Upsilon Andromedae



This was the first multi-planet system ever found. When Debra Fischer and I discovered this three-planet system in our Doppler measurements from Lick Observatory in 1999 we were utterly stunned. To find the first planetary system ever was history before our eyes. Strangely, it has three planets, not just two. So we found a triple-planet system before finding a double-planet system.



(Image: NASA, ESA, and A. Feild (STScI))

70 Virginis



This was the first planet found that was in an elongated, elliptical orbit, not a circular orbit. When we discovered it in 1996, many people said we were wrong, because they assumed planets must all reside in circular orbits. This planet, 70 Vir b, was the first of a large class of Jupiter-size planets that reside in elongated orbits, showing that our own solar system is just one of many architectures of planetary systems.



(Image: NASA) Advertisement

Gliese 876



We announced the discovery of two planets in 1998. This was the first planetary system around a small red dwarf star. More importantly, the two planets have orbital periods of 30 days and 61 days, so that the inner planet orbits the star twice for every one orbit of the outer one. This was the first "mean motion resonance" in an extrasolar planetary system. The two planets gravitationally shepherd each other!



(Image: Mark Garlick/Science Photo Library)

Gliese 436



We discovered the first Neptune-size planet, Gliese 436 b, in 2004. We were delighted to find a planet of minimum mass 22 times that of Earth. At the time, this seemed to be an incredibly small planet. I personally spent two years developing the statistic basis for securing this discovery



(Image: Lynette Cook/Science Photo Library)