NASA’s in-space observatory, Kepler, has found 1,235 candidates for an alien planet. The observatory has been searching the cosmos for just over two years now; the $600 million mission launched March of 2009 and ever since has been monitoring the light coming from all stars in one patch of sky, looking for tiny flickers.

Essentially, when the light coming from a star flickers, it means that an exoplanet is orbiting it – it has briefly passed in between Kepler and the star, giving itself away as a candidate. Specifically, Kepler is searching for Earth-like worlds; this means that it keeps an eye on the planet for at least a year – it will only cross its sun once to make it on the list.

Once Kepler finds a likely star, the observation is confirmed by other telescopes. The mission has identified so many planetary candidates that astronomers now believe our Milky Way to host as many as 50 billion alien planets, with 2 billion of them approximately the size of our own.

Jason Rowe, an exceptionally ambitious member of the Kepler team, has put together a graphic to show us earthlings the scope of what the mission has found. A member of SETI (Search for ExtraTerrestrial Intelligence), Rowe told SPACE.com that:

The graphic itself has been great to show to people. There is lots of interesting astrophysics that one can present; my favorite one so far is that planets can be just as big as some of the smallest stars.

The graphic shows the parent stars in descending size, with their orbiting alien planets as the black dots. Our own Sun is the solo star in the second row, for size reference. The image is to scale, so we can see what Rowe meant – some black dots are as large as or even bigger than the smallest star in the bottom right. You can check out the full-sized image here.

Just 54 of these alien planets are orbiting their stars within what’s called the “Goldilocks Zone”, where the temperature is not too hot and not too cold – it’s just right for liquid water to exist on the planet’s surface. When extrapolated to the whole of the Milky Way, there could be as many as 500 million planets existing within a habitable zone.

The mission’s namesake, Kepler-11, is of the utmost interest – it looks remarkably like us. It harbors six low-mass planets composed of rocks and gas, probably with water, all orbiting one star. It also has the most confirmed orbiting planets.

NASA has a long list of alien planets to check up on in its future – Kepler has done the hard work of locating them, so now it’s up to astronomers to let us know if we have any neighbors.

Kepler’s home page has a counter which shows the number of confirmed planets.

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All images: NASA/Kepler, via SPACE.com