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Physics Professor Discovers Two New Planets

March 4, 2014

Contact: David Mitchell

Red star in front of planet
Tau Gem may look similar to this artist's rendering of GJ1214b.

To find a planet, you first have to find a star that wobbles. Then you spend a lot of timein David Mitchell's case, 14 years observing the star to prove its movement results from the gravitational pull of an orbiting planet.

Mitchell, a physics professor, and his fellow researchers recently discovered two new planets, τ Gem b and 91 Aqr b. τ Gem b is 319 light years away, orbits its star in about the same amount of time it takes Earth to go around the sun, and at least twenty times as massive as Jupiter. 91 Aqr b is closer and smaller at 149 light years away, a 181-day orbit, and only three Jupiter masses. These are Mitchell and his group's fifth and sixth planets.

"Twenty years ago, we didn't know about any planets outside our solar system. Now we can say planets are common," Mitchell said. 

There are about 700 known planets in the universe. Physicists suspect there are many more, but the process of proving a planet's existence is time-consuming. Mitchell's group studies giant stars at the end of their lifetime. Only 36 planets have been found orbiting this type of star.

The relative youth of this area of physics excites Mitchell. "I showed up at the beginning of this field of astronomy that started at nothing. It's nice that I get to make contributions to that. No one else in the world has ever gotten data like we have. No one else in the world has seen the things we've seen," he said.

Over the years, many Cal Poly students contributed to the discovery by observing the stars Mitchell's group focuses on. "It's nice to get students involved in something they can understand quickly and jump into. It's a great way for them to Learn by Doing," Mitchell said.

Student research groups traveled to the Lick Observatory in San Jose, Calif. for a hands-on experience operating the telescope and cameras. They also decided which stars to target out of the many that Mitchell studies.

"The long-range goal we're interested in is life on these other planets. I think it's a pretty reasonable thing to be looking for," Mitchell said.

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