A sky full of awesome

I love looking up at the night sky. Whenever I’m outside at night, the first thing I do is look up. How can I not? But there’s always something marring my view – light pollution, clouds, the moon, treetops, and, oh yeah, the Earth itself! I’ve often thought how great it would be if the Earth, Moon, and Sun were to vanish and to be able to see the entire night sky at the same time*. How cool would that be? This cool:

Nick Risinger’s 37,440-image portrait of the entire night sky. The entire sky.

That’s the whole night sky. The entire. Night. Sky! This work of awesome comes to us courtesy of astrophotographer Nick Risinger’s Photomic Sky Survey. And wow, what a sky it is!

The first thing that jumps out is the Milky Way. Here, we see it just as it really is – a great spiral galaxy seen edge-on, or in this case, within the disk of the galaxy itself. In fact, it’s really no different than other spiral galaxies seen edge-on as well. At center is a well-defined bulge partially obstructed by dust silhouetted by the bright stars beyond. Toward the edges are the telltale populations of younger stars. In other words, your typical spiral galaxy!

To the lower right are the Large and Small Magellanic Clouds – two irregular-shaped satellite galaxies that orbit the Milky Way.

And there is so much more detail in this image. To experience it, you really want to check out the zoomable version. Seriously, click the link. Click it now!

If that wasn’t cool enough, check out the 360-degree version; you’ll feel like you’re floating in space! Make sure you are in full-screen mode. And maybe dim the lights – it’s that awesome.

How he do that?

To pull this off, Nick travelled more than 60,000 miles around the globe for the better part of a year taking no less than 37,440 exposures of the sky at night. But it wasn’t just a matter of simply picking a destination, going there and wait for the Sun to go down and shoot. Nick had to plan his destinations well in advance to find clear, dark skies and to be there when there during New Moon.

After a year, Nick then worked to stich together all 37.440 exposures to make this beautiful all-sky masterpiece. Nick has a really cool writeup of the project. His story is as fascinating as the image itself.

An app for that

If you’d like to appreciate Nick’s gorgeous work on the go, he has an app for iPhone and iPad available. If you prefer to just hang it on your wall, there are some rather nice prints available as well (my birthday is coming up…).

I really have to hand it to Nick Risinger for a tremendous effort and a spectacular result!

* Allowing, of course, for the ability to actually survive under those conditions

The Milky Way’s hot halo

It’s easy to think about our Milky Way galaxy all by itself out in space, surrounded by a halo of globular star clusters, some small satellite galaxies, and that nothing else except for its neighbors millions of light-years away.

But the reality is likely quite different. Our home galaxy may be surrounded by an extended halo more than three times he diameter of our Milky Way, like this:

Artist’s impression of the extended halo surrounding our galaxy. Click to enhalonate!

That’s our home galaxy at the center, and those two puffs to the lower left are the Large and Small Magellanic Clouds, which are two irregular-shaped satellite galaxies that orbit the Milky Way. But surrounding all three is a halo of hot gas that extends for hundreds of thousands of light years, and as hot as 1-2 million kelvin!

How they do that?

A team of astronomers used NASA’s Chandra X-Ray Observatory to observe eight bright X-Ray sources hundreds of millions of light-years away; much farther away than the extent of our own Local Group of galaxies. It turns out that the some of the X-Rays from these distant sources were absorbed by by ionized oxygen gas surrounding our galaxy.

The fact that the oxygen is ionized means that the gas itself must be very hot – between 1 million and 2.5 million kelvin. And the fact that this absorption is the same no matter which distant X-Ray source we look at means there is quite a lot of this gas surrounding the Milky Way. How much? Perhaps as much as 10 billion to 60 billion suns worth. That’s a lot of hot gas!

The hot halo (not to be confused with the warm halo)

Astronomers already understand there is a halo of cooler (anywhere from 100,000 to 1 million kelvin) gas surrounding the Milky Way. But these observations seem to imply there is a lot more hot gas making up a much larger halo, indeed.

Missing baryons?

Now to be clear, these results are not yet unconfirmed. It could be that no such halo exists, and the observations can be explained by some other phenomenon. That’s ok, that’s how science works. But if it turns out that the halo is real, it could help explain the Milky Way’s “missing baryon” problem.

Baryons are ordinary matter – things like protons, neutrons, elections – in other words, ordinary everyday matter. When we look at very distant galaxies, we’re looking back in time to see how they looked when the universe was one-sixth its current age. But when we look around in our own Milky Way and nearby galaxies, it turns out there is only about half as much of this baryonic matter visible.

This halo, if its real, would contain about enough mass to account for the “missing baryons.” They wouldn’t be missing at all, they’d just be in a very extended and diffuse cloud surrounding the galaxy!

And that’s a good thing, because the universe is mostly filled with weird and mysterious stuff like Dark Matter and Dark Energy as it is. Its nice to be able to account for some of it once in a while.