Astro 101 Slide Set: Keplers Exoplanet Discoveries Exceed 1,000
0 Topic: Exoplanets Concepts: Transit Detection, Exoplanet
Statistics Mission: Kepler Coordinated by: the NASA Astrophysics
Forum An Instructors Guide for using the slide sets is available at
the ASP website https://www.astrosociety.org/e
ducation/resources-for-the- higher-education-audience/
https://www.astrosociety.org/e ducation/resources-for-the-
higher-education-audience/ Developed by: the Kepler Team DRAFT
6/15
Slide 2
The Discoveries In January 2015, the Kepler team, analyzing
data gathered by the Kepler spacecraft during its four-year primary
mission (2009-2013), announced its 1,000 th verified extrasolar
planet (exoplanet) discoveryincluding three more that are both less
than two Earth diameters in size, and orbit within the habitable
zone of their parent stars (i.e., the regions where the temperature
range could allow for liquid water on planetary surfaces)bringing
the current total of these to eight. The team also added 500+
candidates to the roll of 3,000+ potential planets yet to be
verified, including six of near- Earth size orbiting in the
habitable zones of Sun-like stars. 1 Three of the eight verified
near-Earth-size planets orbiting in habitable zones are among the
newly-validated. Two of these Kepler-438b and Kepler-442b--are less
than 1.5 times the diameter of Earth and are likely made of rock.
They orbit stars smaller and cooler than the sun, 475 and 1,100
light years away, respectively. Credit: NASA Ames/Kepler Mission/W.
Stenzel.
Slide 3
How Are the Discoveries Made? Kepler detects planets by taking
a photometric measurement of the stars in its field of view every
30 minutes. A planet transit will show as a small periodic dip in
the light curve of a star over time. If the host stars diameter and
temperature are known, then from the simple dip in the the light
curve Kepler can determine the planets diameter and orbital period;
the planets surface temperature can also be estimated. Kepler
cannot independently determine the planets mass or composition, nor
its atmospheric composition. 2 The animation shows how Kepler
detects planets. As the planet passes between the host star and the
spacecraft, the observed star brightness decreases slightly,
signaling the potential detection of a planet. Kepler looked at
over 150,000 stars continuously for four years in the
constellations Cygnus and Lyra, seeking to record the slight
periodic brightness changes in stars that could reveal the presence
of planets. Credit: NASA Ames/Kepler Mission/SETI Institute/D.
Berry. Kepler field of view. Credit: NASA Ames/Kepler Mission/C.
Roberts and W. Stenzel.
Slide 4
The Big Picture 3 Prior to Kepler, the vast majority of known
exoplanets were Neptune-size or larger. This was a selection bias
due to the difficulty of detecting smaller exoplanets. Kepler can
detect, and is detecting, smaller planets not possible by other
methods, and is increasing the odds of finding planets that
resemble Earth. An important goal in the search for exoplanets is
to find that other Earthone of similar size, orbiting in the
habitable zone of a sun-like star, possessing an Earth-like
atmosphere, possibly harboring life as we know it. Artists
conception of Kepler-186f. Credit: NASA Ames/SETI
Institute/Caltech. Keplers 1,000 exoplanet discoveries and
countinghave demonstrated that planets are everywhere, and that
small planets are more common than large ones.
Slide 5
What are the Implications? Kepler has shown that small planets
are more plentiful than larger, Jupiter- sized worlds, and are
abundant in our galaxy. Current models show that planets with a
diameter smaller than roughly 1.5 times that of Earth are more
likely to have rocky surfaces that could support liquid water and
appropriate conditions to foster life as we know it. Earth-size
planets are therefore key to discovering life beyond our solar
system. As Kepler finds more exoplanets, that ultimate goal comes
closer! 4 Credit: NASA Ames/Kepler Mission/W. Stenzel.
Slide 6
Resources 5 The Kepler Misson Websites o http://kepler.nasa.gov
http://kepler.nasa.gov o http://www.nasa.gov/Kepler
http://www.nasa.gov/Kepler Scientific Paper o Kepler Planet Catalog
Paper, Planetary Candidates Observed by Kepler VI: Planet Sample
from Q1-Q16 (47 Months) http://arxiv.org/abs/1502.02038
http://arxiv.org/abs/1502.02038 Additional Resources o Exoplanet
Resource guide http://www.astrosociety.org/education/astro
nomy-resource-guides/the-search-for- planets-around-other-stars/
http://www.astrosociety.org/education/astro
nomy-resource-guides/the-search-for- planets-around-other-stars/ o
Online Exoplanet database http://exoplanets.org
http://exoplanets.org o The online Kepler data Repository
https://archive.stsci.edu/kepler/ https://archive.stsci.edu/kepler/
NASA Exoplanet Archive: o http://exoplanetarchive.ipac.caltech.edu/
http://exoplanetarchive.ipac.caltech.edu/ Image Credit: NASA
Ames/Kepler Mission/W. Stenzel.
Slide 7
Exoplanet Discoveries 6 Animation Credit: NASA Ames/Kepler
Mission/N. Batalha
Slide 8
Exoplanets Plotted 7 This figure plots exoplanet discoveries on
a graph showing the size (radius) versus the orbital period. Kepler
transit discoveries are shown as yellow dots. The pink dots
represent transit discoveries by other means than Kepler. The light
blue dots represent discoveries using the radial velocity method
(measuring the toward-and-away wobbles of stars induced by the
gravitational tugs of orbiting planets). The other colors account
for direct imaging and other methods. Image credit: NASA
Ames/Kepler Mission/N. Batalha.
Slide 9
Planets in Habitable Zones This figure shows both currently
confirmed and candidate exoplanets orbiting in the habitable zone
of their respective stars. Their positions on the graph are
determined according to the surface temperature of their parent
star versus the energy received by the planet. The green bands
represent the habitable zonethe region in which water on a rocky
surface could exist in liquid form under the right conditions. The
graph shows Venus, Earth and Mars for reference. Recently confirmed
planets are labeled. 8 Image credit: NASA Ames/Kepler Mission/N.
Batalha/W. Stenzel.