As Pluto learned in 2006, planetary status — like fame of any kind — can be painfully fleeting. Especially in today’s world, where new planets are being discovered at an incredible rate, and the very definition of a planet is in flux.
Brian Jackson, assistant professor in Boise State University’s Department of Physics, is in the second year of a three-year, $271,000 NASA Astrophysical Data Analysis Program grant aimed at finding and examining celestial bodies far different from what we think a planet should be. He is looking for planets orbiting much closer to their host stars than astronomers once thought possible — including one the size of Mars that zips around its sun in just four hours, an orbital period shorter than the extended version of “Return of the King.”
Thanks to NASA’s Kepler Space Telescope, launched in March 2009 to discover remote Earth-like worlds, more than 4,000 possible exoplanets, or extrasolar planets, have thus far been identified beyond the borders of our solar system. Currently more than 1,000 of them have been verified as true planets and some could possibly support life.
That’s because when “gas giant” exoplanets (enormous orbs composed mainly of hydrogen and helium, such as Jupiter and Saturn) get close enough to their host stars, their atmospheres can be stripped off, leaving behind only their rocky cores very close to the stars.
In these cores, Jackson believes, lie answers to one of life’s biggest questions: How did we get here?
“In asking how planets form and evolve, it’s good to have a lot of examples,” Jackson said. “What we learn can help us understand the origins of our own planet.”
So how does a scientist discover and study planets that are light years away?
By looking for the shadow of a planet as it transits in front of its host star, the Kepler mission has found thousands of potential planets. Astronomers also can look for the subtle “wobble” of a star affected by the gravitational tug of an orbiting planet. The period and amount of wobble, when combined with the size of the planet’s shadow, can tell astronomers a planet’s mass, density and composition, which leads to greater understanding of a planet’s physical makeup.
That’s important, Jackson said, because “what planets are made of feeds our understanding of how they form. And that can even help us understand how life on the Earth may have originated. What chemicals were available? How long did it take to form the planet, and how long until life was able to start?”
Jackson has pondered these big questions since he was a kid watching Carl Sagan’s 13-part series “Cosmos.” The groundbreaking public television program addressed a wide range of topics including the origin of life and Earth’s place in the grand universe.
“I’ve always wondered about those big questions,” Jackson said. “Like, why are we here, how did we get here, and where are we going?”
The Kepler mission offered a unique opportunity to finally get some answers.
During its nearly four-year mission, the $550 million Kepler space observatory mission focused on finding possible habitable planets by looking at objects in the “Goldilocks” or habitable zone that is just far enough from the host star to be neither too hot nor too cold for life. A hardware failure ended the original mission early, but NASA cleverly re-engineered the telescope’s operation, reincarnating it as the K2 mission, which has already found new planets of its own.
Jackson is scouring the rich database from the Kepler and K2 missions for objects very close to their host stars — about 50 times closer than Mercury is to our sun (which is about 36 million miles and an 88-day orbit). Although these celestial bodies are too hellishly hot to allow for the possibility of life, they offer plenty in the way of data on composition and density.
That data should keep Jackson and his research colleagues busy for a long while. And that’s just fine with Jackson.
“I’m both flattered and excited that the state of Idaho and Boise State University are willing to pay me to think about these things and teach students and the public about them as well,” he said.
Jackson is working with researchers from the Planetary Science Institute in Tucson, Arizona; the University of Texas-Austin McDonald Observatory; and the Johns Hopkins University Space Telescope Science Institute. The group also may use Boise State’s Challis Observatory for a closer look at possible planets.
