In 2015, NASA’s New Horizons spacecraft will zip past Pluto, giving us our first close-up view of this tiny world.

The team behind the space probe have a nice idea to help raise awareness of it: make a new US Post Office stamp commemorating it. My friend Dan Durda, both an accomplished astronomer and artist, created this lovely design of the stamp:

[Click to enhadesenate. Note: the word "Forever" means the stamp is always good for first class postage, and is crossed out here to prevent forgery.]

It shows the spacecraft going by Pluto and its (relatively) freakishly large moon Charon. I like how he didn’t go for photorealism, but instead used an oil paint-like feel for it. The stamp is meant as a followup — I might even say send-up — of a US stamp issued in 1990 about Pluto that has the label "Not Yet Explored".

I like this stamp! I’d love to see it made official, too. Alan Stern, the head guy for the mission, created a petition to help that along. It takes more than just a nice stamp design to get the PO’s notice; it has to have public support as well. I signed the petition, and if you want to, please do.

I’ll note that I expect this to raise the specter of whether Pluto is a planet or not. I have some thoughts on that, and I’ll be posting again soon on that topic.

This is pretty nifty: astronomers have discovered a fourth moon orbiting Pluto!

The tiny chunk of ice was found in Hubble images taken just a few weeks ago, and was clearly seen among the three previously known satellites:

It doesn’t have a name yet — it’s designated S/2011 P1 (or just P4 informally) — and it’s only about 13 – 34 km (8 to 21 miles) across. The size is estimated by measuring its brightness and assuming it’s icy like Pluto itself — a more reflective (white or icy) object would appear brighter than a darker object if they are the same size. Since its actual reflectivity isn’t known, the size has a wide range. But it’s still pretty dinky. For comparison, Pluto itself is 2300 km across, and its biggest moon Charon is well over 1000 km in size. I’ll note our own Moon is 3470 km across, so even Pluto is pretty small.

The thing is, in that single image above you can’t be sure if the object is a moon or a coincidentally placed background star. The solution: take a second image! That was done, clinching the moon’s identity:

See how it’s moved? Mind you, in the week or so between these two images Pluto moved substantially compared to background stars, and the moon moved along with it around the Sun at the same time it’s going around Pluto. You can see the motion of the other moons as well.

In the image, the diagonal lines are an optical effect inside the telescope itself. Pluto is very bright, so the astronomers used some processing techniques to make it appear much fainter, taking multiple images and subtracting one from the other to remove the glare of Pluto (it doesn’t work perfectly, which is why there is a black strip across the image; that blocks unwanted noisy light). I did this myself on many images when I worked on Hubble. It’s amazing how well it works, as you can see in the image above.

Mind you, Pluto was 5 billion km (3 billion miles) from Earth when this image was taken! But we’ll soon get much better pictures: the New Horizons probe will fly past the tiny world in 2015, snapping away as it does. We’ll probably learn more about Pluto in a few hours than we have since its discovery in 1930.

I wonder what they’ll name this iceball? The two moons Nix and Hydra (discovered in 2005) were named after Roman mythological characters associated with night time and Pluto. Cerberus seems like an obvious choice, but there’s already an asteroid with that name. Maybe they can change the spelling a bit to Kerberus to get around that. There’s already an asteroid named Persephone, too, if you’re curious. We’re running out of good names!

Well, whatever it’ll be called, it’s there, and we’ll see it up close in personal in just a few more years.

Credit: NASA, ESA, and M. Showalter (SETI institute)

In July 2015, the New Horizons probe will fly past Pluto, snapping pictures and taking data of this icy world. Whether you think Pluto is a planet or not^* it’s still a fascinating object and I can’t wait to see what New Horizons sends back.

But what happens after that? The space probe will still be traveling into deep space at high speed… but space out there isn’t empty. Beyond Pluto lie the solar system’s coldest denizens, the Kuiper Belt Objects. These are lumps of ice, frozen chunks that may take millennia to circle the Sun once. We’ve identified over a thousand of these KBOs, and there are tens of thousands more waiting to be discovered. Scientists with the New Horizons mission are hoping to find one near enough to the probe’s path to plan a flyby, so we can finally see one of these things up close.

And that’s where you come in!

A new website, Ice Hunters, has been put together to help you find potential KBOs for New Horizons to visit. It’s part of the Zooniverse; a citizen science project that gets people involved in real astronomy. In this case, you can examine images from the giant Magellan and Subaru telescopes to look for targets. It’s actually not terribly hard; here’s one image I looked at:

Basically, KBOs move over time, so two images are taken some time apart. One is digitally subtracted from the other, so stars tend to go away (though they don’t erase perfectly, leaving those ugly residuals). Any whitish blobs left are things that have changed between the two images: variable stars, asteroids, cosmic rays, and, hopefully, KBOs. When you find something you simply tag it by clicking it. A circle is placed around it, and the location is logged. You can see the object I found in the image above.

Humans are pretty good at this, while computers are easily confused by the messy residuals. But just to make sure every click is saved and compared to the work of other people. The more an object is clicked, the more likely it is to be something real and worth following up. The website explains how all this works.

That’s all there is to it! You have to register to do this (unless you’re already a Zooniverse member); it’s free and easy. And who knows? You may literally be the person who finds an icy world that will get a visit from New Horizons!

New Horizons image credit: Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute (JHUAPL/SwRI)

^*My opinion: defining the word "planet" is a bad bet if not impossible. If you want the longer story, check out this article I wrote for Discover Magazine.

Mike Brown is an astronomer, and in my opinion is mainly responsible for kick-starting the demotion of Pluto as a planet — he and his team found Eris, an object in the outer solar system that was apparently bigger than Pluto. It was this discovery which set in motion the events that led to the foofooraw about Pluto, and the vote that turned it (and Eris and many others) into "dwarf planets".

Mike continues to observe Eris and other dwarf planets (as well as search for new ones). These objects are small and far away — did you know our own Moon is substantially larger than Pluto? — and therefore hard to analyze. Even with huge telescopes, these objects are hardly more than dots.

However, a fortuitous event landed in the laps of astronomers recently: Eris passed directly in front of a faint star. To us on the ground, it appeared as if the star winked out as the dwarf planet passed in front of it. By carefully timing the duration of this mini-eclipse, the size of Eris could be estimated.

And, to everyone’s shock, Eris looks to be roughly the same size as Pluto. Mike describes all this on his blog.

What does this mean for Pluto? (more…)

Speaking of Pluto, one of my favorite web comics, Big Fat Whale, has a pretty funny one up about tabloid science.

Poor Pluto. First Mike Brown demotes it, then it’s caught in a custody battle.

I’m a big fan of satire, and BFW is a great mirror on society. I suppose some of it is NSFW, but then, that’s one of the reasons I work from home. Everything is SFW for me!

Astronomer Mike Brown is a friend of mine. He’s a pretty nice guy, and while he’s not exactly sad that he was instrumental in getting Pluto demoted from its planethood status — his Twitter handle is @PlutoKiller, after all — I don’t think he deserves all the slings and arrows he’s received.

And he certainly doesn’t deserve an elbow to the nose, as LA Laker Ron Artest recently said. I can understand Mr. Artest’s lament at some level, but physical punishment will only redouble Mike’s efforts, and who knows what will happen then! We might lose Neptune.

So if I had to think of suitable punishments, they’d be

1) a pie to the face,

2) a Benny Hill-style rapid-repeat slap on the top of the head,

3) a dressing down by Goofy, or just possibly

4) more telescope time.

I don’t think he’d disagree with any of these, with the exception of getting a pie to the face before more time on a telescope. Whipped cream is hard to get off a 10-meter mirror.

Tip o’ the nose guard to Jerome Clemente. Image credit: Ball Don’t Lie.

When Pluto was discovered 80 years ago, it happened to be moving through Gemini, a part of the sky that had a lot of stars. Clyde Tombaugh did an amazing job finding it, since it was almost lost among those stars.

I wonder if he could’ve found it had he been looking earlier this year? "Amateur" astronomer Anthony Ayiomamitis sent me this image he took of Pluto as was in Sagittarius, the most densely-packed area of the sky!

[Click to undwarfplanetate.]

Hard to spot, isn’t it? Pluto is unresolved in the picture, so it looks like just another star. And there are a lot of stars here; this region of sky is actually a cluster called Messier 24 (or just M24, and it’s pronounced "MEZ-ee-ay", since Charles Messier was French); the two dark splotches are thick dust clouds called Barnard 92 and 93. Finding Pluto in this ain’t easy.
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