People have puzzled over this since the earliest star-gazers sat in wonder beneath the night sky's twinkling sea of starshine. For at least a hundred years, scientists have been searching for other Earth-like planets that might have life-supporting environments. Recently, that search has taken them beyond our solar system's boundaries, into the mysterious world of exoplanets.

Exoplanets, also called extra-solar planets, are planets that revolve around a star other than our sun. In other words, they are planets that exist in solar systems located in other parts of our galaxy, the Milky Way. As of June 2009, there were 353 exoplanets listed in the Extrasolar Planets Encyclopedia (www.exoplanet.eu), an astronomy website founded in Paris, France in 1995, which contains a database of all known or suspected exoplanets.

Most exoplanets discovered so far, including 51 Pegasi b, have been found to be gas giant planets, mainly because the method that had been used to detect them — radial velocity — is much better at detecting gas giants than smaller, rocky planets. Radial velocity is an indirect method of observing planets because it doesn't actually allow scientists to see the planets themselves. Instead, it gives information on changes in a star's light emission pattern, which in turn provides clues that a planet may be orbiting around it.

NRC at the forefront...

On November 13, 2008, Christian Marois, an NRC scientist with the Herzberg Institute of Astrophysics, made astronomy history when he and his team had captured the world's first direct images of a multiple-planet solar system. The discovery was hailed by Science magazine as the second biggest scientific breakthrough of 2008, and ranked sixth by Time magazine among the top ten scientific discoveries of the same year.

Dr. Marois and his team used their innovative imaging techniques with the Keck and Gemini telescopes in Hawaii to observe three exoplanets, named HR 8799 b, HR 8799 c, and HR 8799 d. The planets are all roughly 10 times the mass of Jupiter. They orbit the star HR 8799, a star very similar to our sun, which is located in the constellation Pegasus. The HR8799 solar system is fairly close to our own: HR8799 is faintly visible to the eye and is only 130 light-years away.

NRC's Dr. Chritian Marois at the Gemini observatory in Mauna Kea, Hawaii.

According to Dr. Marois, what is so exciting about the discovery is that "it's all about understanding how planet Earth came to be. If we can find a planet with life-supporting conditions in another solar system, we could re-examine the theories about our own planet's formation and have a far better idea of the conditions that led to life here. The HR 8799 discovery brings us one step closer to this ultimate goal."