Sunday, April 06, 2008

What a Little Starlight Can Do

4/7/08 – 4/13/08
by C. Zaitz

When you look up at the night sky, you may have an emotional experience from the sheer beauty of the stars, but you are having a physical experience as well. Your eyes are taking in photons of light streaming from distant objects that are undergoing intense nuclear fusion. You gotta feel that!

I’m being playful, but the truth is, starlight packs a punch. We get a host of information from a little starlight. For example, when we see Betelgeuse in the eastward shoulder of Orion, it beams down faintly peach colored light to us. From this light we can deduce that Betelgeuse is a reddish star. Rigel, in the foot of Orion, shines bright white, almost blueish. Rigel is called a blue star. Each star has its own designer color.

The faint splash of color we detect with eyes can be amplified by a telescope. Through one, you can really tell that Betelgeuse is a red star. From that we can deduce its temperature, size, age and magnitude, since there is a relationship between all these characteristics. That’s a lot of information from a little starlight. If we had eyeballs shaped like prisms rather than marbles, we would be able to see even further into the starlight. The light would spread out into a spectrum- a rainbow of colors! Even better, we would see shadowy bars in the pretty band of color which tells us what the star is made of. It turns out that each element in nature has a fingerprint, and it shows up as dark lines in the colorful spectra of the star. The pattern identifies helium and carbon atoms as accurately as fingerprints identify people.

Once we know what the star is made of, know its color and therefore temperature and magnitude, we can reconstruct the star’s story from birth, through midlife, and even death. We know that stars like Betelgeuse are the “Elvis” stars; they burn brightest and hottest, but have short lives and die spectacular deaths. They only live millions of years, endure supernovae explosions, and end as pulsars or black holes. This will not happen to stars like our Sun. Smaller stars don’t have it in them to explode. The best they can hope for after a life of billions of years is to shed their outer layers and die a more peaceful, wasting away kind of death. Neither scenario is lucky for any planets orbiting, but both are inevitable. And all fates are written indelibly on the light we get from the star.

One even more powerful aspect to starlight is that it contains the information and history of the star from birth to death, like an endless movie. The second the star “turns on” by fusing atoms, its shines at the speed of light and on the light is a record of the star at that moment. When Betelgeuse dies its inevitable explosive death, we will have to wait the 400 plus years it will take for the light from the explosion to reach us. But it will be worth the wait. In the light from the explosion will be written the story of the creation of new elements; in the death of one star a story of future stars begins.

Until next week, my friends, enjoy the view.