On Aug. 25, astronomers announced the discovery of three planets, the smallest ever seen outside our solar system, between 30 and 50 light years away. That made me wonder: how do astronomers find planets that far away? How do they know the planets they're seeing have never been seen before? Are telescopes so good now that they can espy a ball of rock, light years away? Come to think of it, what do astronomers do anyway -just sit around an observatory in a white lab coat and look through a telescope all night?
\I've never seen a university astronomer in a white lab coat,"" laughed Matthew Bershady, UW-Madison associate professor of astronomy. Nor does he typically gather data by looking through a telescope, he said, shattering another of my preconceived notions.
""We let the telescope collect the light, which we analyze,"" he said. The telescope feeds data into a computer; the astronomer then parses it for clues. For example, he or she may use the telescope to take multiple pictures of the same object, using different wavelengths of light each time, e.g. infrared, ultraviolet and X-rays.
""Each wavelength produces a different image,"" Bershady said. ""For example, radio waves find cold objects like hydrogen gas, while X-rays find hotter gases-sometimes hydrogen, but also iron and oxygen."" This information lets astronomers deduce what type of cosmic events occurred in that region, what bodies may have exploded to produce this type of residue. So astronomers don't actually look at planets through their telescopes the way we might use a telescope to look at the moon.
What about when scientists say they watch distant galaxies to learn how our solar system developed? In a person's lifetime, these galaxies don't change, right?
""Well, imagine you're studying how children develop,"" Bershady said. ""You can't watch kids from when they're in kindergarten until they graduate from high school because it takes too long. So you go to a school and study the kindergartners there, and first-graders, and so on through high school seniors, all at once."" Similarly, astronomers study different galaxies of different ages and merge all the data to piece together the chronology of the universe.
""Of course, continuing this analogy, the universe is full of high school seniors, but as we look for earlier grades, we can't see all the kids-just the tallest ones,"" he said. ""We can see the whole high school graduating class, maybe half of the middle school kids, and only one or two preschool kids who ate way too many Wheaties."" So astronomers have to rely on the few young galaxies they can find to draw conclusions about the history of the entire universe.
He also said there is a lot of glory in being an astronomer: in finding planets, asteroids or extremes, like the furthest object in the universe. Unfortunately for him, though, there will never be a Planet Bershady because even if he finds a planet, the International Astronomical Union gets to name it.
So how does an astronomer observe a planet and know it was previously undiscovered, that its presence has never been recorded in the literature before?
In earnest, Bershady replied, ""Ever heard of Google?""
Dinesh Ramde is a second-year graduate student in journalism. His column runs every other Tuesday. You can reach him at dramde@wisc.edu.
