The Astronomy Nexus

I am hosting some of the larger downloads on this site on GitHub now. The most current version of the HYG database will always be posted there. Any publicly available code relevant to the site will go there as well.

It was clear for just long enough here in Colorado to get a good view of the eclipse. I got a number of decent shots with just a compact camera (Panasonic Lumix FZ-28, most at the max zoom level of 18x). As I've told a friend once, since the albedo of the Moon is similar to that of fresh asphalt, getting the right exposure settings for the full Moon is about as hard as getting them for a sunlit street. With an eclipse going on, it's a little tougher, but aggressive exposure bracketing solves many ills, and is very simple with almost any digital camera.

Here's one of my favorite shots (click to embiggen):

More images below the break:

The Distant Worlds Star Mapper has gotten a rewrite. There isn't a whole lot visible on the outside, but charts should get created a bit faster, especially if you have a lot of extra details (like constellation lines) turned on.

Science News has published one of my images from this site. The October 23 issue has an article about Gliese 581, discussing the potentially Earthlike planet discovered recently in its habitable zone. The image is a slight modification of the large chart in this post, showing the Sun among other stars as seen from Gliese 581.

The faint star Gliese 581 has been getting a lot of press lately: it's the first star known to have a fairly small planet in its habitable zone, or the region of space where liquid water can exist. Although we've found a few other planets in (or close to) probable habitable zones, they've been much larger. The recent discovery appears to be only a few times more massive than the Earth, rather than hundreds or even thousands of times more massive, as many exoplanets are.

What kind of star is Gliese 581? For one thing, it's not very much like the Sun. It's much dimmer. In fact, even though it's about as far away as stars like Fomalhaut and Altair, it's much too dim to be seen with the naked eye. Here's where it is in our sky. It's in Libra, not too far from the bright stars of Scorpius:

After the break, we're going to take a trip to Gliese 581 and look around.

One of the first groups of stars to be recognized as an actual group -- not just a chance alignment -- is the Hyades in Taurus. This is the closest major open cluster to the Earth.

This is what the Hyades look like now. They are the roughly V-shaped cluster near the bright star Aldebaran. However, although Aldebaran rounds out the "V" nicely, it's not a member of the cluster.

The Hyades are close enough that we have reliable measurements of the distances of its member stars, and we also have good measurements of the velocities of the stars as well, so it's possible to calculate its motion over time.

In the previous post, I showed how a nearby star -- Barnard's Star -- appears to move against the sky over time. Barnard's Star is the second closest to the Sun. The closest star (actually, the closest three stars, all bound into one multiple star system) is the Alpha Centauri system, at 4.3 light years away, about 2/3 the distance to Barnard's Star.

Alpha Centauri consists of three stars, two bright stars (both broadly similar to the Sun, called Alpha Centauri A and Alpha Centauri B) in a close orbit, and a third, much farther out, that is currently slightly closer to the Sun the the other two. This star, a very dim, red star, is sometimes called Proxima Centauri to emphasize its closeness to the Sun; it is the closest star to the Sun we know of.

Unsurprisingly, Alpha Centauri was one of the first stars to have its parallax measured. Since Alpha Centauri is closer to the Sun than Barnard's Star, it shows a larger parallax shift every year. Additionally, it is moving through space more slowly, so its proper motion is quite a bit lower (despite being closer). As a result, the parallax effects are easier to see with Alpha Centauri:

As you may know, people first figured out distances to the stars by measuring parallax shifts coming from the Earth's orbit. You may be wondering, though: given how far away the stars are, just what does this look like?

The first reliable measurements didn't come until the 1830s, over two centuries after the invention of the telescope and long after the discovery of Uranus, all the Messier objects, many faint planetary satellites, and subtle planetary details. As you can imagine, it's a fairly small effect that's difficult to detect. How small? More below the break.

When I haven't had time (or clear skies) to go observing the actual universe, I've been working on some ways to explore the virtual universe. A few years ago, I designed a basic starchart maker for this site that contains the entire Hipparcos catalog, so it could be used to show the sky from any location within a few hundred light years from Earth. I also found a bunch of stellar velocity data a while back, so for the brighter stars at least, I've been able to run simulations in time as well as space.

By creating a whole bunch of related images, I've created a number of animations illustrating various ideas from amateur astronomy, astrophysics, and even human archaeology and history. I'll begin with a short trip (in time, at least) to the Hyades, the closest large open cluster to Earth, right below the break:

I haven't been posting a lot lately, largely because a lot of the really quick updates go on Facebook these days. Despite all this, I've been doing a reasonable amount of observing lately. A few weeks ago I had an especially clear night where I could just see the largest dust lane in M31, the Andromeda Galaxy, in the 12.5" scope from the back yard. That was the first time in quite a while I remember doing that.

Last night was nearly as good. It brought a typical November Front Range sky: dark (at least outside of downtown), clear, and really bad seeing (forget about planets or close doubles). Fortunately, with Jupiter pretty much gone and the late fall sky segueing into the brilliant skies of early winter, there was plenty to see even so. M35 and NGC 2158 were beautiful, as usual: NGC 2158 is dim, but rich, and a real treat in the 12.5" even from a suburban location. (Give it a try even in an 8" or 10" scope; you may be pleasantly surprised!) The Big 3 in Auriga (M36, M37, M38) showed up well, and M1, the Crab Nebula, was distinctly more than just a faint oval, even without a filter. I told people I was going to see a few stars, and maybe a galaxy or two, but I ended up seeing four: M31, the Andromeda Galaxy, its two bright satellite galaxies, and the dim but still distinct arc of the late-fall Milky Way passing nearly overhead.