About 700 light years away sits the expanding death cry of a star: the Helix Nebula, a four-light-year wide gas cloud blasted out when a star that was once like the Sun gave up its life.

A new image of it in colors just outside what the human eye can see shows just how much it does look like a screaming star:

[Click to ennebulenate, or download the huge 6600 x 600 pixel 35 Mb version.]

This image is in the near-infrared, taken using the European Southern Observatory’s Visible and Infrared Survey Telescope for Astronomy (VISTA), a 4.1 meter telescope in Chile. Equipped with a whopping 67 megapixel camera it can take pictures of large areas of the sky. The Helix nebula fits that bill: it’s close enough to us that it’s nearly the size of the full Moon in the sky.

This image is pretty nifty. It accentuates cooler gas than what we see in visible light. What’s colored red in the picture is actually infrared light coming from molecular hydrogen, and shows the sharp ring-like edge of the nebula. What you’re seeing here is not so much a ring as it is the walls of a barrel-like structure, and we happen to be seeing it nearly right down the tube (see Related posts below for all the info you could want on this amazing object).

It also accentuates the long, long streamers pointing directly away from the center. Those are comet-like tails coming from denser clumps of material boiling away as the fierce ultraviolet light of the central star floods out, their material flowing radially outward. This is seen in other nebulae as well.

And while it’s beautiful and scientifically very useful (I would’ve killed for data this nice when I was researching these nebulae in grad school), it’s also something of an existential reminder: someday, our own Sun will look a bit like this. Probably not quite this bright and well-defined; our local star doesn’t quite have the power needed to light up its surroundings this way. But for all intent and purpose, you’re seeing a snapshot of our solar system in seven or eight billion years.

Just in case you needed a little perspective this morning.

Image credit: ESO/VISTA/J. Emerson. Acknowledgment: Cambridge Astronomical Survey Unit

I am fascinated by junk floating around stars. And no, not paparazzi, har har. I mean circumstellar material, literally gas and dust orbiting other stars. We see it around stars that are dying, we see it around stars being born, and we see it even after stars are well into their youth.

One such young’un is the bright and shiny HR4796, a star 240 light years away, with about twice the mass of the Sun. It’s known to be less than 10 million years old — compare that to the Sun’s age of 4.56 billion years; we’re 450 times older! — and has also been known for some time to have material around it in the shape of a ring. New observations by Japan’s huge 8.2 meter Subaru telescope have provided some of the sharpest views of this ring ever taken, and revealed some surprises.

Isn’t that lovely? [Click to enannulusenate.]

This picture is in the infrared, well outside what the human eye can see. The star itself is so bright it’s saturated, overexposed. That part of the picture is blocked out to make it easier to see details around it, but the star’s position is marked with a dot. The tendril-like structures radiating outward are not real, but are artifacts of the image processing techniques. You can ignore them.

The important thing is the ring itself, which is easy to spot. It’s almost certainly a circle, but we’re seeing it at an angle (about 13° from edge-on) so it looks like an ellipse. It’s huge; 22 billion km (14 billion miles) across, more than twice as wide as our entire solar system.

Again, the ring has been known for some time; for example it was seen in Hubble observations back in 2009 [NOTE: as astronomer (and my friend) Glenn Scheider points out in the comments below, HR 4706's ring was seen long before 2009. I wasn't clear when I wrote the previous statement; I was only alluding to one particular earlier observation, but it wound up sounding like it was the earliest such observation. My apologies for any confusion.]. But there is some new stuff here. For one, if you look along the long axis of the ring, you can see it looks fuzzy. That’s real! The ring is made of dust grains of various sizes, probably the result of bigger clumps colliding with each other and grinding themselves up into ever-smaller pieces (the authors of this reasearch (PDF) call this a "collisional cascade", my new favorite phrase for 2012). These grains of dust orbit the star, and the smaller ones get blown away from the star due to the pressure of its fierce light. Bigger grains are less affected, so they tend to stay in place.

So the main ring is made of bigger grains, while the smaller ones are blown back, forming a larger, extended ring. That fuzzier outer ring is fainter and harder to see, but we see it more easily along the long axis because of geometric effects (similar to why soap bubbles and giant shells of cosmic gas look like circles in space). So even though we only see a part of this outer ring, the fact that we only see it in those two spots is what makes it clear we’re seeing a ring at all! Funny how that works.

(more…)

For some reason, a lot of gorgeous pictures are being released after I post my Top 24 Deep Space Pictures of 2011 gallery. Figures. Since I already had a few images from NASA’s WISE observatory in the gallery anyway I guess can’t complain too much, especially when they release one as pretty as this!

[Click to infraredenate.]

This is Barnard 3, a dusty, gassy region of the galaxy about a thousand light years away where young stars are lighting up their neighborhood. WISE observes the skies in the far infrared, well past what our eye can detect, so this false-color picture mostly picks out the dust warmed by nearby stars. What you see as green and yellow-green is actually from long, complex molecules similar to soot, called polycyclic aromatic hydrocarbons or PAHs. Red shows cooler material.

So what’s going on here? Right in the center of the red splotch is a star which is brighter and hotter than our Sun, and is flooding the surrounding material with ultraviolet light and a fast wind of subatomic particles (like the Sun’s solar wind, but a whole lot stronger and with a much, much farther reach). This has carved out a gigantic cavity in that stuff, creating a bubble about 25 light years in diameter — that’s huge: 250,000,000,000,000 kilometers across, more than 10,000 times the size of our solar system!

(more…)

Astronomers may have, for the first time, directly imaged a planet still in the process of formation, gathering material from a debris disk surrounding its parent star.

First: Holy Haleakala!

Second: note the use of the word "may". It looks to me like it’s real, though.

Third: Oh, you want to see the picture? Well, let me do the honors:

The alleged planet, called LkCa 15b, is the blue spot in the image. The red shows material which is most likely accumulating onto the planet itself, building up its mass. The central star isn’t seen in this image because its light has been blocked out so the fainter material near it can be seen. The star’s position is marked by the star icon.

The image is in the infrared, taken using the monster Keck telescope in Hawaii. What’s shown in red is light at a wavelength of 3.7 microns (roughly five times what the human eye can see) and blue is from 2.1 microns, about three times what we can see. Warm material around the star is best seen at these wavelengths. If this is a planet, it’s at a temperature of about 500 – 1000 K (440° – 1340° F), and has a mass roughly six times that of Jupiter, or about 2000 times the Earth’s mass.

So is it a planet? (more…)

I know I just posted a global color map of Saturn’s moon Titan, but sometimes it’s cool just to take a step back and look at a picture that gives a little context… and it doesn’t hurt that it’s a moody grayscale shot, too:

[Click to encronosenate.]

This shot of Titan was taken by the Cassini spacecraft back in August, and shows the moon superposed on Saturn’s rings, seen here almost — but not quite — edge-on.

The fact that you can see surface detail on Titan is a dead giveaway this shot was taken in the infrared: optical light, the kind we see, can’t penetrate the thick, hazy, nitrogen/methane atmosphere blanketing this moon. Infrared light gets through, though, so surface features can be seen. In fact, this image was taken using a filter that lets through light at 938 nanometers (the reddest light the human eye can see is about 750 nm). Methane is pretty good at absorbing light at a bunch of different wavelengths, but at 938 nm it’s transparent, so this is a particularly good place in the spectrum to look at Titan — astronomers call it the "methane window". Not only that, but this image also employed a polarizing filter, which blocks a lot of light from the atmospheric haze, making the surface easier to see (it also makes rainbows appear and disappear, too).

Not that the atmosphere is completely invisible in this picture: look around the moon’s edge and you can just see some of the upper atmospheric layers, and at the top you can easily spot the north polar hood, which may have water ice crystals in it.

And that dark region on Titan’s surface? It may have once been the bed of a methane sea, but now it’s a dry, vast area of wind-blown dunes, hydrocarbon grains collected by the Titanian winds. It’s called Shangri-La, and that makes me smile. I’m not sure anything at -180°C could be called a human paradise, but for astronomers, it’s certainly a scientific one.

We’ve sent space probes to every planet in our solar system (and if you’re a die-hard Pluto fan, you only have to wait 4 more years). And yet there is still much to see, much to explore. Not every world gives up its secrets easily, and perhaps none has been so difficult to probe than Titan, Saturn’s largest moon. Bigger than Mercury, second only to Jupiter’s Ganymede, Titan has an atmosphere of nitrogen so thick it has twice the Earth’s air pressure at its surface.

That thick, hazy atmosphere is impenetrable by optical light… but infrared light can pierce that veil, and the Cassini space probe is well-equipped with detectors that can see in that part of that spectrum. And after 7 years, and 78 fly-by passes of the huge moon, there are enough images for scientists to make this amazing global map:

Pretty awesome. And making this animation was a huge effort. First, not all of the passes were at the same distance, so scientists had to resize the images to match the scale. Cassini passed at different times of day for the local regions, so the sunlight angle changed, making illumination and shadowing different. The atmosphere of Titan is dynamic, changing with time, so again compensations must be made. It’s painstaking work, but the results are truly incredible:
(more…)

Mike Brown is an astronomer, specifically one who studies Kuiper Belt Objects, those giant frozen iceballs that haunt the solar system out past Neptune.

In fact, Neptune’s biggest moon Triton has a lot of characteristics similar KBOs — it may be one captured by Neptune — so observing it gives an interesting opportunity for a compare-and-contrast study. So this past weekend Mike was using the Keck telescope in Hawaii to observe Triton along with its (adoptive?) parent planet, and took this fantastic image of the pair:

[Click to poseidenate.]

This false-color image shows the two worlds in the infrared, specifically at a wavelength of about 1.5 microns, twice what the human eye can see. Methane strongly absorbs this color of light, so where Neptune (in the upper left) looks dark you’re seeing lots of methane clouds, and where it’s bright there are clouds higher up, above the methane. Triton is in the lower right, and is bright because it’s covered in ice which is highly reflective.

Now this is all very pretty and interesting and sciencey, but if you know me at all you know there’s more to this story.

Mike tweeted about the image, and I oohed and ahhhed at it, of course. But then he tweeted again, saying he was also observing Jupiter’s moon Europa, but it was too bright to get good images using the monster 10-meter Keck telescope. It "saturated the detector" which is astronomer-speak for "overexposed".

That’s funny, I thought. Neptune looks fine in the image, and the random noisy grain in it makes it clear Mike wasn’t anywhere near saturating the image. Now I know Europa is closer to the Earth, so it should look brighter, but geez, it’s a moon, and a lot smaller than Neptune. How could it be too bright to image?

It turns out my all–too–human and all–too–miserable sense of scale has failed me again. Math to the rescue!

(more…)