Blogs / Bad Astronomy

Pity poor Pluto. The debate over its planethood has caused much consternation over the years. Part of the problem is that it’s so dinky and so far away! If it were closer, or bigger, we almost certainly wouldn’t be having this debate.

But whether or not you think Pluto should be part of the gang or not, one thing is certain: it’s a world unto itself. And to bring this point literally home, the Hubble Space Telescope has revealed the changing face of this tiny iceball:

These images, just released today (but taken in 2002), represent the most detailed surface map of Pluto ever taken. Even in Hubble’s Advanced Camera for Surveys Pluto is only a few pixels across, but it’s possible using sophisticated image processing techniques to tease out the detail seen.

Here’s a nifty animation of Pluto rotating using these maps:

Very cool. But these maps are more than just eye candy. They show significant changes on Pluto’s surface since the last maps were made using Hubble 16 years ago. Pluto’s north pole is brighter and the south pole darker, implying that material has migrated from one pole to the other, or at least that the poles are changing in different ways. Pluto orbits the Sun "on its side", dramatically more tilted than Earth’s mere 23.5°. Right now, the north pole of the world is facing the Sun, meaning it’s summer on Pluto’s northern hemisphere (as it’ll remain for a long time, given Pluto’s 248 Earth-year long year).

Not only that, these images show that Pluto has reddened quite a bit in the past few years. This is one reason it took so long to release the images; Marc Buie, the astronomer who took them, saw some things in the data that were difficult to understand, and wanted to make sure they were correct. These images are composites of pictures taken using a blue and a green filter. During the time these observations were made, in 2000 – 2002, Pluto got much darker in blue, which was unexpected. Pluto’s moon, Charon, did not get any bluer, indicating that the cause was something intrinsic to Pluto and not that something weird happened with Hubble.

So why is Pluto redder now? That’s not clear. In general, ultraviolet light from the Sun interacts with the chemicals on Pluto, creating reddish organic molecules; this is seen on lots of distant, icy objects in the Kuiper Belt (the region past Neptune where Pluto orbits). Incredibly, even at the numbing distance of over 4 billion kilometers (3 billion miles) from the Sun, Pluto is still strongly affected by it. But this is happening while overall the northern hemisphere got brighter and the southern darker. You’d expect Pluto to get darker if it gets redder, so clearly there’s more going on here than meets the eye.

These maps will prove crucial in planning the imaging run of the New Horizons probe, which will scream past Pluto in 2015. Having even a crude map in advance of the encounter will help scientists plan their limited time more carefully.

Plus, these Hubble images may very well be the best view we’ll get until New Horizons gets to Pluto, for that matter. And whether you think Pluto is the littlest planet or one of the biggest of the Kuiper Belt Objects, it’s a fascinating place worthy of a lot more study. And in just a little more than five years we’ll see fantastic images of it, too. I can’t wait!

Video courtesy Emily Lakdawalla (and my thanks to her for a helpful conversation). Image and video credit: NASA, ESA, and M. Buie (SwRI)

One of the closest and most spectacular galaxies in the sky is M51, the Whirlpool. A grand design face-on spiral with a small, irregular companion, it’s so bright and big that it’s a favorite target for amateurs. So you just know when you point Hubble at it, what you get is nothing short of jaw-dropping heart-aching beauty.

Voila:

[Click to galactify.]

This image, using the Hubble Advanced Camera for Surveys, was originally released in 2005, but was recently reprocessed by the phenomenal astrophotographer Robert Gendler. And yeah, you absolutely want to click that link to see the work Robert has done. He’s incredible.

I could go on and on about the galaxy, the glorious spiral arms, the red glow of nebular star birth factories, the odd companion that apparently has drawn out that long tidal tail of stars from the spiral, and so on… but you’ve read that stuff here before.

Instead, while looking this image up, I found the behind-the-scenes story on how they observed it that I think will interest you, my BABloggees. Extra cool is the page showing the galaxy observations in different colors, and you can see just what a big spiral looks like when you use different filters:

You can see the ACS field of view, and the final version on the left. The different observations are listed (each frame is clickable to embiggen on that page, which lets you explore the galaxy on your own). The filters are labeled on the top of each image: B (blue), V (visual, or really yellow), I (near-infrared), and Hα + [NII], the reddish light given off by hot hydrogen clouds laced with nitrogen. That last bit is where stars are being born, and traces the spiral arms very well. The I-band shows very warm dust as well as stars, so it looks smoother since all that stuff is rather smoothly distributed in the galaxy. The B-band has hot stars in it, so again shows where stars are being born; blue stars don’t live very long, and can barely escape their gas cloud nurseries before blowing up as supernovae.

When you put these all together you get the majesty of a spiral galaxy, a city of stars much like our own Milky Way. I’ve seen M51 myself with binoculars and through countless telescopes at star parties, and while it doesn’t look as glorious as it does here — of course — just knowing what’s going on in the galaxy and what it really does look like through the big guns is enough to thrill. It may look blurry and fuzzy through a small telescope, but our brains are big enough to encompass all those light years, and to understand what it is we’re seeing.

Image Credit: NASA, Hubble Heritage Team, (STScI/AURA), ESA, S. Beckwith (STScI). Additional Processing: Robert Gendler

I have a tale of death, near death, and undeath to weave for you, but first, gaze upon the jewel-like beauty of the glittering denizens of M30:

This image was taken by the Advanced Camera for Surveys on board the Hubble Space Telescope. I had to cut it and compress it drastically to get it to fit on the blog, so you very much want to click on it to embiggen it massively and see it in its fully resolved glory.

The image is of the insanely beautiful globular cluster M30, an ancient city of a few hundred thousand stars located 28,000 light years away in the constellation of Capricornus. The cluster is ancient, about 13 billion years old, making it as old or even older than the Milky Way itself. The core of the cluster is unusually dense as such things go, which is why it was studied. Where better to find vampires and thrillseekers?

Like people, stars are born, age, and die. Stars born with more mass tend to die off more quickly, consuming their fuel at far higher rates than their lower-mass brethren. These stars tend to be blue, so in an old cluster like M30 you’d expect to see no blue stars at all; they should all be long gone. And yet, there are quite a few — astronomers call them blue stragglers. Where did they come from?

One theory, which has been borne out by observations, is that blue stragglers are in tight binary systems, with a dead star in such close proximity to a normal star that it can siphon off the normal star’s gas, using it to rejuvenate itself. This would make them vampires, of course, sucking the life force of other stars in an attempt to stay young.

But another idea was that dead stars might also physically collide with other stars and merge, forming a single star that would burn blue and bright. In an environment like that near our own Sun this kind of collision can almost literally never happen; even considering the entire Milky Way Galaxy over its entire lifetime a head on collision has probably never happened out here in the stellar suburbs.

But that cluster M30 is pretty densely populated with stars, and collisions are far more likely. What observations like this one of the cluster (and also of an ancient cluster called NGC 188) have shown is that the blue stragglers appear to have two different sub-groups; one that appears to have come from the vampire stars, and another from stars that have collided: thrill-seekers, stars that have physically slammed into each other and merged, their combined mass separating them from the other blue straggler group.

Blue stragglers have been known since the 1950s, and the idea that they were pulling gas off nearby stars was proposed to explain them, too, but it’s only with our modern instrumentation that we can not only show that this is true, but that a second, far-fetched-sounding scenario of collisions also contributes.

I find it wonderful and extremely uplifting that an image as spectacular and gorgeous as the one above — it became my desktop wallpaper as soon as I saw it! — not only satisfies our desire for beauty and art, but can also be tapped to deliver incredible science that boosts our awe of what Nature can do. I love that we can understand such things, but you know what I love even more? The idea that we have only begun to understand the Universe.

If you thought the Lagoon yesterday was pretty, then reset your awe-meter. Check. This. Out.

D’ya like that? Huh? Do ya? Had enough? No? Then check THIS out!

Jeebus. Click either to brobdingnangate. In fact, you can get massively huge versions here and here. We’re talking 30 and 40 Mb each, so be ye fairly warned, says I.

Those magnificent images are of the galaxies NGC 4402 and NGC 4522, respectively, as seen by the Hubble Space Telescope’s Advanced Camera for Surveys (from before the recent repair mission). They’re both spiral galaxies in the Virgo Cluster, the nearest large collection of galaxies to us, roughly 60 million light years from Earth.

If they look funny to you, then good! The Virgo Cluster is massive, and has a lot of gravity. The galaxies bound to it are moving like bees surrounding a hive, each in its own orbit going every which way. These galaxies are screaming through the cluster at speeds of 10 million kilometers per hour, a truly terrifying velocity.

There is an ethereal gas distributed between the galaxies called the intercluster medium. It’s incredibly thin, but over the size of a galaxy — especially when said galaxy is barreling through it at such tremendous speed — the gas can exert significant pressure, called ram pressure. The pressure is actually blowing the galaxies’ internal gas clouds out into the cluster itself, making them look a little bit like pickup trucks driving down a highway with dirt copiously pouring out the beds^*. This is especially obvious in NGC 4522 (the lower one), where you can see bright blue splotches, which are regions of intense star formation, along with dark lanes of dust actually above the galactic plane.

In NGC 4022, you can see how the ram pressure is roiling up the dust in the galaxy, and also blowing it back, though apparently not as briskly as in the other galaxy.

These pictures are incredible. Poke around them; you can see amazing detail in the galaxies themselves, as well as hundreds, maybe thousands of background galaxies.

It’s been a while since we’ve seen deep, glorious pictures of spiral galaxies from Hubble. Now that ACS is working again, and it’s being joined by the equally powerful Wide Field Camera 3, we’ll be seeing lots more of these. Get used to it.

Image credits: NASA and ESA.