NASA scientists announced 1,284 new exoplanets at a news conference Tuesday — candidates found by the Kepler Space Telescope that have now been confirmed with 99 percent certainty. It more than doubles the count of confirmed planets for the space telescope.

On Monday, Mercury passed between Earth and the sun — with all three celestial bodies lining up for Mercury to appear as a small black dot creeping over the sun. That phenomenon — one planet passing in front of its star, from the visual perspective of another planet — is known as a “transit.”

And that's how Kepler finds new worlds. It's our best method for detecting exoplanets.

Scientists are working on parsing out the mission's data. They have to weed out false positives from the thousands of potential planets — star dimming caused by companion stars or other objects.

In a paper published Tuesday in the Astrophysical Journal, a team led by Princeton University's Timothy Morton presents a new statistical method for calculating the likelihood that a given candidate is a planet. Their analysis yielded 1,284 confirmations.

Another 1,327 planets from the Kepler catalog are almost certainly planets, according to the researchers, but these worlds don't reach the 99 percent probability threshold, so more study will be needed to confirm their existence.

The other 707 potential worlds are likely nonexistent, according to the analysis.

As of today, NASA knows of 21 exoplanets that it considers likely to be rocky, potentially wet worlds.

Based on Kepler data, our galaxy probably has more than 10 billion rocky planets that live in the habitable zones of their stars, said Kepler mission scientist Natalie Batalha.