If you've ever wondered if we are "alone", new research may put that question to rest. Probes are searching for hundreds of worlds the size of Earth that move in Earth-like orbits around sun-like stars. Astronomers expect to have exciting new answers within the next three years.

The most advanced planet-hunting probes in existence are the European Space Agency’s COROT satellite and NASA's Kepler spacecraft. These probes are designed to spot close-in planets easily.

For hundreds of years, astronomers have sought answers to questions such as “are planets like Earth so rare that we're essentially marooned in the universe, or are they so common that life could find many other homes beyond the solar system?” David Latham is the mission’s co-investigator from the Harvard-Smithsonian Center for Astrophysics. As he tells msnbc.com, "The biggest impact has to be, to support the idea that we aren't alone, in the sense that there are other planets out there rather like the Earth." Latham concludes, "We're confident that they're out there, but we don't have any (proof) yet."

Scientists aren’t expecting to necessarily find a carbon copy of Earth. A planet doesn’t have to revolve around a sun-like star to be hospitable for life. As Latham points out, "The excitement, at least in the scientific community, is the possibility that there will be super-Earths that might be even better for the evolution of life in the universe."

We should expect to hear about the weirdest planets first. According to sources, the first planets may be “hot Jupiters" whirling so close to their stars that they sizzle. Planets in the range of two to 10 times the Earth’s mass are called "super-Earths." Apparently, these kinds of worlds are prime targets for Kepler and COROT.

William Borucki is a scientist at NASA's Ames Research Center and Kepler's principal investigator. He expects his science team will present about 30 papers on this subject at next month's American Astronomical Society meeting in Washington. Further, Borucki told msnbc.com that the results being turned up by Kepler are so unusual that the team may not immediately go public with them.

And just how are these planets reviewed? For one, the two probes stare at stars, one by one, and measure the slight dip in their brightness as planets periodically pass over the stars' disks. They also detect planets, not by tracking radial velocity but by checking planetary transits. Kepler is scheduled to check 150,000 stars during its three-and-a-half year mission. It's hoped that these checks will indicate how common alien Earths are in a representative sample of the universe. In addition to the probe’s research, the Kepler team is working with astronomers at ground-based telescopes.

But what if there are no other Earth-like planets? As Borucki tells it, "A dry hole would be a very, very interesting result … You will have dramatically affected mankind's future. There'd be no Star Trek in that case, no place to go." Either way, astronomers should know the answer by 2013.

Space probes may soon prove that other Earth-like planets exist
Two space probes scan the universe for signs of planets that could support life. Scientists hope to have answers in less than 3 years.