Transcript Gemini South telescope makes the case for multiple Earth

National Science Foundation • Division of Astronomical Sciences
Gemini South telescope makes the case for multiple
Earth-sized planets
Prepared by the Association of Universities for Research in Astronomy
National Science Foundation • Division of Astronomical Sciences
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Nearby Exo-Earth Family Withstands Extreme Scrutiny
Astronomers combined the power of the 8-meter Gemini South telescope in Chile with the extremely high-resolution camera
called the Differential Speckle Survey Instrument (DSSI) to scrutinize the star TRAPPIST-1, confirming that the star is not a
binary and that the presence of several Earth-sized planets is consistent with earlier observations.
Previous observations of the star revealed dips in the star’s light, which would
be expected if several small planets orbited the star. However, the conclusion
that the star is host to these Earth-sized planets depends on the star’s being a
single object (i.e., not a binary, or twin, star). The Gemini data show no star
companions to the primary “host” star, to within a distance that is less than
that of Mercury from our Sun.
Faint “M-class” stars such as TRAPPIST-1 are of great interest to astronomers:
their diminutive size allows easier detection of small, terrestrial planets. In the
TRAPPIST-1 system, two of the planets appear to be very close to the host star,
with orbits of 1.5 and 2.4 days. Characteristics of the third planet are more
uncertain, but it is estimated to be within the habitable zone, where liquid
water could exist on the planet’s surface.
Gemini’s result came from the NSF-supported DSSI instrument, which provides
extreme-resolution imaging by taking multiple short (60 millisecond) exposures
to capture fine detail and “freeze” the turbulence caused by Earth’s
atmosphere. With this technique, the final images yield a resolution equal to
what the Gemini telescope would produce if it were in space. Thus, Gemini can
uniquely resolve such faint, distant objects.
Artist’s concept of the view from inside the TRAPPIST1 exoplanetary system showing three Earth-sized
planets in orbit around the low-mass star. This alien
planetary system is located only about 40 light years
away. The Gemini South telescope provided the
highest resolution images ever taken of the star, and
found no additional stellar-mass companions. This
provided strong evidence that three small, probably
rocky, planets orbit this star.
Prepared by the Association of Universities for Research in Astronomy