The commissioning of Zorro occurred May
20-23, 2019, when the team from NASA
Ames who designed and built the instru-
ment (Steve Howell, Nic Scott, Rachel Mat-
son, and Emmett Quigley) came to Gemini
South to assemble, install, and calibrate the
instrument. Despite some battles with the
weather, the first science run started imme-
diately after commissioning.
Science with Zorro
What kind of science can benefit from the
diffraction limited images delivered by Zor-
ro? The main science driver of the renais-
sance of speckle interferometry has been
the study of stars hosting exoplanets. The
study of exoplanets has been revolutionized
with dedicated space missions like NASA’s
Kepler (now retired), K2, and Transiting Exo-
planet Survey Satellite (TESS), which have
discovered thousands of new exoplanets via
the transit method — that is, the little dips in
the light curve of a star when a planet passes
in front of (transits) it. As impressive as these
missions are, they have one problem: be-
cause they observe large fields of view con-
taining hundreds of thousands of stars, their
pixel scales are necessarily coarse, several
arcseconds or more.
But what if the transited star is actually a
binary star? The properties of the planet de-
rived from the light curve can change radi-
cally whether the planet is transiting one
or the other star. This is where the power of
Zorro is manifest. Following up stars with
transits observed by Kepler/K2 and TESS and
looking for close stellar companions, it can
confirm and clarify the nature and proper-
ties of detected exoplanets.
One example is the newly discovered giant
planet KELT-25b with a 4.4 day orbit around
its parent star. This discovery was possible
with a combined analysis of the Kilodegree
Extremely Little Telescope (KELT) and TESS
January 2020 / 2019 Year in Review
data. Zorro observed this system during its
first science run and ruled out the presence
of any other unresolved stellar companion,
confirming the inferred size of the planet.
But the research done with Zorro does not
stop there. Its exquisite image quality can
also be used to study the whole zoology of
binary stars, multiple stellar systems, Solar
System objects, and maybe even to do some
extragalactic science.
Zorro is now commissioned and ready to do
science. What can you do with images hav-
ing a spatial resolution of ~15 miliarcsec-
onds? We wait for your observing proposals
by the end of September!
Figure 3.
The Zorro commissioning
team — from left to right:
Rachel Matson, Steve
Howell, and Nic Scott
(NASA Ames) — together
with Gemini South Sci-
ence Operation Specialist,
Joy Chavez, look happy
after achieving first light.
The selected target was
the star N Velorum.
Figure 4.
Kelt-25 as seen by Zorro.
The Zorro observations
show Kelt-25 has no stel-
lar companions, thereby
confirming the nature
of the newly discovered
transiting giant planet
KELT-25b.
Credit: Joey Rodriguez,
Sam Quinn, and Josh
Pepper (KELT-TESS); Steve
Howell, Nic Scott, and
Rachel Matson (NASA
Ames)
Ricardo Salinas is an Assistant Scientist at Gemini
South. He can be reached at:
[email protected]
Steve Howell is the Space Science & Astrobiology
Division Chief at NASA Ames. He can be reached
at: [email protected]
GeminiFocus
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