Daily Archives: July 20, 2010

astronomy news, cassini, cassini mission, evolution of galaxies, galaxies, globular clusters, omega centauri

Cassini Catches a Cluster

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Omega Centauri as Ring Backdrop

Well, this is kind of cool. The Cassini Mission out at Saturn happened to be studying the planet’s F ring and during the course of the observations caught view of the globular cluster Omega Centauri as it passed through the camera’s field of view.

The movie above is actually 13 images taken three minutes apart and then surgically joined together by the Cassini team to make the animation.  It clearly shows the cluster moving through the background.

Omega Centauri is really a spectacular naked-eye sight. It’s visible from throughout the southern hemisphere and lucky folks in more southerly parts of the northern hemisphere closer to the equator have a good vantage point for it, too. It has several millions stars packed into an area less than 90 light-years across.

The cluster lies about 15,800 light-years away from us, and is the largest of the globular clusters that are associated with the Milky Way Galaxy.  Omega Centauri may have played an interesting role in the evolution of our galaxy. Some astronomers suspect that it could have been part of a dwarf galaxy that was consumed by the Milky Way billions of years ago.  If this is true, then the cluster is what’s left of that galaxy’s core.  It’s an intriguing idea and one that astronomers are still researching.

On an unrelated note, if you’re a fan of the Carnival of Space, check out this week’s Carnival, written by Emily Lakdawalla.  Great stuff in there, including one of my own entries.

cosmic distances

Gazing Across Time and Space

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Andromeda’s Fuzzy Patch

The Andromeda Galaxy, taken by G. D. Clinch at Prairiehillfarmiowa.com.

The other night I went out around midnight to see what the skies looked like. We’d had a pretty major thunderstorm, which dumped some rain and then fled the scene, leaving behind starry skies.  The Milky Way was stretched overhead, and that looked pretty cool. From our location we make out the dark dust lanes, and since the Moon had already set, I had a good dark sky.  After gazing up at the Milky Way for a while, and checking out some of the star clusters near Sagittarius, I decided to hunt my old friend — the Andromeda Galaxy.

Now, the naked-eye view of the galaxy is certainly not as good as the image here. It looks very much like a fuzzy patch in the sky between the constellations Cassiopeia and Andromeda. These nights, I can spot it around midnight, after the whole area of the sky has risen up out of the Front Range light pollution and has cleared the mountains behind our area. It’s not spectacular to the naked eye, but that’s not what draws me to look at Andromeda again and again. The lure is the distance across which I’m seeing. This spiral galaxy lies some 2.5 million light-years away. The light from its millions and millions of stars have traveled around two and a half million years to reach my eyes.

If you think about it, the light that left Andromeda leapt out away from those stars around the time that our hominid ancestors (called Australopithecus) were still around — although their time came to an end about 2 million years ago, paving the way for humans (the genus Homo — which includes us) to evolve.  That’s a heck of a long time to our human way of thinking, but compared to the 13.7-billion-year-old age of the cosmos, it’s not so long.

This distance and time illustrate pretty clearly that space travel is a lengthy procedure. IF we could move at the speed of light and launch ourselves out to Andromeda, it would take US 2.5 million years to get there.

I actually explored this whole light-speed, traveling-time, distance relationship in a planetarium show documentary called Light Years From Andromeda. It was one of the first astronomy scripts I ever wrote — and has been through a couple of iterations in the years since then. But, even though I’ve updated the show, the basic story remains the same:  space is big, space is dark, and when you’re a light beam traveling between galaxies, it’s finally good to find a place to park.  At my eyes!