Our team aptly named the two
permanently mounted instru-
ments Zorro and ‘Alopeke (Figure
1), which come from the Span-
ish and Hawaiian (respectively)
words for Fox — because the in-
struments are both speedy and
sly like foxes. The instruments
were built to take advantage of
innovation and crafty approaches
to problems with only a fraction
of the resources necessary for
most 8-meter-class telescope in-
struments.
The power of these instruments
was demonstrated when Howell and his
team used ‘Alopeke to probe the Kepler-
13AB system. ‘Alopeke sharply resolved the
two stars (Kepler A and B), and captured a
clear drop in the light from Kepler A, proving
that the planet orbits the brighter of the two
stars. Moreover, as ‘Alopeke simultaneously
provides data at both red and blue wave-
lengths, the researchers could see that the
dip in the star’s blue light was about twice as
deep as the dip seen in red light.
As a very extended atmosphere would more
effectively block light at blue wavelengths,
the researchers characterize Kepler-13b as
a Jupiter-like gas-giant exoplanet with a
“puffed up” atmosphere due to exposure to
the tremendous radiation from its host star;
Thus, these multi-color speckle observations
give us a first tantalizing glimpse into the ap-
pearance of this distant world orbiting a star
in a binary system — something we know
very little about.
Our work with Kepler-13b stands as a model
for future research on exoplanets in multiple
star systems. The observations highlight the
ability of high-resolution imaging with large
telescopes like Gemini, not only to assess
which stars with planets are in binaries, but
also robustly determine which of the stars
the exoplanet orbits.
January 2020 / 2019 Year in Review
The Rise and Promise of Speckle
Imaging at Gemini
Speckle imaging at Gemini began in 2012
when the Differential Speckle Survey Instru-
ment (DSSI; designed by Elliott Horch) came
to the Observatory as a visiting instrument.
This precursor to ‘Alopeke and Zorro was
granted 10 hours on Gemini North to ob-
serve high-priority planet candidates from
NASA’s (now-retired) Kepler mission, whose
prime objective was to explore the structure
and diversity of exoplanetary systems, in-
cluding estimating how many planets there
are in multiple-star systems.
Figure 1.
The ‘Alopeke/Zorro
team at Gemini North
preparing ‘Alopeke for
installation.
Credit: Alison Peck
To search for planets around other stars, the
Kepler Space Telescope would stare at thou-
sands of stars and look for a slight decrease
in brightness, indicating that a planet had
transited (crossed in front of ) the star as
viewed from Earth. While the transit method
is very successful at finding planets, other
phenomena can mimic the signature of a
planet. Because of this, other methods must
be used to confirm whether a planet caused
the star’s dimming.
High-resolution speckle imaging enables as-
tronomers to not only resolve other objects
near the star hosting the planet candidate,
but detect or rule out other, non-planetary
GeminiFocus
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