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In the last entry, I referred to a star that astronomers studied to understand its chemical makeup in an effort to figure out where it came from. That raised a question about how astronomers figure out the chemical makeup of a star.
They use a technique called spectroscopy. That's really a $25.00 word that means "breaking the light up into its wavelengths" and then comparing the data to the spectral fingerprints of known chemical elements. This is something that chemistry folks (who study the elements in the universe) do all the time, and a technique that let astronomers look at the radiation emitted from an object in space in new ways. It's fair to say that when astronomers began using spectroscopy to study stars and galaxies, the science of astrophysics took a huge leap forward.
Astronomers use specialized instruments called spectrographs, which were first used by chemistry researchers to study the spectral fingerprints of elements in the lab. (Read more about them here). Astronomers employ spectrographs to break up the light from stars, galaxies, planets, nebulae, etc. into its component wavelengths. The data from these instruments is then plotted, which lets the researchers analyze the chemical signatures in the light and compare them to the signatures of known elements.
The "prism" view of a spectrum of a star with hydrogen in its atmosphere might look something like the images below. The top image shows what it looks like when hydrogen absorbs light as it is emitted from an object. This means that hydrogen exists in or near the object. The bottom image shows what it looks like if hydrogen is emitting radiation (while it is heated). Each chemical element has a unique absorption fingerprint.
Each element has a typical "absorption" pattern that shows up in the spectrum of a star where the element exists. An object in space can also have an emission spectrum, which tells us that some element is being heated and glowing brightly. There's a rather nice tutorial about spectra here if you're interested in learning more about them.
So, the short answer to the query about how the astronomers figured out the chemical makeup of the star HE 0437-5439 is, they studied the light it radiates and compared what they found to the known chemical signatures of elements, particularly metals. They then compared THAT information to spectral studies of regions in the LMC. From that, they can draw a pretty good assumption that the star came from that region.
One other thing about spectra: you can also tell an object's velocity through space and the direction it's traveling, all using spectra. There's a gold mine of information locked away in the light and other wavelengths of radiation being emitted from objects in space. It's an amazing treasury that astronomers tap into every time they study an object through a spectroscope.)
A hundred countries (and counting) have signed on to participate in the International Year of Astronomy, which runs throughout calendar year 2009. The IYA planners envision the year as a time when people take renewed interest in astronomy and science, from school children to members of the general public and the astronomy community (both professional and amateur).
On their web page the International Astronomical Union, which is spearheading the organization of IYA 2009, states:
The vision of the International Year of Astronomy (IYA2009) is to help the citizens of the world rediscover their place in the Universe through the day- and night time sky, and thereby engage a personal sense of wonder and discovery. All humans should realize the impact of astronomy and basic sciences on our daily lives, and understand better how scientific knowledge can contribute to a more equitable and peaceful society.
Now, we're a planet full of people, all with different languages, philosophies, levels of income, education, science interest, and political backgrounds. How can astronomy be something we can all appreciate? It's pretty simple really: we all have access to the sky. There isn't anywhere on Earth where you can't look up and see the sky, day or night. Granted some places have hazy, light-polluted skies. But, even in the worst places, you can see a few stars at night or the Sun, or the Moon. Astronomy is universal.
And that's the beauty of International Year of Astronomy. Anybody can do something with it, as long as it's related to the "Cornerstone Projects" that the IAU and IYA planners have developed. What are those projects?
100 Hours of Astronomy
The Galileoscope
The Cosmic Diary
The Portal to the Universe
She is an Astronomer
Dark Skies Awareness
Astro&World Heritage
Galileo Teacher Training Program
Universe Awareness
From Earth to the Universe
Developing Astronomy Globally
You can read more about these projects the IYA home page linked above. I'm particularly interested in the Galileo scope, the Portal to the Universe, and the She is an Astronomer projects. Check out the pages and see if there isn't a project that excites you to participate, in whatever way you can.
It has been 11 years since astronomer Carl Sagan died following a battle with myelodysplasia. To commemorate his loss, and more important, to celebrate his life, many of us are blogging about Dr. Sagan or putting comments about him on the http://celebratingsagan.blogspot.com/ blog.
To say that Dr. Sagan was a hero to a great many of us would be an understatement. For all of us who came to science popularization as a result of the phenomenal Cosmos series (created with Ann Druyan), who read his science popularization books, and who followed in his footsteps as writers and researchers, Carl Sagan was the foremost practitioner of science outreach and popularization. Simply put, he embraced and shared a passion for science and truth. Cosmos may have brought him to public attention in a very broad way, but it was hardly the first thing he did. Do a search on Amazon and you'll find an amazing number of products—books, music, DVDs, CDs, and so on—that he had a hand in creating (or that he inspired). All are still popular more than a decade after his passing.
One of his greatest hits isn't something that you can pick up at Amazon or download from iTunes. It's called the Voyager Record—a sort of audio-visual time capsule that recorded a brief moment of humanity's time in the universe. There are copies of this album on the Voyager 1 and Voyager 2 spacecraft, each of which is speeding out from the Sun, never to return. Whenever I think of Carl Sagan, I think of those albums. He headed up the committee that created them; he fought for them to be put on the spacecraft, and in some sense, they carry his vision of humanity (with all our brilliance and foibles) along with them.
The Voyager Record
I often wonder what Carl Sagan would say today, if we were still alive and watching the current rush by some short-sighted politicians in the world to dehumanize science and scientists. These "leaders" seem to care for little more than the next election, the next corporate donation, the next fundamentalist endorsement. Would he have to rewrite the book Demon-Haunted World, where he describes the fallacies of too much reliance on short-sighted religious prophets and the uneducated embrace of pseudo-sciences by people who fear science? Would he need to add on new chapters with examples of people who disregard their critical thinking skills just so they won't be bothered by uncomfortable truths about their leaders, their country, their planet?
I've had many "godly" people tell me that Carl Sagan hated religion, which of course is nonsense. Most times they haven't taken the time to read his works and understand his points. A careful reading of his works has showed me that Sagan wasn't about hate. He disliked, intensely, the way that many people willingly let others do their thinking for them. He disapproved of the silliness of pseudo-sciences and those who use science to promote nonscientific theories as a cover for religious indoctrination in the schools. But, hate people or religion? There's no proof of it. And science is all about the honest search for truth and the proof of it.
Carl Sagan's greatest legacy is and will continue to be the embrace of science and what it can tell us about the universe. How the cosmos works, where it's come from, where it's going, our place in it; those are things that science can tell us about. We have to be willing to do our part, too, by stepping up to the challenge and using science as the exploration tool that it is. And that, along with a record of images and sounds from our planet, is all a large part of what Carl Sagan left for us as a gift and a encouragement to explore our cosmos and all the ideas (whether uncomfortable or not) that exploration brings.
I was reading the label on the side of a package of fresh sliced pineapple today and it said, "Best if enjoyed by August 10, 2007." Being the literal type, I immediately thought to myself, "So, I can only enjoy pineapple? What if I'm not a big fan of pineapple, but I eat it anyway? Am I ordered to enjoy it? And why that date? Does it turn into slop on August 11?"
That got me to thinking about all the little "directives" that companies lay on us as we use their products. They go through great lingual contortions to avoid saying the bare truth, which is, in the case of the pineapple, "This stuff'll go bad if you don't eat it soon." (Which would be more sensible, and I'm all about being sensible, and critical thinking, and all that stuff...)
Anyway, when I read those disclaimers, I sense the fine touch of a personal injury lawsuit when I see things like that on product containers. So, then I got to thinking about what these same "safety" disclaimers would look like if applied to other things, like:
The Universe: objects in deep space are more distant than they appear. (for all you cosmic expansion fans)
The Sun: best if enjoyed by 8 Billion SSE (Solar System Era). (After that, it could start swelling and expanding, which spells doom for our planet.)
Earth: please use sensibly. (It's never too late to care for our environment. So far, it IS the only planet we have to live on.)
Nuclear Weapons: keep out of reach of children (self-explanatory)
Supernovae: contents may explode under pressure (you don't want to be within a thousand light-years of these things)
Star-forming regions: warning—construction ahead (or, drive carefully, children at play)
Gamma-ray Bursters: explosive content, handle with care (best if enjoyed at galactic distances)
Methane atmospheres: may be harmful if swallowed (similar to other known gas-rich regions, such as cre@tionist "museums," intelligent-design "think" tanks, radical partisan political meetings, etc.)
The Big Bang: accept no substitutes (so far it's the theory that best fits the observed data)
And, of course, one of my favorite speed-limit truisms: 186,252 miles per second: light-speed, it's the law!
UPDATE: After reading this entry, Mr. SpaceMusic thought those "sayings" were so clever I should do something with them. So, I did. You can get them on t-shirts now, through my Cafepress Store. I've created some unique designs using NASA space images and the sayings above. Each purchase tosses a buck or two my way to help support my website and my writing habit. Check 'em out!
In all my years of doing "outreach" and "research," I've never found one good answer to that question. It's more like there are about a jillion good answers. Ask the question in a crowd and you get answers like, "Planets." or "What came first, stars or galaxies?" or "Is there life out there?"
Back when I worked on the Griffith exhibits, one of the curators told me that there were six questions they heard the most from visitors:
Why do we have day and night? Why do the stars appear to move across the sky through the night? Why do we have seasons? How do the phases of the Moon work? How do eclipses work? What does the Moon have to do with the tides?
That makes sense, since these are things we can see most directly from our vantage point on the planet. Once you understand those, you are prepped to learn about motions of other planets, the stars, and galaxies. And, we do live in a universe that is constantly in motion.
During one of the press conferences at AAS a week or so back I thought about the questions people ask about astronomy, and contrasted them with the questions astronomers ask about the cosmos. They are complex questions, but no more or less important than the ones "non-astronomers" ask. For example, one set of press conferences focused on black holes. These grab public attention because they're such weird celestial animals. Most people want to know things like, "How do you detect them?" and "What's it like inside one?"
Well, actually, astronomers want to know those things, too, and we have figured out ways to detect them, and know where to look for them. The questions astronomers are now starting to ask are things like "Do they exist in the centers of all galaxies?" and "What properties of black holes tell us about how they form?"
Eventually they'll get the answers, which will find their way into public lectures where audiences can glean a little more about the universe as astronomers see it.
There's not one Big Question about the universe. It's more like a million, billion, trillion little ones that we seek to answer so that we can understand the whys and wherefores of the stars, planets, and galaxies that populate the cosmos.
When you think of dedicated amateur astronomers, David Levy is one of the most avid and encouraging observers out there. He embodies the true amateur, as in "one who loves" what he does and loves the stars and planets and comets (can't forget the comets!). I've been a friend and fan of David's for longer than I can remember; he's done me several kind favors over the years, and in return, I've always supported his work and recommended his books to people.
Thus, it was with some trepidation that I opened an email today telling me that David had a stroke recently. He's on the mend, and apparently he didn't suffer serious damage, but will need some time to recover. David's married to the wonderful and wise Wendee, who is busy caring for him as he gets better. Take a hop over to David's site and read more about these two wonderful people, and David's many contributions to astronomy.
The sites below belong to space and astronomy enthusiasts. I make every effort to check them and make sure they are still appropriate. However, I am not responsible for their content, nor do I endorse any of it by simply linking to them. As with all Web surfing, please exercise caution.
Adot's Notblog A fellow traveler blogger and astronomy enthusiast!
Astronomy Blog An astronomy blog pondering the big questions
—books, music, DVDs, CDs, and so on—that he had a hand in creating (or that he inspired). All are still popular more than a decade after his passing. 
