The Wide-field Infrared Survey Explorer was turned off a few months ago, but the science it did lives on. NASA just released a gallery of nine spiral galaxy images taken by WISE, and they’re lovely:

[Click to galactinate.]

Several of my favorite big, grand design spirals are there, like M51, M81, and M83. Note that since WISE only sees infrared light, these are false color images; the colors used are blue for 3.4 micron IR light, cyan for 4.6 microns, green for 12 microns, and red for 22 microns. The reddest light a human eye can see is very roughly 0.75 microns, to give you a comparison. In the images, star-forming regions are yellowish and/or pink, dust (in the form of long-chain organic molecules called polycyclic aromatic hydrocarbons) is green, and old stars are blue.

While looking over the images, I actually recognized the name of the one in the lower right: IC 342 (here’s a full-res WISE shot of it). This is part of a small group of galaxies near our Milky Way that is heavily obscured by dust in our galaxy. (more…)

The Wide Field Infrared Survey Explorer (WISE) is an astronomy blogger’s gift that keeps on giving. Observing huge swaths of the sky in the infrared, it sends back the coolest images! Behold:

Yeah, click that to get the most cromulently embiggened 4000 x 4000 pixel version.

Those two galaxies are M82 (top) and M81 (bottom), and are both about 12 million light years away, relatively nearby as these things go. They are the two biggest galaxies in the M81 group, a collection of galaxies much like our own Local Group (dominated by our galaxy, the Milky Way, and Andromeda). M81 and M82 are almost certainly interacting with each, having had at least one pass sometime in the past, and may eventually merge in a billion years or so. Maybe less. Currently, they’re roughly 300,000 light years apart.

WISE sees them in the infrared, and in this picture blue represents the infrared wavelength of 3.4 microns, cyan is 4.6 microns, green is 12 microns, and red is 22 microns. For comparison, the reddest red your eyes can see is less than 1 micron, so these are well out into the IR.

Obviously, M81 looks very different than M82! M81 is a classic grand design spiral, roughly the same size or a bit smaller than the Milky Way. Most of the light you see comes from stars, which are bright at the shorter IR wavelengths.

M82, on the other hand, is a mess. (more…)

Astronomers are like forensic investigators. We have all this data taken from the scene of some sort of event, and have to piece together what happened. But those folks on CSI have it easy: they get to actually walk around the scene, poke and prod it, examine various stains, and even take physical evidence back to the lab. Astronomers are stuck standing a quintillion kilometers away, and we only get to see things at one angle.

But oh, what an angle. If it pleases the court, I’d like to enter this evidence for your consideration:

That’s my kind of evidence (click to embiggen). It’s an image of the lovely grand-design spiral galaxy M81, one of the nearest major galaxies to our own. At about 12 million light years away it’s bright enough to be seen in binoculars (and in fact some extremely keen-eyed observers have been able to see it with their unaided eyes). That means it’s close enough to study in detail… and what detail!
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M81 and M82 are bright nearby galaxies; you can spot them with binoculars easily in the northern sky, and they are a mere 12 million light years from us (for comparison, the Milky Way Galaxy is 100,000 light years across, so if you think of the Milky Way as a DVD, M81 and M82 would be about 14 meters away). These two galaxies interacted a couple of hundred million years ago, and the gravitational interaction drew out long tendrils of gas (which is very common in colliding galaxies).

Astronomers examined this bridge of material using Hubble, and found clusters of stars in it. That was totally unexpected; the gas was thought to be too thin to form stars! Amazingly, many of the stars are blue, indicating they are young (blue stars burn through their fuel much more quickly than redder stars. This means that the gas is still forming stars, even 200 million years after the collision!

In the image below, almost all the stars you see are young blue stars formed in the aftermath of that titanic collision. The reddish stars are stars in our galaxy, and the bigger objects are distant background galaxies.

Most likely, the stars formed when turbulence in the tendril caused local regions of denser gas, which could collapse to form stars. Before these observations, it wasn’t really thought it was possible to form stars in the regions between galaxies, so this is an interesting new find.