[skipwords]NASA has been on a roll lately, despite some prominent criticism over the past year. The shuttle era may be over, but NASA still has about 100 active missions on its plate, from science satellites and lunar probes to Mars rovers and deep-space telescopes. Its Kepler telescope, for example, just discovered 41 new alien planets in one fell swoop, raising its total to more than 2,300 suspected planets outside our solar system.

To put that number in perspective, planetary scientist Alex Parker made the following animation of Kepler's top 2,299 planet candidates, all shown together as if they orbited a single star. Each one is drawn to scale, Parker notes on Vimeo, with an accurate radius, orbital period and orbital distance:

Parker, who works at the Harvard-Smithsonian Center for Astrophysics, says he made the video to help people grasp the enormity of Kepler's discoveries. "I wanted to convey the astounding number of planet candidates Kepler has found in a way that would really impact the person watching this video," he says in a statement. Scientists call these "candidates" because some will turn out to be false positives, but most are expected to eventually be confirmed as planets.

The video puts all these worlds in one solar system to show their quantity and diversity, but in reality they orbit 1,770 stars, some of which host multiple planets. They range in size from one-third to 84 times Earth's diameter, and Parker color-coded them based on estimated temperatures — from the bluest, coldest at -166 degrees Fahrenheit (-110 Celsius) to the reddest, hottest at 8,286 F (4,586 C).

NASA launched Kepler in March 2009, placing it in Earth-trailing orbit around the sun so our planet doesn't block its view of others. Since then, the one-ton spacecraft has found 2,321 planet candidates amid more than 100,000 stars, which it surveys by looking for the telltale twinkle of a passing planet. Such planetary "transits" are rare and brief, but Kepler watches so many stars that it sees them all the time.

The study of extrasolar planets, or exoplanets, is still relatively new, as scientists only began confirming their existence in the last 25 years. It's unknown how many are out there, but one 2011 study suggested "50 percent of solar-type stars harbor at least one planet," and another estimated the Milky Way alone contains at least 160 million. Most of the exoplanets found so far are huge and close to their stars, as seen in Parker's video: The three white rings represent the average orbital distances of Mercury, Venus and Earth on the same scale. Still, Kepler has found at least some hints of "potentially habitable" planets beyond our own.

Kepler's funding was originally scheduled to run out this November, but NASA recently announced it will extend it through at least fiscal year 2016. "The Kepler mission is an outstanding success," a NASA committee wrote in an April report recommending the extension. "Kepler is not only a unique source of exoplanet discoveries, but also an organizing and rallying point for exoplanet research."[/skipwords]

[Via Smithsonian Science]

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