February 18, 2010 at 9:00 am | 1 Comment
Especially in Galaxies
One of the hot topics in astronomy these days focuses on star formation in the early universe and the formation of galaxies. We do know that the first stars began to form a few hundred million years after the birth of the universe in the Big Bang. The first galaxies assembled themselves shortly thereafter. Astronomers are searching out those first galaxies to figure out their star-formation rates (essentially, how many stars were born in them in a given time period), and — just as importantly — what those galaxies were made of. The first stars were made of hydrogen (and some helium) that was created in the Big Bang. Stars like the Sun (which have more metals in them) weren’t around at that time. That’s because Sun-like stars are of a later generation than the first stars. Those early stars had to be born, live, and die before sunlike stars could exist.
Why is this? Because the first massive stars had to evolve through all the stages of stellar life and then explode as supernovae. As they evolved, they created heavier elements in their nuclear furnaces and when those stars exploded, they scattered those elements (plus a few that got cooked up in the explosion) out to space. Those elements mixed with hydrogen gas clouds and eventually, new generations of stars were born. THOSE stars had more heavy elements in them. The galaxies that contained them ALSO had more heavy elements in them (and by heavy elements, I mean heavier than hydrogen and helium and lithium, which were abundant from the Big Bang forward).
So, astronomers looking back at the earliest epochs they can see, can observe galaxies forming lots of stars, but those stars aren’t very metal-heavy. Fast-forward to today (in cosmic time), and they see that “current” galaxies aren’t forming stars at quite the rate the early ones did. Why is this? It’s been a mystery. Do earlier galaxies crank out stars more efficiently? Or, do they have more raw material in the form of gas and dust available to make more stars? And, if so, do huge rates of star formation in the early galaxies mean that when they get older, they’ve run out of fuel and therefore don’t make stars as much?
Astronomers at the University of Arizona, led by Michael Cooper, looked at swaths of the early universe. They used data from an earlier study, where they surveyed about 50,000 galaxies. They then winnowed out a group of “average” galaxies and looked at them through a number of telescopes, including Hubble and Spitzer, and radio telescope arrays in France and California. By using this “multiwavelength” method of studying the early galaxies, the astronomers were able to find the cold gas clouds that supply the “stuff” of stars. Their data tell them that the early galaxies that were ancestors to our own Milky Way had a much greater supply of gas than the Milky Way does today. This means that they have been making stars according to the same laws of physics that govern the star-making machinery in the Milky Way. But, they’re making more of them in a given time because they had a greater supply of material.
One typical galaxy, named EGS 1305123, seen in this image as it appeared only 5.5 billion years after the Big Bang, has a huge rotating disk that measures about 60,000 light years across. That disk is stuffed full of cold gas and dust (the stuff of stars). The galaxy looks like how the Milky Way probably appeared more than eight billion years ago.
So, typical galaxies in the early universe were crammed with three to ten times more molecular gas than today’s galaxies have. Over time, they gave birth to stars, thus depleting the starbirth nurseries of the building blocks of stars. Star birth formation rates slowed down to the rates we see in today’s galaxies because they are running out of gas and dust.
Want to read more about this finding? Check out the University of Arizona news page!
February 16, 2010 at 14:30 pm | Leave a Comment
GO ahead, I Dare You
In light of all the recent nattering and chattering about the NASA budget and how the sky is falling because Constellation got axed (never mind that it was underfunded under the previous administration and might not have flown in the next anyway), and how Americans are being denied their rightful place in space, or — even worse — how we’re spending SOOOO much on NASA that other programs aren’t being funded, I’d like to point everybody to a very nice page put together by the New York Times that shows you just how our projected $3.69 TRILLION U.S. budget is going to be spent. I might point out that under President Obama, the NASA budget is due for some increase in some areas — notably R&D and outreach, both places that could stimulate growth and jobs as NASA works to create sustainable growth while eventually getting us into space on a regular basis.
Here’s a screen grab of the NYT graphical budget– go ahead and enlarge it. I want you to look at the lower right area, where I’ve highlighted a box in blue. That box is where NASA fits in. Not everything in that box IS about NASA — just some of it. Then, look at the whole budget picture and think about what it says about our country’s commitment to science, techn0logy, and education — especially compared to everything else in the budget. I mean, NASA and NSF and other science funding is less than the agriculture line item (which includes outreach, education, and crop insurance).
Food for thought, folks. Food for thought.
February 15, 2010 at 12:29 pm | Leave a Comment
Depends on Growing NASA Anew
This image of the space shuttle is one of the most evocative and beautiful I’ve ever seen taken on orbit. It says volumes about our ability to regularly visit space and establish a threshold beyond the confines of our home planet.
What does this image say to you? If you are one of the people who is concerned that the new direction NASA is headed is one that will bring an end to our exploration of space, this image may have an entirely different meaning than to someone who sees it as the end of an old era and the beginning of a new one. Regardless of your viewpoint, it’s a gorgeous and thought-provoking view of our presence in space.
For what it’s worth, I think that NASA needs to be redirected and guided into a more sustainable and less “grab some rocks and bring ‘em home” kind of manned spaceflight future. It’s been an ongoing struggle to define a human presence in space, especially given the challenges such a presence puts in our faces. Robotic missions, such as the Mars landers, the orbiters, the Voyager and Cassini and Galileo and MESSENGER and Magellan planetary probes are relative “easy” to do, compared to putting humans in space. NASA has had incredibly wonderful experiences with the robotic missions, and the images we get from HST, Spitzer, COBE, and so many other missions have revealed the wonders of the universe to us. We will continue to do these missions and explorations — they are returning wonderful science to us every day. The human missions and crewed explorations of the Moon and Mars and beyond? I say, let NASA get its new sustainable future goals in place, and let these people do their jobs. If politicians can keep their whining to a minimum (particularly those who are pandering to voters before thinking through the implications of what a sustainable NASA future can be), we might have a chance of getting a better and more robust crewed space program for our future. If you’re a voter with a whining politician, let ‘em know that they should become better informed before shooting off at the mouth. Urge them to support NASA’s future — even if it does mean a few short-term cuts and re-arrangements. And, while you’re at it, urge your congresscritter or senator to push for better science and technology education funding. If they don’t, they are relegating U.S. kids to second-class citizenship when it comes to science education and technology development.
February 8, 2010 at 17:32 pm | 1 Comment
Explore the Solar System
– but Bring Your Adventure Gear
Some years ago my friend and colleague Paul Hodge, Professor Emeritus of Astronomy at the University of Washington, wrote a book called Higher Than Everest: An Adventurer’s Guide to the Solar System, that took the reader out to some of the most dangerous, gorgeous, and adventurous places in the solar system. I gobbled that book up because I could sit there and read it and dream about what it would be like to visit those worlds. To be sure, it would be the most extreme touristic adventure you could imagine: traversing the baking hot plains of Mercury, finding a way to dip into the Venus atmosphere and study that incredible surface; exploring Mars; braving the extreme hazards of the Jovian and Saturnian systems; warming up to Uranus and Neptune; and making one’s way to Pluto and the hinted-at treasury of other worlds that exist beyond Neptune. It would be the trip of a lifetime, if only one could fit all of that into one lifetime!
Well, fast-forward more than a decade, and National Geographic TV has created a series called “A Traveler’s Guide to the Planets” that extends the adventure of planetary exploration into the video realm and really makes you feel like you’re there on those other worlds.
It’s a three-night series that begins on February 14th. The folks at Nat Geo were kind enough to send me copies of two of the programs (about Jupiter and Saturn, respectively, which air on the 14th) for preview. The presentations cover the exploration of the planets in a pretty exciting and visually stimulating way. For example, there are some really nice CG sequences set on Jupiter’s moon Io that look for all the world as if you’re standing right there, witnessing those volcanic eruptions against the backdrop of Jupiter rising over the not-too-distant horizon.
The presentations also include interesting interviews and commentary from planetary scientists like Torrance Johnson and Bob Pappalardo — both of who have worked extensively exploring the planets using remote probes such as the Voyager and Galileo spacecraft. Each hour takes you TO the planets, exploring via CG and animation just what it would be like to visit those worlds. That’s one of the coolest parts of the series — and I hope that “you are there” feeling will inspire people to learn more about the worlds of the solar system.
I’ve often wondered what our next generation of planetary explorers will find when they finally get themselves (or their spacecraft) “out there” again – with the newest instruments to help them gather data. I’m sure they’ll find wonderful things — as this series illustrates. I hope that at least some of the audience members who see these shows will be inspired enough to join those missions of the future! There’s much to learn from the past, as these programs demonstrate — and more to find in the years to come!
February 4, 2010 at 21:34 pm | Leave a Comment
Galaxies in the Young Universe
For a long time, well before the invention, creation, and deployment of the Hubble Space Telescope, classifying galaxies was easy for the closest ones and quite a bit tougher for the more distant ones. When I say “classify” I mean determining a galaxy’s size and shape and structure — its morphology. There are several main shapes: spiral, elliptical, lenticular, irregular — and within those classifications you get subclasses like barred spirals and so forth. There was also a class of galaxies called “peculiar” because they looked — well, peculiar.
Making out the shape of a distant, dim blob of light is difficult unless you have a really good, strong telescope able to look out through the guck. So, until we had such observatories as Hubble and Gemini and Spitzer and European Southern Observatory and others, it was easier to determine the morphology of galaxies that were easier to see. That also meant astronomers classified galaxies that were closer to us. Edwin Hubble, for whom the HST is named, developed a classification scheme that astronomers came to call the “tuning fork” diagram because it … looks like a tuning fork. Nearby galaxies were observed and fit into this scheme and that helped astronomers talk definitively about the structure and characteristics of, oh say, a barred spiral galaxy and compare it to the characteristics of an elliptical galaxy.
But, the burning question always has remained — what are more distant galaxies like? Do they follow the same morphological classification scheme? And if so, what does that tell us about the time in which they formed and in which we observe them? Remember: when we look at distant galaxies, we are seeing them as they appeared very long ago. Looking at a galaxy that is six billion light-years away only tells us what it looked like roughly six billion years ago. Did galaxies conform to the same kinds of shapes they do in the closer and more recent universe? That was a question that modern telescopes were designed to answer. Scientists used data from both Hubble Space Telescope and the ground-based Sloan Digital Sky Survey to create a tuning fork for the more distant universe. The image above shows the tuning fork for the local galaxies in the top section. The bottom section is a classification of more distant galaxies that lie some six billion light-years away.
Even just a quick look at the image will show that the nearby galaxies — also known as the “local universe” is mostly (about 72 percent) spiral galaxies. Another 15 percent are lenticular (labeled S0), and only three percent are ellipticals (indicated by the letter E).
Now, look at the bottom half of the image and you see that among the galaxies as they existed half the age of the universe ago, there are way more peculiar galaxies (more than half, actually). Ellipticals are just about four percent, 31 percent are spirals, and 13 percent are lenticular.
Astronomers think that many of the pecular galaxies will evolve to become spirals through galaxy mergers. That process of interaction and merger is how the Andromeda Galaxy was formed, and indeed, our own galaxy is in process of gobbling up smaller, dwarf companions.
So, what’s the take-away message from this work? There are a couple: Classification is more than just make-work. Classification helps us trace the history of galaxy formation. Ultimately, it brings us back to the present-day universe and helps us understand why it looks the way it does. If you want to read more about the observations behind this result, check out the Hubble Europe web page story.
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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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