are primordial; they’re kind of like fossils,” he says.

Charlie says the US research is a different strategy for finding TNOs than has been used before. “I don’t think anyone has found such faint TNOs. Looking into deep space means they can find more distant and smaller objects.”

Dwarf planets accumulate in outer Solar System