Exoplanet- a planet that orbits another star

The blocky space telescope was still getting its bearings, just a few months after launch, when the floodgates burst open.

As NASA's Kepler Space Telescope science team was wrapping up a 10-day trial run, they saw something that bordered on the unbelievable: the telescope's first detection of a rocky, Earth-sized world outside our solar system.

The planet, a hot, heavy world dubbed Kepler 10b, would be among the early nuggets in a coming gold rush of exoplanet discovery-taking us from a handful of planets confirmed to be in orbit around other stars to more than 3,300 today, all in the space of two decades. Thousands more candidate planets found by Kepler await confirmation.

"In that trial run we saw, already, the signal of what could be a small planet orbiting a star about 540 light years away," Natalie Batalha, an astrophysicist and member of the Kepler team, told a public radio host about the discovery, announced in 2011. "This was our first indication-'Oh my god! We're going to find lots of these things. We're going to find lots of Earth-size planets.'"

Since the first confirmation of an exoplanet orbiting a sun-like star in 1995, and with only a few, narrow slices of our Milky Way galaxy so far surveyed, we've already struck many rich veins. A recent statistical estimate places, on average, at least one planet around every star in the galaxy. That means there's something on the order of a trillion planets in our galaxy alone, many of them in Earth's size range.

"Right now we know, for the first time, that small planets are very common," said Sara Seager, a professor at the Massachusetts Institute of Technology and an exoplanet research pioneer. "It's phenomenal. We had no way to know that before Kepler. We'll just say, colloquially: They're everywhere."

Hey exoplanets: Say 'cheese!'

Astronomers say the future of exoplanet exploration is all about direct observation. Missions like the James Webb Space Telescope, now under construction, and the planned WFIRST (Wide-Field Infrared Survey Telescope) will expand and sharpen our ability to capture actual images of distant planets.

New technology under development will boost these capabilities, allowing us to snap portraits of smaller and smaller exoplanets. The WFIRST mission, for example, will use an internal instrument called a coronagraph to selectively block and process incoming starlight to reveal the planets hidden in the glare.

Something similar could be done outside the telescope by a device called the starshade, being developed at JPL. The starshade would deploy in deep space like a sunflower the size of a baseball diamond. Tens of thousands of miles away, a space telescope would point toward it; the starshade would block unwanted starlight, allowing the space telescope to capture images of the planets around the target star.

In coming decades, as space telescopes grow larger and more refined, perhaps we'll finally capture the iconic image of another Earth-a faraway world of continents, clouds and oceans.

Information Taken from: https://exoplanets.nasa.gov/the-search-for-life/exoplanets-101/