New Horizons on the Approach and a Contest to Name Pluto Surface Features

Is this what Pluto and Charon really look like? We’ll know more as the New Horizons mission gets closer to these distant worlds. Close flyby is set for July 14, 2015.

It’s exciting to think that we are now just a few weeks away from getting some of the first, clearest, and most detailed images of Pluto. The New Horizons mission will soon be close enough to start returning images similar in scope and detail to the first close-up images ever returned of distant worlds when the Voyagers swept past Jupiter, Saturn, Uranus, and Neptune in the late 1970s and 1980s.

Right now, Pluto’s still a large dot in the distance, and the spacecraft has been able to image its small moons Nyx and Hydra. That’s going to get better, of course. I talked with Alan Stern, PI of the New Horizons mission, and as you can imagine, he’s pretty psyched about it, even though the target is still not quite close enough to see good stuff. He’s Pluto Hugger #1, and has dedicated his career to this mission. So, it’s perfectly acceptable to find him excited and bouncing around about what the team will find. “In April, it’ll be a globe to us, and we’ll be about 70 million miles away from it,” he said, pointing out that he and the team have been speculating for years about what they’ll find.

At only a few pixels across in the best Hubble images, Pluto hasn’t been easily giving up its secrets. But, soon New Horizons will show us what it really looks like, and Alan and the team will find out more about the planet’s atmosphere as well as its surface.  “Pluto is a very reflective world—in much the same way fresh snow is,” he said. “We see from Hubble and other images that the surface has markings. Some are red, others are more neutral in color.  We know there’s hydrogen ice there, and methane and ethane, and carbon monoxide ice. How cratered is it? Is there any activity going on there?  What’s the geology of this planet? Those are all questions we’re going to have to wait to answer when New Horizons gets there in July.”

Alan has a fascinating blog on the New Horizons web page called PI’s Perspectives, and he’s been writing all along about the mission, what the team hopes to accomplish, and how the spacecraft works. You can’t get a better look at this last major planetary encounter than through Alan’s eyes, so check it out.

In case you are just starting to follow the New Horizons mission, here are a few facts about it. First, it’s been on the way to Pluto since launch on January 19, 2006. It’s traveling at a velocity (with respect to the Sun) of 14.58 kilometers per second (just over 9 miles per second). It will arrive for a Pluto flyby on July 14, 2015 11:49:57 UTC.

DSN 70-meter dish at Canberra, Australia. Image by Carolyn Collins Petersen. 

Right now, it takes just about 9 hours to send a round-trip message to the spacecraft and back. Mission controllers are communicating with New Horizons through the NASA Deep Space Network station Canberra, Australia, using the 70-meter antenna. You can track New Horizons communications at the Deep Space Network NOW page.

At Pluto, the spacecraft will continue its image- and data-taking routines, snapping images of the surface and moons, and measuring Pluto’s temperature, atmospheric composition, and other characteristics.

Right now (March, 2015) the spacecraft controllers are going through tuning routines for the instruments, and just did a course correction maneuver using an engine burn to fine-tune the spacecraft’s final trajectory toward the Pluto flyby. After it “threads the needle” past the Pluto system, New Horizons heads out further into the Kuiper Belt (a region of space stretching out beyond the orbit of Neptune and populated with many small worlds) and a possible encounter with two more worlds discovered by Hubble Space Telescope in 2014.

Keep an eye out on this little spacecraft that’s about to make some of the biggest discoveries in the outer solar system! The best way to do that is to check the New Horizons page every few days and see what the spacecraft team is doing and finding!

Want to get involved in some cool citizen science at Pluto? The Seti Institute, along with the New Horizons team, is inviting public input on surface feature names for Pluto. The name of the campaign is Our Pluto and the idea is to come up with surface feature names in advance to help the science team out. The campaign runs from now til April 7, so get on over there and contribute to the Pluto naming effort!  Join Alan, and me, and many others in a big “group hug” for Pluto!



Astronomers Spy Out Active Asteroids

Active asteroid P/2012 F5 captured by Keck II/DEIMOS in mid-2014. Top panel shows a wide-angle view of the main nucleus and smaller fragments embedded in a long dust trail. Bottom panel shows a close-up view with the trail numerically removed to enhance the visibility of the fragments.  CREDIT: M. DRAHUS, W. WANIAK (OAUJ) / W. M. KECK OBSERVATORY

In the “Department of Unusual Solar System Activities” today we have a close look at a type of asteroid that may spin so fast that it literally explodes itself as it ejects dust out to space. This comes to us courtesy of the W.M. Keck Observatory in Hawai’i, and a team of astronomers at the Jagellonian University of Krakow, Poland. To date, astronomers know of a handful of these busy objects and are seeking to understand why they do what they do.

The main asteroid belt of our solar system is likely a pretty orderly place, with asteroids moving along in their orbits without too many collisions, sort of like a well-run superhighway. But, sometimes things happen, even on a smoothly moving roadway. One car runs into another and that sets one or both of them spinning. Or, a truck has a blowout on its tire, and that sends it weaving all over the road.

In the case of the asteroid belt, which is home to the very fascinating Ceres dwarf planet (currently being studied by the Dawn spacecraft), we’re talking about “active asteroids” that are posing some interesting challenges to astronomers studying them. These are asteroids that eject steams of ice particles out as they orbit, most of the time in a steady jet. But, in 2010, astronomers found a more “explody” version of these objects. They eject material in shots, sort of like that tire blowout. The reasons they do this aren’t clear yet, but there are two ideas to explain them. One is that two objects—one moving very fast (say, at hypervelocity (which means really high velocity)) running into another. That causes one or both to catastrophically spew ice particles and dust to space in giant spurts.

The other idea is that an active asteroid experiences “rotational disruption”. That literally means it rotates so fast and wildly that it alters the shape of the asteroid, introducing cracks and crevices and fragmenting the body. As the active asteroid spins, it launches dust and ice chunks, which further unbalancing itself. Eventually, it can break apart.

The astronomers on the team using Keck focused in on a specific one that had caught their interest to see if they could capture a view of one of these tiny objects and figure out what makes it so unusual. The object they chose is called P/2012 F5, which had a big dust outburst in 2011. They wanted to measure its rotation rate (how fast it spins on its axes), and whether or not it was fragmented and broken apart. They found four large fragments in the object, which is rotating once every 3.2 hours. That’s fast enough to cause these impulsive explosions that result in dust and ice outbursts. For now, this object is still one big fragmented body. As it rotates, it is heated by the Sun on different sides and it’s possible that one day it will rotate itself apart, sending more ice and dust and fragments into space.

Interestingly, P/2012 F5 was first thought to be a comet due to its outbursts. Astronomers now know that it’s a fragmented asteroid, acting like a comet. Why it’s rotating and how it got fragmented—those are questions still to be answered.

Back in graduate school, we often talked about “asteroids acting like comets”, although they were quite rare. Now, what was once rare is an observable object, giving us another look at how amazing varied the places in our solar system can be.