Category Archives: Astronomy outreach

astronomy, Astronomy outreach, galaxies, galaxy clusters, galaxy evolution

Peeking into Galaxy Clusters

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Gravitationally Bound Galaxy Collections Have Much to Reveal

Galaxies at the heart of the Virgo Cluster. This formation is called Markarian’s Chain. Courtesy Samuel Oschin Telescope/CalTech.

Some years ago, I had the privilege of being the science writer for the Griffith Observatory exhibit project. Griffith, in case you don’t know, is located in the Hollywood Hills of Los Angeles, and is one of the best-known observatories and landmarks in the U.S. It was a rare honor, and in the years since then, I’ve found out how unusual it is for ONE person to be responsible for undertaking such a project. I didn’t know how rare it was. I was just thrilled to be on the project!

Standing by one part of the Big Picture exhibit at Griffith Observatory.

One of the exhibits that really caught my imagination (and offered me incredible writing challenges) was a giant wall containing an image taken by the Samuel Oschin telescope called The Big Picture. It features a look at the Virgo Cluster of galaxies, a collection of that lies some 53 million light-years away from us, and contains somewhere between 1,000 and 2,000 galaxies. If you visit Griffith, you can sit in front of the picture for as long as you like admiring the galaxies, quasars, stars, and other objects captured in an area of sky that you can cover with your finger, held out at arm’s length. It’s an incredible experience, and it was my great pleasure to study that image for many weeks as I wrote the descriptive text (and a video script) to go with it. In the end, it was all about what we can SEE in that image, and there’s a lot to study.

Checking Into the Coma Cluster

There are many galaxy clusters in the universe, and as astronomers get more sophisticated instruments and telescopes online, they’re digging into these galactic families to understand what makes them tick. And, it turns out that in at least one cluster (and probably many more), understanding them hinges not just on what we see, but what we don’t see.  Dark matter likely plays a huge role in what we detect going on in these galaxies and clusters. Take the Coma Cluster, for example. It is about 321 million light-years away from us and contains at least a thousand galaxies. Probably more, but many of them are very difficult to see. Why would that be?

Some of the more than 800 “dark galaxies” detected by Subaru Telescope in the Coma Cluster. Courtesy Subaru Telescope/NAOJ.

The Subaru Telescope, located on the Big Island of Hawai’i, has been studying this cluster. Recently astronomers took a look at all the archival data and found something rather interesting: it contains mysterious “dark” galaxies. More than 800 of these faint, diffuse galaxies exist, situated in the heart of a busy galactic city. Many are similar in size to our home galaxy, so imagine our immense Milky Way, but darker and dimmer. Yet, there are still stars in these galaxies. In fact, there are scads of old stellar systems, which is interesting since gravitational interactions between members of the cluster can really disrupt star systems. By all rights, those older systems should be flung around by tidal forces.

So, what’s protecting them? The best answer is: dark matter. In these galaxies, dark matter outnumbers the amount of visible matter by 99 to 1.

However, the protection of dark matter haloes isn’t the only thing going on here. Astronomers saw few “new” stars in these galaxies, which means that they lost the gas needed to form new generations of stars. This occurred fairly early in these galaxies’ lives, not long after they formed. So, the evolutionary story of these galaxies is a mystery needing further insight. And the detection of dark matter raises a LOT of questions.

Why is there so much dark matter in them? What role did it play early in the galaxies’ history? And, when did the galaxies lose the ability to form new stars? Does the dark matter than plays a role in protecting the older stellar populations have anything to do with mass loss in their home galaxies? Lots of questions, and the answers will come from additional observations of these distant galaxies.

I love looking at pictures of galaxy clusters. I’ve seen many images of the Coma Cluster, and of course, revelled in the study of the Virgo Cluster. Are all the things happening in those galaxies also happening in the many other clusters astronomers study? What’s the REALLY big picture? Stay tuned!

astronomy, Astronomy outreach, astronomy-related products, communicating astronomy

Take a Crash Course in Astronomy

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My New Book is Out!

Did you ever take an astronomy course in school? The most commonly taken classes in college are usually called something like “Astronomy 101” and they’re designed to teach the rudiments of this amazing science. The courses give students an idea of the “jargon” of astronomy, the principles of things like planetary orbits, a general look at how stars work, the evolution of galaxies, and so forth. The finer details—that is, the astrophysics and cosmic chemistry of how stars work, etc. —are typically studied in higher-level courses that require more background in physics, and are usually taken by astronomy majors. But, if all you want to know is the general story of how things in the cosmos work, then Astronomy 101 is the perfect class to take. I helped teach some of these courses when I worked at the university during grad school, usually in the planetarium (a perfect place to do it!).

Astronomy 101 on my bookshelf. Put on on yours, too! Image by Carolyn Collins Petersen.
Astronomy 101 on my bookshelf. Put on on yours, too! Image copyright 2013 Carolyn Collins Petersen.

You don’t actually have to take a class to learn about astronomy. There are many fine places online to learn it, or you can buy a book and study at your leisure. As it just so happens, I’ve just written a book called—wait for it— Astronomy 101. It’s available at fine bookstores (both online and in bricks-and-mortar establishments) everywhere. I noted today that my most favorite independent book store, Denver’s Tattered Cover (yes, they ship anywhere!) has it on the shelves. Powell’s also has it, for those of you who patronize that fine store). Astronomy 101 is also on Amazon.  The publisher is Adams Media, and I’m sure they’re working to get it in as many bookstores as possible.

If you’re teaching Astronomy 101 (or similar beginning course), this could be a useful (and affordable) addition to your students’ reading list.

When the editors at Adams came to me with the idea last year, they wanted a book that you could pick up and read a thousand words on a topic in astronomy and space science. They knew that readers see terms like “warp drive” and “black holes”. Readers hear about famous scientists like Edwin P. Hubble, Vera Rubin, Mike Brown, Copernicus, Galileo, and many others, but don’t always have the time to want to read textbooks to learn about these things.

So, my editors wanted me to give a fine first taste of astronomy.  They already had the title picked out, Astronomy 101, to let readers know the level of reading, and they had a subtitle picked out: “A Crash Course in the Science of Space”. And, the other subtitle “From the Sun and Moon to Wormholes and Warp Drive, Key Theories, Discoveries, and Facts about the Universe” tells the rest of what this book is about.

Those were the guiding principles I used to write the book. And, even with that guidance, it was tough. That’s because there’s SO MUCH to tell you about in astronomy and space science! I’ve been writing this blog since 2002 and I’ve never run out of things to write about!  So, figuring out what to write about, how much tell about it, and what I could leave out, was the hard part.

The fun part was simply writing down all the ideas I’ve had over the years about astronomy, the things I’ve learned in a lifetime of study and research and reading, and conceiving of a coherent way to introduce readers to the whys, wherefores, and personalities involved in doing astronomy.

I also had a fine group of readers—my astronomy posse—who sat in the background reading  each topic as I finished it. They patiently pointed out new findings, suggested rewrites in various places, and red-circled errors.  To them I owe a huge debt of gratitude—they are the experts in their fields and they were willing to help me tell the story of the science they love.

That’s the story behind Astronomy 101: A Crash Course in the Science of Space. I’m pleased that it’s finally out there, and I’d love it if you’d buy a copy. Review it online somewhere. Let me know what you think!  And, above all, come along with me as I explore the cosmos!