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vey Instrument (DSSI) on the Gemini North telescope. DSSI is a visiting instrument
developed by a team led by Howell who adds, ¡°DSSI on Gemini Rocks! With this com-
bination, we can probe down into this star system to a distance of about 4 times that
between the Earth and the Sun. It¡¯s simply remarkable that we can look inside other
solar systems.¡± DSSI works on a principle that utilizes multiple short exposures of an
object to capture and remove the noise introduced by atmospheric turbulence produc-
ing images with extreme detail.
Observations with the W.M. Keck Observatory used the Natural Guide Star Adaptive
Optics system with the NIRC2 camera on the Keck II telescope. NIRC2 (the Near-
Infrared Camera, second generation) works in combination with the Keck II adaptive
optics system to obtain very sharp images at near-infrared wavelengths, achieving
spatial resolutions comparable to or better than those achieved by the Hubble Space
Telescope at optical wavelengths.
¡°The observations from Keck and Gemini, combined with other data and numerical
calculations, allowed us to be 99.98% confident that Kepler-186f is real,¡± says Thomas
Barclay, a Kepler scientist and co-author on the paper. (source: www.gemini.edu)
Star System Probe Discovers Kepler-186f
First validated Earth-size planet found in a possible habitable zone
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First Potentially Habitable Earth-Sized Planet
Confirmed By Gemini And Keck Observatories
The discovery of the first Earth-sized exoplanet orbit-
ing within the habitable zone of another star has been
confirmed by observations with both the W. M. Keck
Observatory and the Gemini Observatory. The initial
discovery, made by NASA¡¯s Kepler Space Telescope,
is one of a handful of smaller planets found by Kepler
and verified using large ground-based telescopes.
¡°What makes this finding particularly compelling is
that this Earth-sized planet, one of five orbiting this
star, which is cooler than the Sun, resides in a temper-
ate region where water could exist in liquid form,¡±
says Elisa Quintana of the SETI Institute and NASA
Ames Research Center who led the paper published
in the current issue of the journal Science. The region
in which this planet orbits its star is called the habit-
able zone, as it is thought that life would most likely
form on planets with liquid water.
Steve Howell, Kepler¡¯s Project Scientist and a co-
author on the paper, adds that neither Kepler (nor
any telescope) is currently able to directly spot an
exoplanet of this size and proximity to its host star.
¡°However, what we can do is eliminate essentially all
other possibilities so that the validity of these planets
is really the only viable option.¡±
With such a small host star, the team employed a
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technique that eliminated the possibility that either a background star or a stellar
companion could be mimicking what Kepler detected. To do this, the team obtained
extremely high spatial resolution observations from the eight-meter Gemini North
telescope on Mauna Kea in Hawaii using a technique called speckle imaging, as well
as adaptive optics(AO) observations from the ten-meter Keck II telescope, Gemini¡¯s
neighbor on Mauna Kea. Together, these data allowed the team to rule out sources
close enough to the star¡¯s line-of-sight to confound the Kepler evidence, and conclude
that Kepler¡¯s detected signal has to be from a small planet transiting its host star.
¡°The Keck and Gemini data are two key pieces of this puzzle,¡± says Quintana. ¡°With-
out these complementary observations we wouldn¡¯t have been able to confirm this
Earth-sized planet.¡±
The Gemini ¡°speckle¡± data directly imaged the system to within about 400 million
miles (about 4 AU, approximately equal to the orbit of Jupiter in our solar system)
of the host star and confirmed that there were no other stellar size objects orbiting
within this radius from the star. Augmenting this, the Keck AO observations probed a
larger region around the star but to fainter limits. According to Quintana, ¡°These
Earth-sized planets are extremely hard to detect and
confirm, and now that we¡¯ve found one, we want to
search for more. Gemini and Keck will no doubt play a
large role in these endeavors.¡±
The host star, Kepler-186, an M1-type dwarf star, is
very dim, being over half a million times fainter than
the faintest stars we can see with the naked eye.
The diagram compares planets of the inner solar system to Kepler-186,
a 5-planet system about 500 light-years from Earth in the constella-
tion Cygnus. The planets of Kepler-186 orbit a star classified as a M1
dwarf, about half the size and mass of our sun. The Kepler-186 system
is home to Kepler-186f, the first validated Earth-size planet orbiting
a distant star in the habitable zone - a range of distances from a star
where liquid water might pool on the surface of an orbiting planet.
The discovery of Kepler-186f confirms that Earth-size planets exist in
the habitable zone of other stars and signals a significant step closer
to finding a world similar to Earth. Kepler-186f orbits its star once
every 130-days and receives one-third the heat energy that Earth does
from the sun, placing it near the outer edge of the habitable zone.
The Kepler space telescope, which simultaneously and continuously
measured the brightness of more than 150,000 stars, is NASA¡¯s first
mission capable of detecting Earth-size planets around stars like our
sun. Credit: NASA Ames/SETI Institute/JPL-CalTech.
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Five small planets have been found orbiting this star,
four of which are in very short-period orbits and are
very hot. The planet designated Kepler-186f, however,
is earth-sized and orbits within the star¡¯s habitable
zone. The Kepler evidence for this planetary system
comes from the detection of planetary transits. These
transits can be thought of as tiny eclipses of the host
star by a planet (or planets) as seen from the Earth.
When such planets block part of the star¡¯s light, its
total brightness diminishes. Kepler detects that as a
variation in the star¡¯s total light output and evidence
for planets. So far more than 3,800 possible planets
have been detected by this technique with Kepler.
The Gemini data utilized the Differential Speckle Sur-
¡°It¡¯s simply remarkable that
we can look inside other
solar systems.¡± - Steve Howell,
Kepler¡¯s Project Scientist