The astronomical observatories in Chile

High in the Chilean Andes, beneath some of the darkest skies on Earth, world-leading observatories are reshaping our understanding of the universe - each in their own unique way. I had the amazing opportunity travel to Chile as an ACEAP Ambassador.

The Astronomical Observatories in Chile (above)

The Astronomy in Chile Educator Ambassador Program (ACEAP) is a collaboration between Associated Universities Inc (AUI) and the Association of Universities for Research in Astronomy (AURA) and the observatories they manage in Chile, including Vera Rubin, Gemini South, CTIO, ALMA, Kitt Peak and others. The program brings amateur astronomers, STEM educators, planetarium and observatory personnel together for an intensive immersion at many of the top astronomy facilities in Chile.  When they return home, Ambassadors share their experiences and explain the value of the research and science being performed there. To learn more about ACEAP visit www.astroambassadors.com

By 2040, 80% of the world’s top observatories are expected to be located in Chile. This is my experience, when visting the Observatories in Chile

Why? Chile checks all the boxes:

• 330 clear nights/year
• Exceptional steady atmosphere
• Low humidity
• Low labor and materials costs for construction
• Site availability
• Excellent power/internet/roads infrastructure
• Stable government (important for $1B investments!)

Alfa Aldea Observatory

Our first stop was the Alfa Aldea Observatory. This is a business that supports astronomy tourism and is open to anyone. We had a nice 3D presentation, then did astrophotography under very dark skies.  The observatory had a 16” Dobsonian telescope and we looked at many of the southern hemisphere’s favorite targets: Omega Centauri, Centaurus A, the Jewel Box star cluster, Eta Carina, and the Magellanic clouds. For some in the group it was their first experience under dark southern hemisphere skies and they were amazed.

Gemini south observatory (above)

Cerro Pacho

The next day we drove to Cerro Pachon, which is the mountain that hosts the Vera Rubin, Gemini South, and SOAR observatories.

The Gemini South Observatory is one of two telescopes that make up the international Gemini Observatory.  Gemini North is located on Mauna Kea in Hawaii, enabling 100% sky coverage.

Gemini South features an 8.1-meter mirror and utilizes adaptive optics to correct for atmospheric distortion, providing near space-quality images.The observatory plays a crucial role in research on exoplanets, supernovae, black holes, galaxy formation, and more.

Imagine looking at a pebble at the bottom of a pool. If there are ripples on the surface, the pebble will appear distorted. The same thing happens when a telescope has to look through our atmosphere – it’s why stars appear to twinkle. One mitigation is to place the telescope as high as possible in a dry climate to get above the heavier, more distorting air.

But you can also use adaptive optics. In adaptive optics, a laser creates an artificial star.  The light from that star is measured and the amount and type of wobble is detected.  The computer then instantaneously computes what deformation of the mirror is needed to cancel the wobble, and tiny actuators on the mirror minutely deform it in real time.

With adaptive optics, telescope delivers an incredible resolution of 0.06” in visible light.  In the near infrared, Gemini can approach 0.04”.

The field of the view of the telescope is 5 arcminutes, which is about 1/6 of a moon diameter. It has a focal ratio of F16.

All new large observatories now use Alt Az mounts because compared to equatorial mounts they are stronger, lighter, simpler, cheaper, and equally precise.  Field rotation issues are handled by de-rotators on the camera or spectroscope.

The technology behind Gemini drives innovation in optics, imaging, and data analysis, with applications in fields like medical imaging and telecommunications.

For more information on the Gemini observatory, visit https://www.gemini.edu/

Vera Rubin observatory (above)

SOAR

We then walked 200m down the road to the SOAR telescope.
This is the Southern astrophysical research telescope

SOAR has a 4.2m mirror with adaptive optics, and a 1/2 degree field of view, about the size of the full moon.

SOAR is optimized for seeing into the UV spectrum, thus it’s mirror is coated with Aluminium, which reflects UV light better than silver.

It has a 0.3” resolution when looking at a wide field. In high resolution, narrower field of view mode, it can approach 0.030” with adaptive optics under good conditions.

Vera Rubin

We were the first group to see the Vera Rubin observatory since its initial photos were published, and were allowed unprecented access to the telescope, control room, engineers and scientists. Some fast facts about the observatory:
Located on Cerro Pachon mountain at an elevation of 2682m
Unique-shaped building designed to optimize laminar airflow on the mountain to maximize seeing conditions at the telescope

• 8.4m mirror
• Extremely fast focal ratio of 1.2
• Alt azimuth mount
• 3.2 gigapixel cryogenically cooled camera - the largest digital camera in the world field of view equal to 40 full moons – largest of any major observatory
• Captures 20 terabytes of data per night
• Plan is to image the entire southern sky 825 times over 10 years

In its first image, it captured 10 million galaxies.  It’s optimized to find transient phenomenon like asteroids, comets, near Earth objects, supernovae etc. 
Interesting side note -  size of the mirror was limited by the diameter of a tunnel the mirror had to pass through on the way from the coast to the observatory in the Andes. When it passed through the tunnel there was 10cm clearance on each side.

The Telescope has Active optics not adaptive optics

Adaptive optics systems work by correcting for rapid atmospheric turbulence over a relatively small patch of sky. But turbulence varies across different lines of sight, and Rubin sees enormous swathes of sky at once, so correcting across such a wide field at once is practically impossible.

With Active optics, the telescope corrects slow, low-frequency distortions in the the mirrors due to gravity, temperature, and mechanical stress. The idea is to maintain the ideal mirror shape over long periods of time.  This technique is used because the field of view is so huge. Remember, Rubin’s goal is rapid, wide field images of large parts of the sky. Active optics achieves this.

So in summary, Adaptive optics are suited to narrower fields of view. Note that the field of view of the Gemini south telescope is 1200x smaller than Vera Rubin.

Another interesting note is that it is not the “Vera Rubin telescope”.  It is the Simonyi Survey Telescope. Charles Simonyi made the initial large donation to fund the casting of the primary mirror for the telescope.

Rubin will scan the sky in unprecedented detail, capturing billions of galaxies and countless transient events like supernovae, flaring black holes, asteroids and comets, enabling rapid follow-up observations by other telescopes, including Gemini.

CTIO

CTIO stands for the Cerro Tololo InterAmerican Observatory, and includes dozens of telescopes and an automated solar observatory.

Cerro Tololo is a nearby mountain to Cerro Pachon. You can easily see observatories on one mountain from the other.

The first night we arrived we toured the Victor Blanco telescope, which is a near twin to the 4m Mayall telescope on Kitt Peak.

Despite being 50 years old, it still operates at peak efficiency and generates over 300 research papers per year. This pace of discovery will quickly be surpassed by the Vera Rubin, but for the last 7 years it has been the most productive telescope in the world in terms of scientific papers generated.

It has 4m, aluminum coated mirror and a special dark energy 570 megapixel camera. This gives it a 3sq degree field, generating 1TB of data per night. It’s designed for wide field surveys in the Infrared.

The largest comet ever discovered found with this scope, along with much of the original data that proved the acceleration of the universe.

The next day we visited what they call the Mushroom farm – a large number of smaller domes with national or university-owned telescopes which range from 25” to 80” mirrors.

ALMA

Next we traveled to San Pedro de Atacama, and then to ALMA. 
ALMA is the Atacama Large Millimeter sub millimeter Array. The Operations support facility is located at 2900m/9500ft elevation, while the radio telescopes are located up at 5050m/16,400 ft.

There are 66 radio telescopes which can located in any of 197 sites. The telescopes are moved with gigantic machines. They were custom made in Germany and can lift and move any radio telescope and place it on a new pad in the array.

There are 54 12 meter dishes and 12 7 meter dishes. ALMA is capable of 0.005” resolution which was used to directly image the first protoplanetary disk system.

Water vapor absorbs millimeter and sub millimeter radiation so this site, perched so high and in such a dry location, is ideal for this type of radio astronomy.

Alma AOS

One of the challenges is correlating the signals from multiple antennas located at different and changing distances from the facility. To do that they have a
Rubidium clock accurate to 1 second every 2 million years, and several supercomputers.

Due its extreme altitude, ALMA is considered the second toughest operating environment of any observatory. Can you guess #1?  South Pole Telescope. Fun Trivia –  The SPT has an annual ‘round the planet 5km run’ and you get a diploma for running around the world!

Radio telescopes can be moved which affects field of view and resolution. 16km baseline maximum gives highest resolution, and the smallest FoV. Putting them closer together gives a wider field of view at lower resolution.

ALMA is a great complement to the Very Large Array in New Mexico. As you can see from the diagram they cover adjacent parts of the radio spectrum.

Benefits of astronomy research

• Remember exploratory surgery? It is now almost a thing of the past now that we have advanced diagnostic imaging like CAT scans and MRI. These capabilities were derived from aperture synthesis technology used by radio astronomers. The resulting savings in lost productivity and healthcare is in the trillions of dollars
   
• Imagine a satellite in space taking pictures of the Earth and having to eject a film canister so the pictures could be developed. That’s how it used to work. Space exploration and imaging led to the development of digital cameras. The photos you take with your smart phone have roots in astronomy research.
   
• GPS would not be possible without an atomic accuracy clock which in turn requires knowledge of pulsar timing. And GPS also needs quasars to calibrate precise knowledge of earth rotation.
   
• Do you have home insurance for a fire or other catastrophic event? Vera Rubin is going to catalog millions of asteroids and near earth objects, allowing us to identify any that might pose a risk and have time to deflect them away. Solar observatories help us understand space weather and mitigate the risks of inevitable solar flares and coronal mass ejections pointed at Earth.
   
• Satellites and space observatories require lightweight, durable alloys and composite materials – these materials science advances have been adopted in aviation and automotive applications.
   
• Handing massive amounts of data from telescopes like ALMA, Gemini and Vera Rubin have led to advancements in data processing and machine learning with applications in finance, healthcare and cybersecurity.
   
• Techniques for studying cosmic rays have led to advancements in precise targeting of tumors in cancer treatments.
   
• Astrophysics research into stellar fusion is likely to one day lead to clean, plentiful, ultra low cost energy for all.
   
• Satellite technology improves communications and entertainment, supports national defense, and enables climate science.
   
• Astronomy and space exploration inspires students to choose STEM fields of study, increasing science literacy and workforce skills.
   
• Understanding fundamental forces of nature like black holes, dark energy, and dark matter may seem abstract today but often leads to breakthroughs that can positively impact daily lives. For example Einstein’s relativity was initially dismissed as a fanciful thought experiment, yet now underpins GPS and nuclear energy. And while quantum mechanics may seem completely abstract it helps explain fusion and many astronomical principles, and it led directly to the transistor, integrated circuits and computers.

CTIO observatory (above)

My time in Chile increased my appreciation for value of the work they are doing there.  The US spent just 0.09% of the 2024 budget on astronomy-related research. We get an incredibly good return on our investment in astronomy research!