Astronomers using the Hubble Space Telescope have found a tiny, dark moon circling the dwarf planet Makemake, a Pluto sibling in the solar system's distant Kuiper Belt.
It is the first satellite to be discovered circling Makemake, an 870-mile wide dwarf planet discovered in 2005.
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Makemake, which is named for a creation deity of the Rapa Nui people of Easter Island, is the second brightest object in the Kuiper Belt after Pluto.
The dwarf planet's newly found moon, spotted in an April Hubble Wide Field Camera 3 image, is more than 1,300 fainter than Makemake, NASA said in a press release issued Tuesday, the same day the discovery was announced in a Minor Planet Electronic Circular.
The moon, nicknamed MK 2, is estimated to be about 100 miles in diameter. It is located about 13,000 miles from Makemake and appears to be orbiting edge-on, relative to Earth's perspective.
"That means that often when you look at the system you are going to miss the moon because it gets lost in the bright glare of Makemake," astronomer Alex Parker, with the Southwest Research Institute in Boulder, Colo., said in a statement.
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Astronomers will now try to learn more about the moon's orbit so they can calculate a mass for the system and learn more about how it formed.
"The discovery ... has given us an opportunity to study Makemake in far greater detail than we ever would have been able to without the companion," Parker said.
Preliminary estimates indicate that if the moon is in a circular orbit, it completes a circuit around Makemake in 12 days or longer.