Astronomy

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World-class observatories
We spent two nights at CTIO, touring
the observatory by day and forgoing sleep
to stargaze at night. ACEAP encourages
ambassadors to document their trip every
step of the way; we filled much of our sched-
uled “downtime” with image processing,
blogging, or posting on social media. Some
spoke with students back home via webcam.
The experienced astroimagers generously
shared tips — and even equipment — with
those of us new to night-sky photography.
We toured the 4m Víctor M. Blanco
Telescope and the Yale 1m telescope, part
of the multinational Small and Moderate
Aperture Research Telescope System.
Our visit also took us to nearby
Cerro Pachón, where the 4.1m Southern
Astrophysical Research Telescope and the
8.1m Gemini South Telescope reside along
with the construction site for the Large
Synoptic Survey Telescope. We climbed
the steps alongside the towering Gemini
Telescope to see its silvered primary mirror
up close, and craned our heads back as tele-
scope operators opened the dome and

PHOTOS FROM CHILE

moved the telescope, the entire dizzying

process smooth and nearly silent.

In the Atacama Desert, we visited local

schools in San Pedro and Toconao with

two 2016 ambassadors who’d returned to

Chile for outreach. We observed science

classes and gave live demonstrations on

topics such as infrared light and safe solar

viewing. (Chile lies in the path of totality

for the July 2, 2019, solar eclipse.) We

handed out eclipse glasses, maps of the

Moon, and photosensitive beads to pri-

mary and high school students.

Our visit to ALMA began at the

Operations Support Facility (OSF) at

9,500 feet (2,900 m) in elevation. It con-

tains staff offices, labs, and the telescope

control room where astronomers observe.

In one lab, we saw several of ALMA’s

front-end receivers, which digitize and

amplify signals received by the dishes.

The general public can visit the OSF,

but few people — astronomers included

— visit ALMA’s Array Operations Site

(AOS) 17 miles (28 kilometers) away, where

the antennas sit on the Chajnantor Plateau

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16,500 feet (5,000 m) above sea level. We

were invited to visit the AOS, provided we

passed a mandatory physical and observed

a two-hour time limit. Traveling to high

altitude raises both heart rate and blood

pressure, so our vitals were checked that

morning. We were all cleared for the trip.

The day was clear and crisp with a deep

blue sky, and the often-windy plateau was

relatively calm with scattered piles of crys-

talline snow and spiky fields of ice. Each of

us carried an oxygen tank; at that altitude,

the atmosphere contains only about 55 per-

cent of the oxygen it does at sea level. First,

we toured the AOS Technical Building, the

world’s second-highest building, which

houses the correlator supercomputer.

Capable of performing 17 trillion calcula-

tions per second, it combines signals from

the observatory’s 66 radio dishes, allowing

them to work as a single telescope.

Next, we drove out to walk among the

100-ton antennas, some rotating — swiftly

and silently like their optical counterparts

— in testing mode. We marveled at the

engineering, ingenuity, and perseverance

1. ALMA’s 100-ton antennas stand scattered
   against the deep blue sky. This backdrop is
   only visible at the extreme altitude necessary
   to ensure perfect observing conditions at
   millimeter and submillimeter wavelengths.
   M. DIETERICH (@MATTDIETERICHPHOTOGRAPHY) (ACEAP/NSF)


2. ACEAP ambassadors Alice Few (left) and
   Amy Jackson consult a planisphere as they get
   ready to view the southern sky for the first time
   from the Observatorio Astronómico Andino near
   Santiago. A. OSTERMAN MEYER (ACEAP/NSF)


3. While taking a self-portrait with the Milky Way
   and Magellanic Clouds, I serendipitously caught
   a shooting star. ALISON KLESMAN (ACEAP/NSF)


4. At the Toconao school near ALMA,
   the ambassadors engaged in a morning
   of exploration with young students eager
   to learn more about astronomy, physics,
   and biology. ALISON KLESMAN (ACEAP/NSF)


5. This colorful panoramic view captures several
   of the telescopes and other buildings atop
   Cerro Tololo at the Cerro Tololo Inter-American
   Observatory. D. DEMETER (ACEAP/NSF)


6. The design of the Gemini South Telescope
   dome includes 33-foot-wide (10 m) vents to allow
   airflow and regulate the temperature inside
   the dome for better image quality. These vents
   also provide a stunning view of the surrounding
   mountains during the day. ALISON KLESMAN (ACEAP/NSF)


7. On the drive to ALMA’s Array Operations Site
   at nearly 16,500 feet (5,000 m), we spotted
   several vicuñas. These relatives of the llama
   don’t mind the high altitude. ALISON KLESMAN (ACEAP/NSF)