Date: January 29, 2011
Title: Light from Distant Galaxies
Podcaster: Carolyn Collins Petersen
Description: Carolyn Collins Petersen, TheSpacewriter, talks about distant galaxies and how they’re telling us about the early universe.
Bio: Carolyn Collins Petersen is a science writer and show producer, as well as vice-president of Loch Ness Productions, (http://www.lochnessproductions.com/index2.html) a company that creates astronomy documentaries and other materials. She works with planetariums, science centers, and observatories on products and projects that explain astronomy and space science to the public. Her most recent projects include documentary scripts, exhibits for NASA/JPL, the Griffith Observatory and the California Academy of Sciences, video podcasts for MIT’s Haystack Observatory and podcasts for the Astronomical society of the Pacific’s “Astronomy Behind the Headlines” project.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Carl Baker because the the study of astronomy helps us understand our place in the cosmos and promotes critical thinking.
This is Carolyn Collins Petersen, TheSpacewriter. In this episode of 365 Days of Astronomy, I’m going to talk about distant galaxies.
We live in a remarkable time in human history – a period when we are finally able to extend our vision out to some of the farthest reaches of the universe.
It wasn’t all that long ago – on human timescales – when all we knew about the cosmos was defined by what we could see with the naked eye. When we thought the objects we saw in the sky were mysterious, maybe even gods… or other mystical creatures that we humans dreamed up because we had no other way to explain them.
Well, we’ve come a long way since those days when superstition, ignorance, and fear ruled our perceptions of the cosmos.
Just in the past few hundred years, the scientific study of the universe – called astronomy — aided by the invention of the telescope, the spectroscope, and other tools, has given us a new understanding of what we see “out there.” Of course, there’s a LOT more to learn – but at least today, rational people know what planets, and stars and galaxies are, and are beginning to understand our place in this expanding universe.
I was thinking about all this the other day as I was browsing through some galaxy images from Hubble Space Telescope and some ground-based observatories. I got to thinking about when I was first learning about astronomy as a kid. Back then, galaxies were the most exotic thing I could imagine. I didn’t know a lot about how they formed, or what their place was in the evolution of the universe. I suppose if I thought about that at all, I probably figured – in my childhood imagination – that stars got together and made galaxies, somehow. That was about all the hierarchy I could imagine. They just were out there in the sky – for me to marvel at in black-and-white images of the Andromeda Galaxy and the Whirlpool Galaxy that were available from such places as Palomar and Mt. Wilson.
As I grew older and learned more about astronomy, I learned that galaxies exist in groups called clusters – and that clusters of galaxies are grouped into superclusters.
When I went to graduate school in the early 1990s, I remember going to a seminar on galaxy formation and learning that many aspects of galaxy evolution were still an open question for astronomers. The questions they were shaping as they made plans to study early galaxies with Hubble and other observatories were really fundamental: when did the first galaxies form? How did they form? And, what about those msyterious merging galaxies? What role do they play in galaxy evolution?
The story of how the galaxies we see today formed — such as the Milky Way or Andromeda — is one that astronomers call the “hierarchical picture” of galaxy evolution.
We now know the very first galaxies grew individually and rapidly in the early universe. They formed as early masses of matter and stars were pulled together into regions of higher density that astronomers refer to as “overdensities”. These infant galaxies were in place by about 400 million years after the Big Bang and dark matter continued to play a role in the continuing mergers of smaller galaxies into larger ones.
By all accounts, it was a fast build-up, and in these merging galaxies, astronomers today are seeing incredible rates of star formation that took place. The merging galaxies were popping out new stars like strings of firecrackers. And those early stars blazed with energy that we detect today with infrared-sensitive instruments such as those on Hubble Space Telescope.
These early mergers and acquisitions pushed the chemical and morphological evolution (that is, their changing shapes) of galaxies throughout time. The Milky Way and Andromeda and the Whirlpool and so many others are all veterans of this evolutionary process. The Milky Way itself is still undergoing some merger activity. Astronomers have detected streams of stars from small dwarf galaxies that are merging with our own.
So, if today’s galaxies are all products of mergers of older, smaller galaxies, we need to track back across time and space to a point when the earliest “building blocks” of galaxies were forming. And this is, in fact, what astronomers are doing – looking for the most fundamental galactic building blocks in the universe.
In the quest for those building blocks, astronomers are using all the tools at their disposal to see back to a time when the first galaxies were taking shape. So far, they’ve seen some very young ones.
On January 26, 2011, astronomers announced the discovery of the most distant galaxy ever seen. It lies 13.2 BILLION light-years away. Think about that: the light from that galaxy traveled across13.2 BILLION light-years. And think about this: our universe is 13.7 BILLION years old.
The light from that distant toddler galaxy is part of a study of very early galaxies in the universe. The data from that research is telling astronomers an astonishing story of galaxy formation at period when the universe was only a few hundred million years old – about the time the first galaxies were starting to merge with each other to former larger ones.
This newly discovered galaxy was found in a deep survey of the distant universe called the Hubble Ultra Deep Field. It was made with the Hubble Space Telescope’s Wide Field Planetary Camera 3. The galaxy itself looks like a faint smudge of light, and is tiny – extremely tiny, especially when compared to the galaxies of today such as the Milky Way, which is 100 times larger than this tiny precursor galaxy.
The astronomers who found this early galaxy also found three others in the data. But, the most important take-away from their discovery is that we now seeing galaxies some 13.2 billion light-years away, which means that they began to form in an even earlier epoch in the history of the universe – an epoch we have yet to see.
Can Hubble look farther into space and further back in time for us to see that epoch?
To see these earliest galaxies when they were just beginning to form, astronomers will use the upcoming James Webb Space Telescope. It will extend our view to even earlier epochs of time. Perhaps soon we’ll have much more definitive answers to the questions about the births of galaxies and the conditions in the infant universe that sparked their formation. Stay tuned!
If you’d like to learn more about the earliest galaxies and how astronomers are searching them out, point your browser to www.thespacewriter.com/wp and click on the 365 Days of Astronomy tab.
Thanks for listening and keep looking up!
End of podcast:
365 Days of Astronomy
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