A bevy of Plutonian news has come down the pike today.

The Hubble Space Telescope issued a press release today confirming the discovery of two additional moons orbiting Pluto.

Anxiously awaited follow-up observations with NASA’s Hubble Space Telescope have confirmed the presence of two new moons around the distant planet Pluto. The moons were first discovered by Hubble in May 2005, but the science team probed even deeper into the Pluto system last week to look for additional satellites and to characterize the orbits of the moons.

Though the team had little doubt the moons are real, they were happy to see the moons show up very close to the locations predicted from the earlier Hubble observations. The initial discovery is being reported today in this week’s edition of the British science journal Nature.

The confirmation reinforces the emerging view that the Kuiper Belt, a swarm of icy bodies encircling the solar system beyond Neptune, may be more complex and dynamic than astronomers once thought. Pluto resides inside the Kuiper Belt and is about 3 billion miles from the Sun. Pluto was discovered in 1930.

The moons’ orbits are in the same plane as the orbit of the much larger satellite Charon (discovered in 1978). This likely means the moons were not captured, but instead were born, along with Charon, in what is commonly theorized to have been a titanic collision between two Pluto-sized objects over 4 billion years ago.

A team of astronomers, led by Hal Weaver of the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., and Alan Stern of the Southwest Research Institute in Boulder, Colo., made the new observations on Feb. 15, 2006, with Hubble’s Advanced Camera for Surveys (ACS).

The team used the sharp vision of the ACS to do a targeted search of the region around and inside the orbits of the twin moons. In addition to confirming the reality of the new moons, the observations also rule out the possibility of other satellites of roughly similar size orbiting Pluto inside the orbits of the two moons. The moons, provisionally designated S/2005 P 1 and S/2005 P 2, are approximately 40,000 and 30,000 miles away from Pluto, respectively.

Astronomers believe that the formation of the Pluto system is similar to that of our Earth and Moon. In both cases a comparable-sized body slammed into the parent planet. Simulations show that debris from the collision would go into an orbit around the planet and coalesce to form one or more satellites. Investigating how Pluto ended up with three moons while the Earth has only one should yield valuable insights into the processes by which satellite systems form around planets.

The team will use Hubble again on March 2 to study the new moons. They hope the follow-up observations will provide information on the moons’ color, as well as their size and shape, which could yield further clues about the formation and evolution of the Pluto system.

In the Hubble image, Pluto is in the center and Charon is just below it. P 1 is to the right and just below Charon. P 2 is to the right of Pluto and Charon.

Credit: NASA, ESA, H. Weaver (Johns Hopkins University/Applied Physics Laboratory), A. Stern (Southwest Research Institute) and the HST Pluto Companion Search Team

For images and additional information about this research on the Web, visit:

Johns Hopkins Applied Physics Laboratory
Southwest Research Institute

Additionally, it was reported today that Pluto may in fact have rings:

The two moons discovered around Pluto last year were likely formed from the same giant impact that created the planet’s much larger satellite, Charon, scientists say.

The idea suggests that other Kuiper Belt Objects might also harbor multiple satellites and raises the possibility that Pluto is encircled by rings fashioned from debris ejected from the surface of the tiny moons.

The two moons, called P1 and P2 for now, were discovered in May 2005 using the Hubble Space Telescope. Scientists now think the two moons are roughly 37 and 31 miles (60 and 50 km) in diameter. Charon has an estimated diameter of about 750 miles (1,200 km).

The moons’ tiny sizes raise the possibility that even more satellites might be discovered around Pluto in the future.

More on this intruiging possibility from Spaceref.com:

Image credit: SwRI, Painting by Don Davis

This artist’s rendering illustrates a giant impact scenario similar to one that likely resulted in the two, newly discovered moons of Pluto. A team led by Southwest Research Institute reports on this finding in a paper published Feb. 22, 2006, in Nature.

In a paper published today in Nature, a team of U.S. scientists led by Dr. S. Alan Stern of Southwest Research Institute (SwRI), concludes that two newly discovered small moons of Pluto were very likely born in the same giant impact that gave birth to Pluto’s much larger moon, Charon. The team also argues that other, large binary Kuiper Belt Objects (KBOs) may also frequently harbor small moons, and that the small moons orbiting Pluto may generate debris rings around Pluto.

“The evidence for the small satellites being born in the Charon-forming collision is strong; it is based around the facts that the small moons are in circular orbits in the same orbital plane as Charon, and that they are also in, or very near, orbital resonance with Charon,” says lead author Stern, executive director of the SwRI Space Science and Engineering Division.

“Tests of this scenario will come from refined orbital data, from measuring the rotational periods of these moons, and from determinations of their densities and surface compositions,” says co-author [Dr. Hal] Weaver.

Co-author Merline adds, “If Pluto’s small moons generate debris rings from impacts on their surfaces, as we predict, it would open up a whole new class of study because it would constitute the first ring system seen around a solid body rather than a gas giant planet.”

Dr. Stern is also the Principal Investigator for the New Horizons mission, which launched (more here) January 19th and is presently speeding toward a 2015 rendezvous with our distant, icy neighbor. Dr. Hal Weaver serves as a New Horizons project scientist.

Also, Emily Lakdawalla at The Planetary Society had recently asked readers to submit suggestions for the moons’ names, and there have been some interesting results thus far.

Great stuff!