While the number of confirmed extrasolar planets is now approaching 300, the tally of extrasolar moons so far identified is still a rather disappointing zero. Planets beyond our solar system are incredibly challenging to find. Moons are nearly impossible with today's technology, given that they are generally expected to be quite small compared to their parent worlds. Even Earth's moon is invisible on the famous "pale blue dot" image obtained by Voyager 1 from the comparatively small distance of 3.7 billion miles — a photograph taken from well within our solar system. But the search is not impossible, says Darren Williams, associate professor of physics and astronomy at Penn State Erie, the Behrend College. Williams believes a moon in orbit around a known extrasolar planet will also be detectable if we look hard enough with the right techniques. "It will add a periodic component to the combined infrared signal" of the planet-moon system, he said. Finding moons is more than just an academic quest to count them up. Planetary satellites can be highly interesting in their own right. It's possible, for example, that life could exist on extrasolar moons, researchers say. And it has been suggested that the ocean tides induced by Earth's moon may have been necessary to create the conditions for life on our planet to begin.

At the least, the evolution of life has been affected by our moon's constant tugging. "We certainly owe our present climate stability to the Moon and its stabilizing influence on the spin axis, but I'm not convinced that big moons are a requirement for simple or advanced life," Williams said. "I do think that Earth would have evolved advance life even with greater seasonal extremes, but it may have taken a different evolutionary path."

View: Full Article | Source: Space.com