The $591 million Kepler mission launched successfully last night, and will soon begin looking for Earth-like planets in other solar systems.

The Delta II rocket carrying the Kepler planet-hunting spacecraft lifted off on time at 10:49 p.m. EST from Launch Complex 17-B at Cape Canaveral Air Force Station in Florida. The spectacular nighttime launch followed a smooth countdown free of technical issues or weather concerns.

Kepler’s mission: to peer closely at a patch of space for at least three-and-a-half years, looking for rocky planets similar our own. The spacecraft will target an area rich with stars like our sun, watching for a slight dimming in the starlight as planets slip through the space between.

Image credit: NASA/Jack Pfaller

Some facts about the mission, from the NASA website:

* Kepler is the world’s first mission with the ability to find true Earth analogs — planets that orbit stars like our sun in the “habitable zone.” The habitable zone is the region around a star where the temperature is just right for water — an essential ingredient for life as we know it — to pool on a planet’s surface.

* By the end of Kepler’s three-and-one-half-year mission, it will give us a good idea of how common or rare other Earths are in our Milky Way galaxy. This will be an important step in answering the age-old question: Are we alone?

* Kepler detects planets by looking for periodic dips in the brightness of stars. Some planets pass in front of their stars as seen from our point of view on Earth; when they do, they cause their stars to dim slightly, an event Kepler can see.

* Kepler has the largest camera ever launched into space, a 95-megapixel array of charge-coupled devices, or CCDs, like those in everyday digital cameras.

* Kepler’s telescope is so powerful that, from its view up in space, it could detect one person in a small town turning off a porch light at night.