Hubble spies oddly conflicting behaviour of Pluto's moons

Wednesday, June 3, 2015, 7:25 PM - Astronomers using the Hubble Space Telescope watch the fascinating behaviour of Pluto's moons, a spacecraft preps to set sail and NASA celebrates 50 years of spacewalking!

NASA's New Horizons spacecraft is less than six weeks away from its historic encounter with Pluto, but it's not the only mission returning amazing science from that corner of our solar system.

Astronomers pointed the Hubble Space Telescope at this distant planetary system in order to better characterize the motions of the small moons, and pave the way for a smooth flyby for New Horizons. In the process, they made two amazing discoveries.

First, based on how Pluto's second largest moon, Nix, changes in brightness over time as it circles around Pluto and Charon, scientists believe that it has a very chaotic, tumbling rotation.

From this data, they believe that the video below gives a very good approximation of how this moon rotates.

According to Hubble, Hydra, the largest moon orbiting Pluto-Charon, apparently has the same chaotic tumble as it orbits.

Second, the Hubble observations show that the orbits of three of the moons - Styx, Nix and Hydra - are gravitationally linked together so that they form a resonance. That is, the gravitational influence of the moons on each other puts them into a very regular orbit, where periodically they always end up back in the same (or nearly the same) configuration. Pluto's second smallest moon, Kerberos, does not appear to be involved in this relationship.

As shown to the right, Styx orbits Pluto-Charon closer/faster than Nix, which orbits closer/faster than Hydra, and all three moons orbit counter-clockwise when viewed from above. However, specifically from the perspective of standing on the surface of Nix, Hydra - with an orbital period nearly twice as long as that of Styx - actually appears to orbit clockwise, making three orbits around Pluto-Charon for every two orbits that Styx makes.

A similar resonance relationship exists between Jupiter's moons - Io, Europa and Ganymede - so that, from the perspective of standing on Europa, Io makes two counterclockwise orbits for every clockwise orbit of Ganymede.

These amazing contrasting results - with Styx's chaotic tumble alongside the predictability of this gravitationally-linked trio, as well as new data about how the "binary planet" Pluto-Charon is warping the orbits of the smaller moons - is giving more insight into these types of systems and providing us with even more tantalizing hints of what we'll see when New Horizons makes its flyby in July.

"Hubble has provided a new view of Pluto and its moons revealing a cosmic dance with a chaotic rhythm," said John Grunsfeld, associate administrator of NASA’s Science Mission Directorate. "When the New Horizons spacecraft flies through the Pluto system in July we’ll get a chance to see what these moons look like up close and personal."

LightSail preps solar sails for Friday

After launching into orbit on May 20 and stressing out its ground controllers with more than a week of silence due to a computer glitch, the Planetary Society's LightSail-1 spacecraft is back in contact with the team and they are stepping up the mission timeline.

Although the deployment of LightSail's solar sails was originally scheduled for Day 28 of the mission - June 17, if everything went well - this has been moved up to Day 16 - Friday, June 5. In preparation for this, as of Wednesday morning, LightSail was ordered to deploy its solar panels, which not only provide power to the spacecraft, but also open the way for the sail to extend and unfurl.

With the difficulties of the computer glitch, the amazing good fortune of a sudden reboot due to a random encounter with a cosmic ray particle, and computer problems preventing a software update, the team is simply taking no more chances. This early deployment will give them the test results they're looking for, while reducing the chances of the universe making this mission any more "exciting" than it already has been.

Stay tuned for the results of solar sail deployment on Friday!

Celebrating 50 Years of Spacewalking

Fifty years ago, on June 3, 1965, Gemini astronaut Ed White became the first American to walk in space. 

We've come a long way since, and there are already plans for the future in the works.

Credit: NASA/Jason Roberts

NASA is celebrating this anniversary by asking how we "Suit Up".

• Head to the NASA website to see a gallery of different spacewalks that have happened over the years.
• Check out the details of suits from the past, present and future in NASA's collection of infographics.
• Watch NASA's documentary on 50 years of spacewalking, narrated by actor John Cryer
• Suit up, yourself, and show NASA how it's done on social media, using the hashtag #SuitUp

Sources: NASA | Hubble | The Planetary Society | NASA

WATCH BELOW: Astronaut Ed White takes his historic first spacewalk in this short video