Scitech | Milky Way may be full of meat

Scientists develop new techniques to detect life on planets orbiting distant stars

Scientists have their sights aimed on planets teeming with alien life – their telescope sights, that is. In just a decade, astronomers have found over 300 planets orbiting distant stars, and a telescope due for launch in 2013 is expected to find many more.

According to Dr. Zachary Medin, a postdoctoral fellow at McGill, scientists are learning that planets are probably common throughout the galaxy.

“We’re finding that the number of stars with planets is pretty high. It could even be near 100 per cent of them,” he said.

Medin says that most of the 300 planets – called exoplanets – detected so far are behemoths, because distant earths are too small to detect.

“You can’t look at the planet directly; you have to look at the star. You can see a wobble of the star due to the gravitational interaction between the planet and the star, and the bigger the planet the more of an effect it’s going to have,” he said. “If you look at our solar system, the earth doesn’t affect the sun very much. It’s easier to detect a planet the size of Jupiter, which will have a bigger effect.”

Yet there is hope for the discovery of small planets using the star-wobble technique. Swiss astronomers found an exoplanet just four times the size of earth. And the 2013 telescope will be much more sensitive to smaller planets’ signatures.

The question many are dying to have answered is whether we’ll be able to detect life on another planet. According to Medin, we are very limited in what we can see from Earth.

“The problem is that it’s really hard to see anything other than the star,” said Medin. “The star really overwhelms everything around it. It would also be very difficult to fly to these planets. It would take thousands of years.”

Yet there may be other solutions for detecting extra-terrestrial life. Take Earth. Although our planet’s plants reflect a small amount of green light in the visible spectrum, they absorb almost all other visible light that hits them. However, plants do not absorb infrared light, which is not visible to the human eye. So anyone looking at Earth from a distant planet wouldn’t see green; they would see no reflected light at all in the visible spectrum, but with a special sensory would perceive a large amount of reflected infrared light. According to Dr. Robert E. Blankenship, a chemist at the University of Washington, such a jump of intensity, called the “red edge,” might be seen reflected from far-off exoplanets – but we’ll only catch it if we pay attention to the stars that shine on them.

“Photosynthesis has evolved to match the sun’s most intense output, which is the visible spectrum,” Blankenship said. “On another star, maybe a cooler star, you would have the curve shifted to longer wavelengths. Any photosynthetic organisms on a planet orbiting that star would have absorption spectra that take advantage of that distribution. A high red edge is a potential biosignature you might see.”


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