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Briefing Materials: Kepler Survey Catalog of Planet Candidates in the Cygnus Field

NASA will hold a media briefing at 11 a.m. EDT Monday, June 19, to announce the latest planet candidate results from the agency’s exoplanet-hunting Kepler mission. The briefing, taking place during the Kepler Science Conference, will be held at NASA’s Ames Research Center in California’s Silicon Valley.

The event will stream live on NASA’s website at:

The latest Kepler catalog of planet candidates was created using the most sophisticated analyses yet, yielding the most comprehensive and detailed accounting of distant worlds to date. This survey will enable new lines of research in exoplanet study, which looks at planets outside our solar system.

The briefing participants are:

  • Mario Perez, Kepler program scientist in the Astrophysics Division of NASA’s Science Mission Directorate in Washington
  • Susan Thompson, Kepler research scientist at the SETI Institute in Mountain View, California
  • Benjamin Fulton, doctoral candidate at the University of Hawaii at Manoa and the California Institute of Technology (Caltech) in Pasadena
  • Courtney Dressing, NASA Sagan Fellow at Caltech

NASA Media Advisory
NASA Press Release
Video – Press Conference
Audio – Press Conference
Short Video – NASA’s Kepler Reveals Potential New Worlds
Video News File – NASA’s Kepler Reveals Potential New Worlds

Scientific paper – Planetary Candidates Observed by Kepler. VIII. A Fully Automated Catalog with Measured Completeness and Reliability Based on Data Release 25 

Figure 1

Kepler measures the brightness of stars. The data will look like an EKG showing the heart beat. Whenever a planet passes in front of its parent star as viewed from the spacecraft, a tiny pulse or beat is produced. From the repeated beats we can detect and verify the existence of Earth-size planets and learn about the orbit and size of the planet.
Credits: NASA Ames and Dana Berry

Figure 2

Studying the Stars with Kepler
Kepler was the first NASA mission capable of detecting Earth-size planets, using the transit method, a photometric technique that measures the minuscule dimming of starlight as a planet passes in front of its host star. For the first four years of its primary mission, the space telescope observed a set starfield located in the constellation Cygnus (left). New results released from Kepler data today have implications for understanding the frequency of different types of planets in our galaxy and the way planets are formed. Since 2014 the Kepler telescope has been taking data on its extended second mission, observing fields on the plane of the ecliptic of our galaxy (right).
Credits: NASA/Ames Research Center/Wendy Stenzel
Studying the Stars with Kepler

Figure 3

Exoplanet Missions
This is an illustration of the different elements in NASA’s exoplanet program, including ground-based observatories, like the W. M. Keck Observatory, and space-based observatories, like Hubble, Spitzer, Kepler, TESS, James Webb Space Telescope, WFIRST and future missions.
Credits: NASA

Figure 4

New Kepler Planet Candidates
There are 4,034 planet candidates now known with the release of the eighth Kepler planet candidate catalog. Of these, 2,335 have been confirmed as planets. The blue dots show planet candidates from previous catalogs, while the yellow dots show new candidates from the eighth catalog. New planet candidates continue to be found at all periods and sizes due to continued improvement in detection techniques. Notably, 10 of these new candidates are near-Earth-size and at long orbital periods, where they have a chance of being rocky with liquid water on their surface.
Credits: NASA/Ames Research Center/Wendy Stenzel
New Kepler Planet Candidates

Figure 5

Discerning the Planet Candidates
In the final full survey of Kepler’s primary mission data, the entire data set was reprocessed using the mission’s most discerning analytical methods – a fully automated process represented here by the blue triangle. More than 4,000 planet candidates, including around 50 approximately the size of Earth and orbiting in the habitable zones of their stars, were identified in the data from observations of 200,000 stars. To be sure a lot of planets weren’t missed, the team introduced their own simulated planet transit signals into the data set and determined how many were correctly identified as planets. Then they added data that appear to come from a planet, but were really false signals, and checked how often the analysis mistook these for planet candidates. This process makes the eighth Kepler planet candidate catalog the best characterized set of high-confidence potential planets.
Credits: NASA/Ames Research Center/Wendy Stenzel

Figure 6

Kepler Habitable Zone Planets
Highlighted are new planet candidates from the eighth Kepler planet candidate catalog that are less than twice the size of Earth and orbit in the stars’ habitable zone – the range of distances from a star where liquid water could pool on the surface of an orbiting planet. The dark green area represents an optimistic estimate for the habitable zone, while the brighter green area represents a more conservative estimate for the habitable zone. The candidates are plotted as a function of their stars’ surface temperature on the vertical axis and by the amount of energy the planet candidate receives from its host star on the horizontal axis. Brighter yellow circles show new planet candidates in the eighth catalog, while pale yellow circles show planet candidates from previous catalogs. Blue circles represent candidates that have been confirmed as planets due to follow-up observations. The sizes of the colored disks indicate the sizes of these exoplanets relative to one another and to the image of Earth, Venus and Mars, placed on this diagram for reference. Note that the new candidates tend to be around stars more similar to the sun – around 5,800 Kelvin – representing progress in finding planets that are similar to the Earth in size and temperature that orbit sun-like stars.
Credits: NASA/Ames Research Center/Wendy Stenzel
Kepler Habitable Zone Planets

Figure 7

Studying Long Period Planets
NASA’s Kepler mission is unique in its ability to detect small planets orbiting relatively far from their stars, with relatively long orbital periods of more than 100 days. Kepler’s data will now allow researchers to study the planet populations making up this group (indicated by the green oval) which may include Earth-size planets located in the habitable zone around stars like our sun.
Credits: NASA/Ames Research Center/Wendy Stenzel

Figure 8

Small Planets are Common
This histogram shows the size distribution of planets discovered by NASA’s Kepler mission before the sizes were later refined with the help of the W. M. Keck Observatory. Smaller planets up to four times the size of Earth are more common than larger planets. The small planets originally appeared to span a range of sizes, but more precise size measurements from Keck revealed a scarcity of planets that are about 1.75 times the size of Earth.
Credits: NASA/Ames Research Center/CalTech/University of Hawaii/B.J. Fulton

Figure 9

Small Planets Come in Two Sizes
Researchers using data from the W. M. Keck Observatory and NASA’s Kepler mission have discovered a gap in the distribution of planet sizes, indicating that most planets discovered by Kepler so far fall into two distinct size classes: the rocky Earth-size and super-Earth-size (similar to Kepler-452b), and the mini-Neptune-size (similar to Kepler-22b). This histogram shows the number of planets per 100 stars as a function of planet size relative to Earth.
Credits: NASA/Ames Research Center/CalTech/University of Hawaii/B.J. Fulton

Figure 10

New Branch in the Exoplanet Family Tree
This sketch illustrates a family tree of exoplanets. Planets are born out of swirling disks of gas and dust called protoplanetary disks. The disks give rise to giant planets like Jupiter as well as smaller planets mostly between the size of Earth and Neptune. Researchers using data from the W. M. Keck Observatory and NASA’s Kepler mission discovered that these smaller planets can be cleanly divided into two size groups: the rocky Earth-like planets and super-Earths, and the gaseous mini-Neptunes.
Credits: NASA/Ames Research Center/JPL-Caltech/Tim Pyle
New Branch in Exoplanet Family Tree

Figure 11

Assembly Line of Planets
This diagram illustrates how planets are assembled and sorted into two distinct size classes. First, the rocky cores of planets are formed from smaller pieces. Then, the gravity of the planets attracts hydrogen and helium gas. Finally, the planets are “baked” by the starlight and lose some gas. At a certain mass threshold, planets retain the gas and become gaseous mini-Neptunes; below this threshold, the planets lose all their gas, becoming rocky super-Earths.
Credits: NASA/Ames Research Center/JPL-Caltech/R. Hurt
Assembly Line of Planets

Figure 12

Exoplanet Populations
The population of exoplanets detected by the Kepler mission (yellow dots) compared to those detected by other surveys using various methods: radial velocity (light blue dots), transit (pink dots), imaging (green dots), microlensing (dark blue dots), and pulsar timing (red dots). For reference, the horizontal lines mark the sizes of Jupiter, Neptune and Earth, all of which are displayed on the right side of the diagram. The colored ovals denote different types of planets: hot Jupiters (pink), cold gas giants (purple), ocean worlds and ice giants (blue), rocky planets (yellow), and lava worlds (green). The shaded gray triangle at the lower right marks the exoplanet frontier that will be explored by future exoplanet surveys. Kepler has discovered a remarkable quantity of exoplanets and significantly advanced the edge of the frontier.
Credits: NASA/Ames Research Center/Natalie Batalha/Wendy Stenzel
Exoplanet Populations