One of the great things about astronomy is how interested the public is in what we do. Whether it be pretty Hubble pictures, the Big Bang, black holes, or aliens, it seems that just about everyone always has lots of questions to ask.
What many people don't realize is that you don't need a space telescope or a PhD to participate in astronomy research. "Citizen scientists" (often called amateur astronomers) study variable stars, find new comets, discover supernovae, and look for extrasolar planets all the time. They help in the search for extraterrestrial intelligence and in classifying galaxies. They've even help us professional astronomers with our instrumentation. So much science wouldn't get done without the citizen science.
As part of the International Year of Astronomy 2009, a large observing campaign is being developed to monitor a strange variable star: epsilon Aurigae. Every one of you are invited and encouraged to help us study this strange star!
Epsilon Aurigae is a third-magnitude (moderately-bright) star in the constellation Auriga, the charioteer. Its name means that the stellar cartographer Johann Bayer considered it the 5th brightest star in the constellation (alpha Aurigae being the brightest, beta Aurigae the second-brightest, and so on.) Every 27 years, the star dims for about 650 days due to an eclipse.
Many stars dim regularly due to eclipses. Binary stars sometimes pass in front of each other (the star Algol in Perseus is one of the most famous examples), and many extrasolar planets were discovered by their eclipsing of a parent star. So, why are astronomers interested in epsilon Aurigae?
This star's eclipses are weird. Most eclipses last a few hours to a few days, but a 650-day eclipse is odd. In fact, the size of the object causing the eclipse in epsilon Aurigae would have to be much larger than any known star! Also, the shape of the eclipse is funny. Here's a plot of the brightness of the star NN Serpentis, a white dwarf star eclipsed regularly by a red dwarf star:
Image credit: European Southern Observatory
The brightness of the star drops pretty rapidly, hits a flat bottom, and then bounces back up to the starting level (the little up-and-down fluctuations you see are all errors in the measurements, not variations in the star itself). This is because the bright star is eclipsed by a fainter star; during the eclipse, we only see the fainter star. Now the light curves of eclipsing binary stars aren't always this dramatic, but they all look about the same: a smooth drop to minimum light, a flat or rounded bottom, and a smooth rise to the starting level. And, even more importantly, every eclipse is the same. Now, look at the light curve of epsilon Aurigae:
Image Credit: Citizensky.org
It has a long, jagged drop to minimum light, then gets a little brighter, then gets a little fainter, and then slowly and jaggedly gets bright again. And these jagged appearances aren't errors; they're real. Also, the length of the eclipse is changing, and has been getting shorter. Stars and planets alone can't make those variations! Something else is going on.
There are many ideas as to what is happening here, but with only one chance to get data every 27 years, these mysteries are slow to clear up. So, that's where you all come in. Starting in early August, epsilon Aurigae will begin to go into eclipse again. With careful observation, you should be able to notice the dimming of this star over several months with your own eye; if you have a telescope with a digital camera, this dimming should be easy to measure. AND, epsilon Aurigae is too bright to observe with most professional telescopes. In other words, citizen scientists can make just as much headway in understanding this star as professional astronomers can. And, even if you don't have a telescope, you can still use your own eye to see this mysterious star's eclipse. So, anybody can participate! AND, even better, since the eclipse takes hundreds of days, you won't miss much, even if you have cloudy skies for a week or two.