Astronomers discover fifth moon orbiting solar system’s smallest planet

Astronomers discover fifth moon orbiting solar system’s smallest planet


A new satellite orbiting Pluto has been spotted using NASA’s Hubble Space Telescope, a discovery that could bring the solar system’s smallest planet back into the spotlight for the world of astronomy.

Astronomers estimate the moon to be 6-15 miles across with a 58,000-mile circular orbit around the dwarf planet.  The new moon joins Pluto’s other satellite objects: P4, Nix, Hydra, and Charon (the largest of the five, discovered in 1978). The moon was detected in nine separate sets of images taken by Hubble’s Wide Field Camera 3 on June 26, 27 and 29, and July 7 and 9, NASA says.

Astronomers say they are fascinated that a small planet in the Kuiper belt can have so many satellites. The Kuiper belt is a region of orbiting objects similar to that of our solar system’s asteroid belt, but in the far reaches of our solar system. Researchers think that Pluto’s number of satellites may be due to a collusion between Pluto and another large Kuiper belt object billions of years ago.

The team described the newly discovered moon as a stunning find that could provide astronomers with additional incentive to further examine the planet and its interactions with neighboring moons. Astronomers say further research regarding Pluto’s various moons may help scientists better understand the origins of the Solar System and how planets came to be.

“The moons form a series of neatly nested orbits, a bit like Russian dolls,” said team lead Mark Showalter of the SETI Institute.

The discovery also lends insight into the understanding of Pluto and what can be expected from NASA’s New Horizons spacecraft set for Pluto in 2015. New hazards need to be discovered in order to protect the spacecraft on its mission as it flies past Pluto at 30,000 miles per hour. The discovery of another satellite orbiting Pluto is critical when considering New Horizons could be destroyed by BB-pellet-size debris.

“The discovery of so many small moons indirectly tells us that there must be lots of small particles lurking unseen in the Pluto system,” said Harold Weaver of the Johns Hopkins University Applied Physics Laboratory.

Astronomers are planning to use Hubble’s intended successor, NASA’s James Webb Space Telescope, for follow-up infrared observations. This will give researchers the ability to measure the surface chemistry of Pluto and its surrounding satellites along with other Kuiper belt objects.

“The inventory of the Pluto system we’re taking now with Hubble will help the New Horizons team design a safer trajectory for the spacecraft,” added Alan Stern of the Southwest Research Institute, the mission’s principal investigator.

The finding could keep the Hubble Space Telescope in operation beyond its expected shutdown. Hubble is expected to remain operational through the end of the decade when it will be replaced by the  James Webb Space Telescope, slated for launch in 2018. The James Webb Telescope will have a larger mirror and will study Pluto after the New Horizons mission.

“Finding this moon was exciting and shows us Pluto is an intriguing and complicated place,” said NASA scientists.

As for the name of the newly discovered moon, it remains unclear whether the U.S. space agency will seek suggestions. Pluto was the god of the underworld in Roman mythology. Charon, the largest of Pluto’s moons, is named after the mythical ferryman who carried the souls of the newly deceased across the River Styx, which separated the world of the living from that of the dead, according to NASA.

The finding comes over a year after Pluto was a full-fledged planet. Since then, astronomers have demoted it to a dwarf planet, a decision that was met with controversy within the scientific community.

In January, Universe Today’s Fraser Cain explained why Pluto is not longer considered full-fledged planet: “Instead of being the only planet in its region, like the rest of the Solar System, Pluto and its moons are now known to be just a large example of a collection of objects called the Kuiper Belt.”

Mr. Cain says that Pluto fails to meet the third requirement for full-fledged planet status, which is why researchers demoted it to a dwarf star. It remains to be seen if the discovery of an additional moon will force astronomers to reconsider Pluto’s place within the Solar System.

The finding was the result of an international effort involving NASA and the European Space Agency. Their research is leading to a more refined understanding of celestial bodies in the far reaches of our solar system.