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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.

In Science News!

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.

Visualizing the Universe, Part V: 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.

Visualizing the Universe, part IV: Time to Get a Move On

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.

Visualizing the Universe, Part III: The closest star

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:

Visualizing the Universe, Part II: Parallax

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.

Visualizing the Universe, part I

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:

Quiet fall skies

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.

Lunar closeups

Here's an image from three days ago (June 29, 2009). This is a full-sized crop of the original. I've tweaked the image slightly (grayscaling to improve chromatic aberration, and a touch of unsharp masking), but the effects are cosmetic; you can still see the same details in the original. The smallest craters clearly visible near the terminator are less than 10 km across: for example, you can see Hyginus A, at 8 km, and it's clearly more than just a couple of pixels). Not bad for a $250 optical tube and a $250 compact non-DSLR camera. It's definitely better than the first few views of the Moon I got through a $3000 telescope 25 years ago!

After the deluge...

It's been a quiet few months thanks to rainy weather here in northern Colorado.

June 29 was the first day in 3 months that I got more than a quick look at the sky. As a result, it was more of a "summer showpiece" sort of night, full of big bright things like the 1st-quarter Moon, globulars like M13 and M3, and bright nebulas like M57 and M27.

Saturn, which I'd hoped to observe more in the spring, is finally on its way out; I saw it briefly, but only very low, with already poor seeing made worse by the altitude. I was hard pressed to see any moons besides Titan and Rhea, and no details on the disk itself.

I did get a few quick photos through the 100mm refractor:


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