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Scientists say they have detected the nearest planet outside of our solar system, an alien world about the size of Earth that's orbiting a star called Alpha Centauri B.

Imaginary planets in the Alpha Centauri star system have been a staple of science fiction for decades. That's because the three stars in this system—Alpha Centauri A, B, and C—are only about four light years from our Sun. That's far away, but it's still closer than everything else beyond our solar system, so Alpha Centauri has long been a tempting destination for storytellers who dream of interstellar travel.

Here's your chance to weigh in on mutant forms of bird flu that have been in the news — the U.S. government wants to know just how scary you think these new viruses are.

Two Americans have won the 2012 Nobel Prize in Chemistry. Robert Lefkowitz and Brian Koblika were awarded the prize for their work on protein receptors that tell cells what's going on around the human body. Their research has allowed drug makers to develop medication with fewer side effects. The pair with share the $1.2 million award.

Americans Robert Lefkowitz and Brian Kobilka have won the 2012 Nobel Prize in chemistry. The Royal Swedish Academy of Sciences cited the two researchers Wednesday "for studies of G-protein-coupled receptors."

What was supposed to be a 60-day moratorium on certain experiments involving lab-altered bird flu has now lasted more than eight months. And there's no clear end in sight.

Researchers still disagree on how to best manage the risks posed by mutant forms of highly pathogenic H5N1 bird flu. The altered viruses are contagious between ferrets, which are the lab stand-in for humans. The fear is that these germs could potentially cause a deadly flu pandemic in people if they ever escaped the lab.

A long, controversial investigation of a polar bear scientist has ended with his government employer saying it does not look like he engaged in any scientific misconduct.

Charles Monnett is a wildlife researcher with the Bureau of Ocean Energy Management, part of the Department of the Interior. He and a colleague, Jeffrey Gleason, wrote an influential 2006 report describing apparently drowned polar bears floating in the Arctic, which they saw during a routine aerial survey of whales.

NASA's newest Mars rover, Curiosity, has snapped photos of rocky outcroppings that jut out from the alien soil, and scientists say they look like the remnants of an ancient stream bed where water once flowed on the surface of the red planet.

The exposed rocks look like broken slabs of concrete sidewalk, about four inches thick, and are made of rounded bits of gravel in a sandy matrix. The rock has eroded a little bit, and some of the smooth pebbles — about the size of M&M candies — have fallen down into a little pile.

Scientists have discovered that a mouse found in Africa can lose large patches of skin and then grow it back without scarring, perhaps as a way of escaping the clutches of a predator.

The finding challenges the conventional view that mammals have an extremely limited ability to replace injured body parts. There are lizards that can regrow lost tails, salamanders that can replace amputated legs, and fish that can generate new fins, but humans and other mammals generally patch up wounds with scar tissue.

One hundred ten chimpanzees will retire from biomedical research, the National Institutes of Health announced today. The move comes as some groups are pushing for a ban on all medical chimp research.

The NIH has been reviewing its chimp research since December. That's when a report from the Institute of Medicine said that there was almost no scientific need for doing biomedical research on chimps.

Space shuttle Endeavour begins a kind of farewell tour this week. The shuttle will set off on a cross-country trip to its retirement home, flying from Florida to Los Angeles on the back of a modified jumbo jet.

Along the way, the spaceship will stop off in Houston, home of NASA's Mission Control and, weather permitting, fly over NASA centers and various landmarks in cities that include San Francisco and Sacramento.