December 7, 2013 at 10:00 am | Leave a Comment
The Milky Way’s Formative Years
How do you see a galaxy in all its stages of formation? You can’t watch it in real time because galaxies take millions or billions of years to fully assemble themselves. They form by assimilating each other, colliding, and interacting.
The only way to see a galaxy like the Milky Way form (for example) is to find galaxies at all stages of formation and take snapshots. Eventually, you get a series of views of how our own galaxy would have looked as it formed. (For what it’s worth, the Milky Way is still ingesting other dwarf galaxies, and it will likely gobble up the Magellanic Clouds and collide with the Andromeda Galaxy in the far future, so it’s really a work in progress.)
So, astronomers did just that: they found a lot of galaxies at different stages of their evolution, and put together this timeline of how our galaxy looked throughout its history. The galaxies are arranged according to time. Those on the left are nearby to our galaxy. Those at the far right existed when the cosmos was about 2 billion years old. The bluish glow from young stars dominates the color of the galaxies on the right. The galaxies at left are redder from the glow of older stellar populations.
To create this timeline, astronomers traced 400 galaxies similar to our Milky Way at various stages of construction over a time span of 11 billion years. They used Hubble Space Telescope and its sharp eye to peer out across the universe. The result taught astronomers a lot about how our galaxy built itself up. It turns out that our galaxy built up most of its stars (about 90 percent) between 11 and 7 billion years ago. It also means that our galaxy began forming only about a billion or two years after the Big Bang. All those billions of years ago, the Milky Way was likely a faint, blue, low-mass object. It had a lot of gas, which it used to create many new stars. When star formation began in earnest, it likely had a bluish color. The blue colors of the Milky Way ancestors are a signpost of rapid star formation. At the peak of star birth, when the universe was about 4 billion years old, the Milky Way-like galaxies in this timeline were pumping out about 15 stars a year, and our Milky Way would likely have been that active, too. By comparison, our galaxy today is creating only an average of one star a year.
Things will change in the future, when our galaxy collides with Andromeda. The gravitational interactions will fuel huge outbursts of star formation, and the night sky from our planet (if it’s still around), would be spectacular!
December 3, 2013 at 9:30 am | Leave a Comment
Welcome to Proxima Centauri
You know, someday humans are going to figure out how to travel to the stars at speeds that make such activity even more attractive than they are now. We do it in our dreams, via Star Trek, science fiction books, and movies. We already know about warp drive and other faster-than-light methods of travel. We just have to make them work.
One of these times, we’ll make it real. And where will we head? The nearest star could prove interesting. It’s called Proxima Centauri, and it lies about 4.2 light-years away from us. It’s not like the welcoming, yellow-white Sun we’re used to, however.
Proxima Centauri is a red dwarf, and so far, even using the good telescopes, astronomers haven’t spotted any supermassive planets around it (let alone Earth-sized ones). So, a trip to Proxima might be a quick fly by unless some hitherto unknown Earth-like world shows up in a future planet search.
Still, it would make an interesting study for the onboard astrophysics team of any interstellar spacecraft heading out “thataway”. Proxima is a low-mass star, and due to some pecularities in its core, it will burn through all its hydrogen, but likely won’t be hot enough or massive enough to fuse helium. This M-class dwarf just isn’t in the Sun’s league. But, it’s still a viable and interesting place to head out to on a first reconnaissance trip. You never know, it just might have some planets we haven’t spotted. If they’re there, then planetary scientists can start to think about whether or not they are in their star’s habitable zone and if they could support life. That’s the reason for exploring the universe isn’t it? To find other worlds, other civilizations…
December 1, 2013 at 8:30 am | Leave a Comment
Your Astronomy for Today: Our Star is a Star
The Sun is a star. That doesn’t surprise too many people these days (except for the usual anti-science, Earth-is-only-6,000-years-old crowd). Yet, for a long time, it wasn’t considered a star. Sure, there were were early Greeks who suggested it might be one, but they didn’t have a lot of luck getting that idea to be taken seriously. In fact, it really wasn’t until about a hundred years ago (or so) that humanity really had the serious scientific chops to measure the Sun, compare it to other stars, and come to the conclusion that it is a star.
Like other stars, the Sun has nuclear fusion going on in its core. That’s a process that takes hydrogen atoms and fuses them together (this requires high pressures and temperatures to achieve). The process creates helium, and releases heat and light. The Sun has been doing this since it first turned on, 4.5 billion years ago. It will continue to fuse hydrogen to helium for a few billion years yet. Eventually it will run out of hydrogen and start to fuse helium to make carbon. At the same time, gravity will cause the Sun to compress under its weight. At the same time, its atmosphere will start to expand to let off all the additional heat created when helium is fused. It will become a red giant for a time, expanding out to engulf most of the inner solar system and warming up the gas giants.
Eventually, the Sun will lost most of its outer atmosphere to space, and what’s left of our star will slowly contract to become a white dwarf. It will still be a star, just a tiny, massive, slowly cooling one.
And that, friends, is your moment of solar zen for today.
November 29, 2013 at 10:00 am | Leave a Comment
It Inspires Some Cool Gifts!
A few entries ago I talked about how astronomy is for everybody. It’s true, you know. The stars are humanity’s common heritage. They taught us to tell time, build calendars, and navigate the globe.
We came from the stars. I know I’ve talked about THAT before. All the elements in our bodies came from long-gone stars in a process that stretches back throughout the history of the cosmos.
So, if you’re looking around for something TRULY cosmic to give this holiday season (or anytime), consider a gift of astronomy. (Yes, I know it’s Black Friday (the big shopping day after Thanksgiving Day in the U.S.). I’m just offering an alternative to standing in long lines waiting to buy the latest “thing”. The products below are mail order, downloadable, and eminently cool!)
Of course I’m going to tell you about some cool astronomy products that I, personally, have been involved in. The first is my latest book, called Astronomy 101: From the Sun and Moon to Wormholes and Warp Drive, Key Theories, Discoveries, and Facts about the Universe. It’s available in both hardbound and e-book formats, and you can find it in bookstories everywhere and online. It’s even in Urban Outfitters, which never fails to delight me.
So, for the cost of a pizza or two (or a couple of grande-type drinks at your local coffee shop), you can get the universe, divided into topics of a thousand words each, written at a beginning (and engaging) level. Check it out! Make your loved ones happy (or yourself). Make ME happy. It’s the gift that keeps on giving!
If you’re into astronomy apps, then you can’t go wrong with Starmap Media. That’s another one I’ve been working on, in cooperation with the developer (a delightful guy who turned a fascination with astronomy charting into a business). Starmap Media is an iPhone and iPad app that combines an elegant star chart function with pre-recorded multimedia “star talks” (like you hear in the planetarium) that you can enjoy in real time under the stars or in “couch mode” when the weather isn’t cooperating.
I wrote the scripts for more than 30 of these stories, the developer produced them with original artwork, music, and a narration by veteran voice actor Jon Mohr (Mark and I also used him as the American voice for a planetarium show called Into the Deep, produced by Ogrefish Filmproduktions of Austria).
The resulting story productions have been described by some users as having a personal planetarium in the palm of your hand. They’re made for education, entertainment, and inspiration—all through your iDevice! So, check it out and make a deserving developer happy!
Finally (for this round of astronomy-related gift suggestions), I am always pleased to present the wonderful space music of Mark C. Petersen, doing his thing as a premier space music composer since long before any of those OTHER guys under the nom-de-studio, GEODESIUM. You can sample his works and find many good places online for downloads and mail order from the main Geodesium.com page.
No matter what you end up purchasing, always consider the gift of time to teach others about your love of the universe. It might be something as simple as teaching a friend about the constellations. Or taking your children to the planetarium for a show. Or, starting a blog about your observations of the night sky. The possibilities are endless, and you have an entire universe to explore!
I’ll have other gift suggestions as the holiday season progresses, so do check back!
November 27, 2013 at 9:15 am | Leave a Comment
It’s a Heritage Science
A few weeks ago I went to Poland for a meeting called “Communicating Astronomy with the Public.” It was a gathering of about 200 people who work daily in bringing astronomy to public audiences. I presented a video called Losing the Dark about light pollution, and was part of a discussion about dark skies heritage for our children. All of us attending know that astronomy is one of the oldest, and most-approachable of all sciences. It’s also a gateway science; if you study astronomy, you can’t help but end up studying physics, chemistry, life sciences, astrobiology, and geology.
Astronomy began when the first people had a chance to go outside, look up, and marvel at the sky. It wasn’t long before they figured out how to use the sky as a calendar, a timekeeper. Why would they do that? To predict the seasons, which for hunter-gatherers as well as farmers is an important thing to do. If you know what season is coming up and when it begins, you know when to plant, to harvest, to hunt certain animals. Using the sky became a matter of survival. Later on, the use of the sky became more ritualized and incorporated into religious aspects of life, but the calendar and time-keeping functions remained as part of the observational practice of astronomy.
It really wasn’t until the Renaissance that astronomy came into its own as a science. And, from there, it evolved with each astronomer who put his or her telescope to work. Today, we stand on the shoulders of many giants in astronomy, beginning with the ancient Greeks, to Copernicus, Kepler, Galileo, Herschel, Hubble, and many others too numerous to name here. We get our star names from Arabic astronomers, our massive catalogs of galaxies and other deep sky objects from Herschel, Messier and others. Our perception of the universe was changed by Hubble, using Henrietta Leavitt’s discovery of the period-luminosity relationship of variable stars and their changing brightnesses. And, today, there are perhaps 10,000 trained astronomers using the world’s telescopes to learn more about the cosmos.
But, there are hundreds of thousands of amateur astronomers, too. Some are quite expert at observing and own very good equipment. Others are backyard-type astronomers using binoculars or small telescopes to explore the cosmos. And many people are content to go out each night, look at some constellations and planets and stars and take in the beauty of the night sky.
Astronomy IS for everybody. We should be encouraging more astronomy in our schools because it’s such an easy entry to other sciences. And science-literate children grow up to be savvier adults participating in society. It’s not a stretch; it’s true. And astronomy is a heritage we need to keep sharing.
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Copyright 2013, Carolyn Collins Petersen
Image of Horsehead Nebula: T.A.Rector (NOAO/AURA/NSF) and Hubble Heritage Team (STScI/AURA/NASA)
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