Friday Cat Blogging

June 30, 2006 at 14:56 pm | 1 Comment

What’s the cat constellation? Lynx? Leo Major? Leo Minor? All three actually, giving the cat family some permanence among the stars. So, in honor of cats in space, I present the space cats here at in honor of Friday Cat Blogging!

Pixel, named for the Cat Who Walked Through Walls

Pixel, named for the Cat Who Walked Through Walls

I have this theory that cats will rule the spaceways someday. They seem made for space travel, as long as you make sure there’s enough cat food (and, of course, a sandbox) for their needs. Those are things I thought about when I wrote Larry Cat In Space (one of the most popular planetarium shows I’ve done 28-plus years of doing this). We got the cat some food for his journey, but sort of forgot about the sandbox. Next time we’ll do better!

Anyway, here’s to the Friday Cats!

Lazarus Long, Laz for short. Named for a famous Heinlein character.

Lazarus Long, "Laz" for short. Named for a famous Heinlein character.

Miranda, named after a moon of Uranus

Miranda, named after a moon of Uranus

What Happened to Her Dream?

June 28, 2006 at 12:17 pm | Leave a Comment

I was going through my filing cabinets recently and found a series of letters I got back in the late 1980s from a young woman in Zimbabwe. I’m not sure how she found me, but she wrote to ask me how she could become an astronaut. All her life, she wrote, she loved the stars. She used to go out and make up her own constellations, in addition to the stories her people (the Shona) told about the stars. Once she even sent me several pages of drawings she made of the night sky, the stars all connected with lines to show me her constellations.

I sent her some astronomy books and encouraged her to keep studying science as long as she could. She didn’t have a lot of hope that she’d be allowed to study astronomy since her country needed doctors and computer programmers and more “practical” scientists before it needed astronomers. Eventually we lost track of each other, and in the years since, Zimbabwe has fallen onto very hard times under its current government. So, I don’t know what happened to my friend. I hope that she has been able to persevere and study science, and that she looks out at the stars and still does her astronomy. And, now that I think about her again, I’m going to do a little searching out of Shona and Zimbabwean understanding of the stars and the cosmos.

Spaceports and Dome Futures

June 25, 2006 at 14:45 pm | Leave a Comment
Delta launch, June 21, 2006. By Carolyn Collins Petersen.

Delta launch, June 21, 2006. © 2006 Carolyn Collins Petersen.

We went to a planetarium meeting this past week. There are several each year in various parts of the world, and this one was in Florida in Cape Canaveral. As you might expect, the talk of the meeting was all about planetarium presentations and techniques, along with a good smattering of other topics. We also had a chance to see a Delta rocket launch, carrying a satellite into space. I do like seeing launches!

One of our guest speakers this past week (and our speaker list included people from KSC and JPL, as well), was Phil Plait, known to many as the Bad Astronomer. His website (Bad Astronomy) is a great place to read about astronomy, space science, and the crazy theories and ideas that people come up with and claim as “science.” Phil’s an old friend and I thoroughly enjoyed his talk on Friday night. If you ever get a chance to hear him, make the time.

Space shuttle Discovery on the pad, June 22, 2006 By Carolyn Collins Petersen.

Space shuttle Discovery on the pad, June 22, 2006. © 2006 Carolyn Collins Petersen.

I left the meeting wondering what our next steps in space will be. Interestingly the history of planetariums in the U.S. is tied quite closely to the rise of the Space Age. These unique round rooms are changing though, just as our space exploration is morphing into something possibly unrecognizable. Shrinking funding hampers the vision we need to continue space exploration at levels once promised by our first achievements in space. The same thing happens to planetariums, which are also morphing before our eyes. Sure, we’re still going to space, sort of. We’re exploring Mars with robots and learning amazing things with Hubble Space Telescope (although with the possible loss of the Advanced Camera for Surveys and the “who knows if we’ll ever send the last servicing mission to HST” attitude among some mission planners, it’s hard to tell what HST’s future is now, even though it is still equipped with other working instruments.)

And sure, we’re still building planetariums, sort of. But many are closing down, just as NASA is having to choose between funding science and building out the space stations. No easy choices, there, either. New theaters are coming equipped with fulldome video, which forces many other, new choices on planetarium professionals. It’s a changing world, and this week’s meetings brought the changes in two of my interests—planetarium facilities and the U.S. space agency—into sharp focus.

June 16, 2006 at 22:20 pm | Leave a Comment
Comet Schwassmann-Wachmann 3 in a new light, Courtesy NASA/SWIFT/XRT/U.Leicester/Richard Willingdale.

Comet Schwassmann-Wachmann 3 in a new light, Courtesy NASA/SWIFT/XRT/U.Leicester/Richard Willingdale.

As Comet Schwassmann-Wachmann 3 continues what may be its final trip around the Sun(breaking up along the way), astronomers are turning everything they have toward it. While it isn’t as bright to the naked eye as Hyakutake or Hale-Bopp were a few years back, S-W3 is turning out to be dazzler in other wavelengths, most notably x-rays. In fact, it’s the brightest x-ray comet ever. The folks using the Chandra Observatory, the XMM-Newton satellite, and the Suzaku satellite (all three in orbit around Earth) are all getting ready to study the x-rays streaming off the comet.

The image above is what the comet looks like in x-ray wavelengths. It was taken using the NASA Swift satellite, which studied the comet recently. The data showed that the comet is about 20 times brighter in x-ray wavelengths of light.

How can a comet produce x-rays? It seems somewhat counterintuitive that such a cold, icy object would glow in wavelengths more commonly associated with hot, active events and objects. Astronomers are still characterizing the interactions that occur that cause cometary x-rays, but the basic story is this: as the comet plows through the solar wind, something called “charge exchange” occurs. Okay, that sounds appropriately mysterious, but what does it mean?

The solar wind is a stream of particles (electrons and protons). The comet is a lump of ices and dust. As it moves through the solar wind, those particles and gases fly away from the comet, particularly as the ices are warmed by the Sun. Those cometary bits are usually particles of molecules of water, methane, and carbon dioxide. When they the high-speed, high-energy particles from the solar wind encounter these lower-energy particles from the comet, electrons get “stolen” from the cometary chemical particles. In the process, a tiny bit of charge is exchanged and the result is a spark of energy, which results in an x-ray. So, it’s a collisional process that depends on an interaction between the comet and the solar wind. It’s not just from something the comet itself is generating.

Now, if you know enough about the x-ray energies that are given off in these collisions, you can make some deductions about the content of the solar wind and the makeup of the gases and materials being emitted by the comet. And this is one of the results of studying x-rays (and other high-energy emisssions) from such events as comets plowing through the solar wind.

Edgy Galaxy

June 15, 2006 at 10:18 am | Leave a Comment

One of the most fascinating things about astronomy is the incredibly rich diversity of objects we can study in the universe. Take galaxies, for example. These collections of stars fall into so many types, based on the shapes they have, that astronomers are continually sorting them into ever-finer “bins.” When I was first in school, we learned there were three basic galaxy types: spirals, ellipticals, and irregulars. Today, as we study more and more galaxies, we find that these gross distinctions do hold up, but within each category there are many variations, and what appear to be some transitional states between different types.

The galaxy M101, courtesy NASA/ESA Hubble Space Telescope.

The galaxy M101, courtesy NASA/ESA Hubble Space Telescope.

Spirals are pretty much what their name sounds like: roughly circular-shaped collections of stars, gas, and dust with arms spiraling in to a central core. We live in a spiral galaxy, and more than half of all galaxies observed are spirals. One of the most notable things (among many) about spirals is that they are studded with stellar birthplaces. Some spirals, including our Milky Way, also have black holes at their hearts.

When you look at a spiral galaxy in a full view, you can see the arm structure. In this image of M101, a spiral that lies about 26 million light-years away from us, you can also see soft, fuzzy looking regions in the spiral arms. These are clouds of gas and dust where stars form.

The other main type of galaxy is the elliptical. These are the ones that don’t have spiral arms and not a lot of other structure.They are simply large, oblong collections of stars with densely packed central bulges. Some have supermassive black holes at their hearts.

The big question, which does not have a simple answer, is how do galaxies get to be spirals or ellipticals? (We’ll leave out irregulars for now. They need their own entry sometime.) Does one type become another type in a sort of galactic evolution scenario? Is there a kind of galaxy that is somewhere between spirals and ellipticals?

The answers are far from complete. One scenario has spirals merging over billions of years to become ellipticals. It’s a complex one, and observations are giving support to the idea, because astronomers are finding galaxies in many stages of merger, and some of the resulting interactions seem to be making galaxies that look just like ellipticals. And, mergers are an important way that galaxies are assembled. Our own Milky Way is still “collecting” other galaxies smaller than itself in a case of cosmic cannibalism.

There ARE galaxies that look like they’re stuck somewhere between being a spiral or an elliptical. These are the lenticulars. They have disks like spirals, but their central bulges are more like ellipticals. If you view one edge-on, as we see in this Hubble Space Telescope image, it looks like a spiral viewed from the edge.

An edge-on galaxy: NGC 5866

An edge-on galaxy: NGC 5866

There is an intriguing element to this galaxy, and that’s the dust lane that seems to divide it in half. NGC 5866 also has a substantial collection of young blue stars in its disk, with older, redder stars at its heart. The only thing it doesn’t seem to have is spiral arms. But, those blue stars tell us that the galaxy has recently undergone episodes of star birth. Coupled with the fact that the disk is slightly warped, we have the possibility that this galaxy might have had some sort of gravitational interaction with another one (or more) a long time ago. That would explain the bursts of starbirth and the warped disk.

But why no arms? Did it once have them, along with rich regions of starbirth? If so, what happened to the gas and stars that used to be in the galaxy disk? If an interaction is the culprit, then it would have stripped out the gas and stars and somehow affected the structure of the galaxy. And that would give us with the edgy galaxy we see today. Stay tuned!

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Image of Horsehead Nebula: T.A.Rector (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA)

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