An additional 1,284 objects spotted by NASA’s planet-hunting spacecraft Kepler are confirmed planets, agency astronomers said today. That brings the total number of verified exoplanets from Kepler to more than 2,000 — more than doubling the amount spotted by the spacecraft. "We have more than doubled the number of known exoplanets smaller than the size of Neptune," said Tim Morton, an associate research scholar at Princeton University.
"We have more than doubled the number of known exoplanets smaller than the size of Neptune."
This is the largest amount of exoplanets (or planets outside our Solar System) ever confirmed at the same time. The same research group also found that 707 of the objects spotted by Kepler probably weren't exoplanets, according to a study published in The Astrophysical Journal. The findings help scientists focus their efforts as they attempt to explore how common Earth-like planets are in the Universe, and which ones could possibly support life.
During its time in space, Kepler has located more than 4,500 possible exoplanet "candidates," but scientists have only confirmed some of these to be exoplanets. Kepler hunts for exoplanets by observing the brightness of stars throughout the galaxy. When an orbiting planet passes in front of its host star — what's known as a transit — it causes a slight dip in the star's luminosity that Kepler can measure. These "transit signals" can be used to calculate the size, orbital period, and mass of a far away exoplanet.
But sometimes, a transit signal can be a false positive — caused by something other than an orbiting world. To be certain of what Kepler has found, researchers most go through a process of validating the signals from the spacecraft to determine which ones are most likely caused by exoplanets. That process requires doing in-depth study of each possible candidate, typically on a case-by-case basis. But thanks to new mathematical models developed by Morton, NASA was able to determine the likelihood of Kepler candidates being exoplanets on a much larger scale.
An artist rendering of NASA's Kepler spacecraft. (NASA)
Thanks to the efforts of Kepler and other telescopes, more than 5,000 exoplanet candidates have been identified so far. Today’s announcement brings the total number of confirmed exoplanets to more than 3,200 — most of those coming from Kepler data.
Of today’s batch of confirmed exoplanets, more than 550 could be rocky based on how big they are, according to NASA. Plus, nine of those planets are thought to orbit in the habitable zone — the right distance away from a star where water can pool on a planet’s surface. Since Earth is also a rocky planet that orbits in a habitable zone, these nine exoplanets could be prime targets in the continuing search for alien life.
Astronomers estimate there are around 10 billion rocky planets in our galaxy orbiting in a habitable zone
So far, only 21 rocky, potentially habitable planets have been confirmed from Kepler’s findings. But based on the spacecraft’s data, astronomers estimate there are around 10 billion rocky planets in our galaxy orbiting in a habitable zone, according to Natalie Batalha, a Kepler mission scientist at NASA's Ames Research Center.
NASA hopes to study the atmospheres of these Kepler exoplanets soon. In 2018, the agency will launch its James Webb Space Telescope, which will be the most powerful space telescope ever built. James Webb will potentially be able to study these exoplanets in greater detail, by measuring how starlight filters through these planets’ atmospheres. How light passes through an atmosphere can indicate the types of gases that are present, suggesting whether or not biological life can be found on the planet’s surface.