About 800 planets have been confirmed to exist outside our solar system, in addition to nearly 2,000 planet candidates found with the Kepler mission.
7. Vesta becomes a 'protoplanet'
NASA's Dawn spacecraft helped scientists to determine that Vesta, originally thought of as an asteroid, is a "protoplanet." That means that its structure has a dense, layered body, and it orbits the sun.
What's the difference between a protoplanet and a planet? It appears that something interrupted the development of protoplanets, which aren't fully formed, so they don't quite make the cut as full-fledged planets.
8. Bye-bye, space shuttles
In 2011, we said goodbye to NASA's Space Shuttle Program. This year, we saw the four surviving orbiters making Earthly journeys -- whether flown or towed -- to new homes at museums and similar attractions.
Discovery is at the Udvar-Hazy Center at the Smithsonian Institution's National Air and Space Museum in Chantilly, Virginia. It flew on the back of a 747 from Kennedy Space Center. This is the most traveled of the space shuttles.
Enterprise is at the Intrepid Sea-Air-Space Museum in New York. This shuttle never actually went into space, but it was carried on a 747 jet from Washington to New York in June. It was originally designed as a prototype test vehicle.
Endeavour is at the California Science Center in Los Angeles, having flown from Kennedy Space Center on the back of a 747. To make room for it to be towed through the city, dozens of trees were cut down and traffic signs removed.
Atlantis is at the Kennedy Space Center in Merritt Island, Florida. It was the last space shuttle to go to space, and the last to come to rest this year. Unlike the other shuttles, which made flyovers in various parts of the United States, Atlantis moved only 10 miles, towed by land to the Kennedy Space Center Visitor Complex in November.
The other two shuttles -- Challenger and Columbia -- did not make it back to Earth after accidents that killed their entire crews.
9. SpaceX gets to the space station, and back
No NASA shuttles flew in 2012, but a private company called SpaceX successfully sent almost 900 pounds of cargo to the international space station in its first official mission in October. The Dragon capsule came back with nearly 1,700 pounds of freight. This was only months after the SpaceX demonstration flight in May.
NASA and SpaceX have a contract for a dozen flights to the space station, and the October trip was just the first.
SpaceX isn't the only player in this commercial spaceflight arena. Virgin Galactic, Sir Richard Branson's private spaceflight company, recently completed a high-altitude test. Orbital Sciences is also under contract with NASA, and will also launch a demonstration flight.
10. Baby's DNA constructed before birth
For the first time, researchers at the University of Washington were able to construct a near-total genome sequence of a fetus, using a blood sample from the mother and saliva from the father.
The study suggested this method could be used to detect thousands of genetic diseases in children while they are still in the fetal stage. In the long run, it could help scientists derive new insights about genetic diseases.
Right now, this sequencing costs in the neighborhood of $50,000, but given how rapidly the price of genetic testing is falling, the process may become less expensive over time. Of course, it also raises ethical issues about selecting certain desirable traits in children. For right now, however, the technology is still in its early stages.
What were your favorite science stories this year? Share them in the comments.