Date: June 4, 2011

Title: Encore episode: What is Astronomy?

Podcaster: Carolyn Collins Petersen

Organization: Loch Ness Productions
Music by Geodesium (

Description: Carolyn Collins Petersen, TheSpacewriter, discusses the science of astronomy and a few of the other science disciplines that cross paths with astronomy: physics, chemistry, geology, and biology.

Bio: Carolyn Collins Petersen is a science writer and show producer for Loch Ness Productions, ( a company that creates astronomy documentaries and other materials. She works with planetariums, science centers, and observatories on products that explain astronomy and space science to the public. Her most recent projects range from documentary scripts, exhibits for NASA/JPL, the Griffith Observatory and the California Academy of Sciences, to vodcasts 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 Riley, Drew and Brady Collins–three boys who love everything to do with space.


What is Astronomy?

This is Carolyn Collins Petersen, the Spacewriter, with some thoughts about a very simple question: what is astronomy?

Astronomy is the scientific study of the stars, planets, and galaxies that make up the universe. Astronomers study the characteristics of objects in the universe. They chart the processes that create, affect, and ultimately recycle – the objects we see in the sky.

I’ve often said that the science of astronomy is easy to do – all you have to do is go outside and look up! You see things in the sky and you marvel at how beautiful they are.

Eventually you want to know what it is that you’re seeing. You ask questions: what are those points of light? How far away are they? Why do I see certain stars during summer but not during winter? Why does one point of light look different from another? What is the nature of the Moon? The Sun? What’s that smudge in the sky – that dim little glow?

I think all of us who are interested in astronomy go through that questioning stage. And, to be honest, many of us never leave it. We just expand the stage to learn more about what we’re seeing in the sky. And, that’s where astronomy becomes something bigger, more complex, and actually–more exciting.

Astronomy plays an interesting role in science – and, in fact it’s often referred to as a gateway science. This is because it doesn’t live alone on the bookshelf of science research.

Doing astronomy can take you into other sciences – like physics, chemistry, geology, and biology, to name a few.

When we apply physics to astronomy, we’re into astrophysics. And that takes us into places in the cosmos we really can’t go – for example, the hearts of stars. Astrophysics helps us figure out the processes that cause stars to shine the way they do.

The light radiated by stars and galaxies, as well as the light reflected off of planetary surfaces and dust clouds, is a treasure trove of information. On first glance, if you look at a field of stars, you notice that some appear brighter than others. In astrophotographs, you may see that some stars are bluer, some whiter, some reddish, and so on. The colors and brightnesses – called luminosities – tell you something about the temperature of the stars, and maybe also about their distances.

Now, imagine that you take the light from oh, say, a star, and look at it through a special instrument – called a spectroscope– that divides that light into its component wavelengths. Well, you can find out a lot more about the star’s characteristics – its speed through space, its rotation rate, its exact temperature, and even the chemical elements in its atmosphere.

You can do the same thing with sunlight that’s reflected off the surface of a planet – say Mercury, for example. That light can be dissected the same way – that is, broken up into its component wavelengths of visible, ultraviolet, and infrared, and so on. The information you get by looking at Mercury in that reflected light tells you that some parts of its surface are volcanic in origin. Or, light reflected from the surface of an icy world in the outer solar system tells planetary scientists that that ice is made of water or nitrogen or methane, or that there are some impurities in the ice.

Breaking light apart into its component wavelengths is called spectroscopy, and it takes astronomy squarely into the realm of chemistry.

Chemists know the spectral fingerprints of all the elements in the universe. If you take a spectrum of a star or galaxy and compare it to the known fingerprints of chemical elements, you pretty quickly discover what those objects are made of.

What about the other sciences I mentioned? When we study the surface of a planet – say Mars, we first determine all the different surface units we see. We find craters and rift canyons and flood plains and volcanoes, to mention a few. The next step is to study the chemical makeup of the surface soil and dust. We also study the atmosphere. All of this is what geologists do here on Earth – and more.

People who study the same things at other planets are called planetary scientists. And their work is an important part of astronomy, too. Since planets are a by-product of starbirth and star death, astronomy is a path to geology and planetary science.

Finally we have biology. Here on Earth, biologists categorize and study all the life forms that exist on this planet. Beyond that, they study how life coexists, and beyond THAT, they research how it got started here. That leads them to ask a lot of questions about life elsewhere in the universe. Such as, when life got started here on Earth, what conditions did it need? Can we find those conditions elsewhere in the solar system? Can we find planets around other stars where those same conditions might apply? And, the big question: HAS life gotten its start somewhere else?
If so, what clues do we need to be looking for to figure out if it did?

Those questions are at the core of a science called astrobiology – the search for life and the conditions for life — elsewhere in the universe. To be an astrobiologist is to have your feet firmly planted in the worlds of biology AND astronomy – to better answer all those scientific questions about the origin and evolution of life in the cosmos.

So, as you can see—astronomy isn’t just about looking up at the stars. It’s way more than that. It starts there, sure – but I can think of no finer way to get a wonderful introduction to many sciences simply by doing astronomy – and just as importantly – by bringing a love of astronomy to our students, our friends, our children, our world. Science is not a compartmentalized political unit – it’s a living, breathing process of understanding the cosmos – and astronomy is an integral part of it.

For more about the sciences I’ve discussed here today, point your browser to and click on the 365 Days of Astronomy tab. Thank you for listening!

End of podcast:

365 Days of Astronomy
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