Hubble Detects New Moon Orbiting Distant Dwarf Planet

NASA's Hubble Space Telescope, with the help of two other space telescopes, has detected a new moon orbiting a dwarf planet located at the outskirts of our solar system in the region known as Kuiper Belt.

The discovery, described in a paper published in The Astrophysical Journal Letters, was made 10 years after astronomers detected the distant dwarf planet catalogued as 2007 OR10.

"The discovery of satellites around all of the known large dwarf planets - except for Sedna - means that at the time these bodies formed billions of years ago, collisions must have been more frequent, and that's a constraint on the formation models," said Csaba Kiss of the Konkoly Observatory in Budapest, Hungary and lead author of the paper, in a press release. "If there were frequent collisions, then it was quite easy to form these satellites."

2007 OR10's moon was detected using the combined power of Hubble Space Telescope, Kepler Space Telescope and Herschel Space Observatory. The astronomers first thought of the possible existence of the moon when the observation from Kepler showed that the dwarf planet has a slow rotation period of 45 hours. Typically, objects in the Kuiper Belt have a rotation period under 24 hours. Slower rotation could mean that a planet is being affected by the gravitational tug of a moon.

Due to this, the researchers dug into the archival images of 2007 OR10 taken by Hubble's Wide Field Camera 3. Two separate observations by the Hubble, which were taken a year apart, showed the presence of the moon. The researchers noted that the moon is moving together with the dwarf planet. This means that the moon is gravitationally bound to 2007 OR10.

Using the observations in far-infrared light provided by the Herschel Space Observatory, the researchers were able to measure the diameter of 2007 OR10 and its moon. 2007 OR10 is about 950 miles across, while its moon measured around 150 to 250 miles in diameter. The dwarf planet follows an eccentric orbit and is considered to be the third largest dwarf planet in our solar system, following Pluto and Eris.