The science behind planetary exploration

Hundreds of new planets have been discovered in the past decade, in large part due to NASA’s Kepler mission, which has uncovered 1,790 new stars and 2,321 potential planets since its satellite telescope was launched three years ago. Sixty-one of those potential planets have now been confirmed. However, only one of them, Kepler-22b, may sit in the elusive “Goldilocks zone” — where it’s not so hot that all the water boils off and not so cold that the water is trapped as ice (like Mars). History Forty years ago, the search for planets meant snapping a picture, developing it and comparing that star field to previous photographs. The basic idea remains the same, except giant telescopes in space such as the Kepler continuously capture the sky, analyzing it with sophisticated software programs that continually evolve. In the past 20 years, there have been two ways planets have been discovered: Wobbling A star wobbles because of the gravitational pull of a planet that orbits it. A side-to-side movement is difficult to pick up, but if a star wobbles closer to Earth or farther away, it can be detected by the light spectrum of the star. “It’s sort of like a cop using a radar gun, except we don’t use radar, we use the light of the star itself, which has a signature that tells you whether the star is approaching or going away — if it goes back and forth, it must be orbiting something,” said David Hanes, head of Engineering Physics and Astronomy at Queen’s University. This wobbling is monitored over years to ensure a definitive pattern emerges. This technology has been going on for three decades; the data has accumulated, showing definite patterns, which led to the first couple of hundred newly discovered planets. Eclipses The other technique is to watch a star to see if it periodically dims. Scientists take that to mean a planet has crossed in front of the star. The Earth’s atmosphere can mess up the star’s brightness, but NASA’s Kepler probe orbiting our planet is armed with a giant telescope clear of atmospheric interference. “If you see one dim a little bit, you might say, ‘Aha, we may have a planet here,’ but you’d want to wait and see that happen more than once,” Hanes said. And from Newton’s Laws, the star and planet’s sizes and masses can then be calculated. Life beyond Mars? One of the first steps to discern whether life as we know it exists on some of these planets is the presence of water, oxygen and carbon. Scientists can tell by analyzing the spectrum of light emanating from one of these planets. But finding water doesn’t prove anything about life — it proves that water-based life could be there. There is frozen water on Mars, but no proof of life. “The one thing that would be a telltale sign is if you could analyze the light from a planet and discover evidence of free oxygen in the atmosphere, which is almost certainly a sign of life,” Hanes said. But that would require a giant telescope, focused on a single planet, that is eons ahead of the Hubble telescope. It would need better resolution to be able to discern more subtle light patterns. That may be possible with the James Webb Space Telescope scheduled for launch in 2018. However, despite the Kepler success, political support has waned for such expensive endeavours. The Obama administration veered from the goal of sending astronauts to Mars, which would have used up much of NASA’s budget. Despite Canada’s history of space research, funding is also evaporating in Ottawa in favour of more concrete science. “The federal government wants the National Research Council to build better toasters to outcompete the Chinese,” Hanes said.