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Crossing Borders and the Equator: An Astronomy Ambassador in Chile. Part 1 - Optical Observatories - Cerro Pachon

By Derek Wallentinsen posted 03-05-2023 18:06

  

Chile has a unique geography. Stringbeaning over 4000 kilometers north to south and only 400 kilometers wide is only part of it. It also contains some of the highest and driest mountains in the world. The Andes Cordillera rises up to almost 7000 meters and thanks to the Humboldt Current carrying cold Antarctic waters almost to the equator, precipitation is very low. The combination of aridity and few clouds means the country and the range are the best places in the world for astronomy. Because of the convergence of favorable conditions for astronomy, by 2030, Chile will host nearly 70% of the world's astronomical infrastructure, virtually all of it in the northern third of the country.


Northern Chile - Astronomy Capitol of the World

As an American astronomer, I'd long dreamed of looking up at Chilean skies. In December 2022, my dream came true as I had the good fortune to be part of a group visiting several major observatories in Chile. The Astronomy in Chile Educator Ambassadors Program (ACEAP) is a collaboration between Associated Universities Inc. (AUI) and Association of Universities for Research in Astronomy (AURA), and the observatories they manage in Chile. ACEAP's goals are for ambassadors to learn firsthand about Chilean astronomy and then to share that experience with others. Institutions involved in one way or the other in locations we visited include the National Science Foundation's NOIRLab (National Optical-Infrared Astronomy Research Laboratory) and the National Radio Astronomy Observatory. Many ambassadors are amateurs active in outreach or formal and informal astronomy educators at planetaria and schools.

 

Astronomy in Chile Educator Ambassadors Program emblem

We were able to see and learn about the Cerro Tololo InterAmerican Observatory (CTIO), Gemini South, Vera Rubin Observatory and ALMA (Atacama Large Millimeter/submillimeter Array).

The trip from Albuquerque through Dallas to Santiago took most of a day. The nine-hour flight from the US to Chile was at night. I spent much of my waking time looking at clusters of lights in remote places like the Yucatan and spotting Canopus and Archenar. Dawn came while airborne and dramatically revealed the mountains to the east. The Andes - numero uno in astronomy!

The Andes - Numero Uno in astronomy!

After enjoying a bit of Santiago in the Vitacura district, then a day of orientation at AUI's Chilean headquarters, the ambassadors flew to the coastal city of La Serena. Here CTIO has offices and many who work at the observatories located 100 km away to the east live here. I couldn't resist exploring the Pacific Ocean, only 100 yards from our hotel.

Sky Costanera - Tallest Building in South America - Santiago
AUI Headquarters
La Serena and Coquimbo
Océano Pacífico

Because of its atmospheric superiority, the country has a burgeoning astrotourism segment. Centro Astronomico Alfa Aldea is located in Vicuna in the Valle de Elqui east of La Serena. It's one of several "touristic" observatories in the town. After hearing several enthusiastic talks from both the proprietors and CTIO people, then enjoying wine and tapas, we got great views of objects like the Tarantula Nebula and 47 Tucanae through their CPC 800. Despite some bright lights a mile or so away in the town, my Sky Quality Meter read 20.6, much darker than most parts of the continental US.

Centro Astronomico Alfa Aldea

Next morning, we departed for CTIO up Chilean Highway 41, Ruta de la Estrellas (Route of the Stars). Soon the domes loomed on the ridges ahead of us. We passed by Cerro Tololo (from the Quechua language: The Hill at the Edge of the Abyss) and stopped first at the imposing dome of the Gemini South Telescope. Inside, dwarfed by the 8-meter-aperture of the Gemini South Telescope atop Cerro Pachon, the ACEAP 2020 cohort learned about the inner workings of this great telescope.

Cerro Tololo
Cerro Pachon
Gemini South 8-Meter Telescope

Located at 2700 meters or about 9000 feet, this telescope uses adaptive, distortable optics with five lasers creating artificial stars high in the atmosphere to greatly reduce the effects of looking through turbulence (seeing). The GEMS (Gemini Multi-Conjugate Adaptive Optics System) was mounted to the scope upon our visit. That's in addition to the active optics underlying the primary mirror to maintain its figure. The mirrors have special hybrid coatings in layers that include silver to reflect almost all visible and infrared light.

Gemini South's massive dome
Gemini Multi-Conjugate Adaptive Optics System

 

Although Gemini South (and its Hawaiian twin Gemini North) observe just about everything from the solar system to distant quasars, perhaps its most famous instrument is the Gemini Planet Imager (gee-pie), delivering direct images of planets around nearby stars. One example is 51 Eridani b, a Jupiter-mass exoplanet in a Saturn-sized orbit around a naked-eye star.
Picture of the 51 Eri system.


 GEMS in action at Gemini South
51 Eridani exoplanet (Credit Gemini South/AURA)

Our ACE Ambassadors then moved down the ridge to the 4-meter-mirror (Southern Astrophysical Research) telescope. SOAR observes from 30 degrees south of the equator, looking at the sky in optical and infrared wavelengths. An important project at SOAR is follow-up for TESS, NASA's Transiting Exoplanet Survey Satellite, to confirm the detection of worlds around other stars. It also studies the Magellanic Clouds and even imaged the aftermath of the asteroid-bashing DART mission in October 2022.

SOAR atop Cerro Pachon
SOAR is equipped with both active and adaptive optics
VISCACHA Survey of LMC and SMC. Credit SOAR, NOIRLab
Dimorphos 2 days after DART impact October 2022. Credit SOAR, NOIRLab.

 

Still abuilding, this uniquely-shaped structure is the Vera Rubin Observatory (VRO). Home to a 8-meter telescope, it will carry out the Legacy Survey of Space and Time. 

Vera Rubin Observatory

VRO's dramatic site atop Cerro Pachon


Named after the famous astronomer who found the first evidence of dark matter, it will continue that quest on top of many others. Taking images every 15 seconds through a series of filters, three lenses – including the largest lens ever made – and three mirror surfaces, the sweep will cover the entire sky visible from 30 degrees south every three nights.

Optical diagram of the Simonyi Telescope and camera at VRO. Credit Mason Pro. LSST


It will do this for 10 years, creating a huge astronomical database in both time and space domains. These snapshots will spawn 10 million alerts every night, terabytes covering everything from Solar System objects to redshifted supernova explosions at the edge of the observable universe. The data flow alone is as spectacular as the coffee-table-sized chip array that actually captures the images, the largest digital camera ever made. Unfortunately, due to technical construction safety reasons, our group of Astronomy in Chile Educator Ambassadors was only allowed into the control room of the observatory. Nonetheless, an awesome astronomical experience!

Next up: Crossing Borders and the Equator: An Astronomy Ambassador in Chile. Part 2 - Optical Observatories – Cerro Tololo.

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