Kepler Discovers Over a Thousand New Planets
published during a waxing crescent moon.
05/10/2016

Thousand New Planets

Kepler’s candidates require verification to determine if they are actual planets and not another object, such as a small star, mimicking a planet. Credit: NASA

If you could live anywhere, which planet would you choose? NASA might have found an additional 1,284 to choose from – only about 11 light-years away, according to Natalie Batalha, Kepler mission scientist at NASA’s Ames Research Center in Moffett Field, Cal. That brings the current candidate pool to 2,268 with another 1,327 more possible. It might sound exciting, but don’t pull out the moving boxes just yet.

Today NASA announced this discovery in conjunction with a paper published in the Astrophysical Journal describing the latest results of the Kepler Mission to find earth-like, habitable planets in our galaxy. For over four years, the Kepler spacecraft looked at and surveyed 150,000 stars in one part of the Milky Way with the goal of finding a specific kind of planet. Called exoplanets, these are planets similar to earth. They orbit a star in what NASA dubbed the “Goldilocks Zone.” This is the region with conditions that are “just right” for liquid water on a planet’s surface. In other words, it could support life, human and otherwise.

For every planet that passed in front of a star (meaning it’s lit from behind), Kepler took numerous measurements. The planet had to meet certain criteria to be considered viable, and then the data was sent to earth – massive amounts of it. Scientists had to find a way to look through all of that to find out if there are any such exoplanets. If yes, which ones could be Goldilocks planets and therefore worth exploring further?

Thousand New Planets

A new statistical validation technique enables researchers to quantify the probability that any given candidate signal is in fact caused by a planet, without requiring any follow-up observations. This technique uses two different kinds of simulations– both simulations of the detailed shapes of transit signals caused by both planets and objects, such as a star, masquerading as planets (left diagram), and also simulations of how common imposters are expected to be in the Milky Way galaxy (right diagram). Combining these two different kinds of information gives scientists a reliability score between zero and one for each candidate. Candidates with reliability greater than 99 percent are call “validated planets.” Credits: NASA Ames/W. Stenzel; Princeton University/T. Morton

Before Kepler, scientists identified exoplanets using ground-based telescopes and an “in-depth study on a case-by-case basis,” said Tim Morton, associate research scholar at Princeton University in New Jersey. This “time and resources intensive” approach means about 200 of these planets were confirmed in 15 years. By contrast, Kepler found 4,302 candidates – unconfirmed exoplanets – in a fraction of that time. Information about them gives a whole new meaning to the term “big data.”

To differentiate between exoplanets and an “astrophysical false positive,” or stars that masquerade as planets, Morton developed a new method of analysis. The technique combines known data about the galaxy, data about those false positives and Kepler planet reading to find the right kind of planet. The results are far more accurate than ground-based analysis; 60-70 percent of those candidates were false.

Batalha says that this data makes it possible to better extrapolate from this one sample just how many planets there are in the galaxy.

“Now the task at hand is to transform that discovery…into the actual population of planets in the galaxy,” said Batalha. “It’s hoped that astronomers around the world will point their telescopes at these systems to better understand the properties of the host stars and the planets themselves.”

Thousand New Planets

Since Kepler launched in 2009, 21 planets less than twice the size of Earth have been discovered in the habitable zones of their stars. The orange spheres represent the nine newly validated planets announcement on May 10, 2016. The blue disks represent the 12 previous known planets. These planets are plotted relative to the temperature of their star and with respect to the amount of energy received from their star in their orbit in Earth units. The sizes of the exoplanets indicate the sizes relative to one another. The images of Earth, Venus and Mars are placed on this diagram for reference. The light and dark green shaded regions indicate the conservative and optimistic habitable zone. Credits: NASA Ames/N. Batalha and W. Stenzel

The Kepler mission is now in its “close-out phase” and will publish the final discovery catalogue of planetsby October 2017. The team is also compiling a comprehensive database of findings that will be available for astronomers and scientists of future missions to add even more information. To that end, NASA will launch TESS in 2017, and the European Space Agency mission Plato will launch around 2020.

These discoveries provide a new perspective on our universe, according to Batalha.

“We’re going to change the way you see the universe,” she said. “When you look up in the sky, you’re not just going to see pinpoints of light and see them as stars… You’re going to see them as planetary systems.

“It’s part of that larger goal of finding evidence of life beyond earth. To know if we’re alone or not. To know…how life manifests itself in the galaxy and what is the diversity.”