Trip to Chile illustrates astronomical discovery

August 9, 2018 GMT

As promised, I’ll use a portion of this column this month to continue the highlights of my recent Astronomy in Chile Educator Ambassadors Program trip to Chile to learn about the astronomy being conducted in U.S.-funded observatories.

I often emphasize to my students the point that my role as a professor is to do more than just give them information about objects in space. If it’s only information they’re after, they can find that in books, videos or the internet. Rather, I also want them to understand how science is done. That is, when they hear about an exciting new discovery, I want them to know how we gain this knowledge because that’s the truly human part of the endeavor.

This past month saw an excellent example of this. Astronomers announced they had discovered 12 new moons orbiting the planet Jupiter. Since Galileo discovered the four largest moons of Jupiter when he first turned a telescope on the planet in 1610, Jupiter has proven to have a host of them. The latest count before this new discovery was 67. (These new moons make the total 79.)


It’s not a surprise Jupiter would have a large number of orbiting objects, as it is the largest body in the solar system besides the sun. Positioned near the main asteroid belt, it occasionally captures asteroids as moons. But the how of this discovery intersects the story of astronomy, as well as my recent trip to South America.

One of the first major American research observatories founded in Chile is on the peak of Cerro Pachon, 8,000 feet up the Elqui Valley, not far from the coastal city of La Serena.

The observatory there is known as CTIO, the Cerro Tololo Inter-American observatory, and it is home to almost 20 different telescopes, from the giant 4-meter Blanco telescope to several smaller instruments operated by universities and various remote observers. The observatory domes are so prevalent, the workers there refer to it as “the mushroom farm.”

The Blanco telescope was built in 1974 and for a time, was the largest telescope in the Southern Hemisphere. In 2012, it was equipped with the Dark Energy Camera, a project that involved physicists from Fermi Lab here in Illinois.

The DECam was fairly unique among astronomical research instruments because of its very wide field of view.

Whereas most telescopes have views of very small regions of the sky, the DECam was made to survey the entire sky, probing the distribution of galaxy clusters to map dark matter.

Cerro Tololo was our first major observatory stop on the ACEAP tour. We flew from Santiago to La Serena, where the organization that manages CTIO, as well as other nearby observatories ,is located.


June is winter in the Southern Hemisphere and there recently had been snow, but once the roads were cleared, we drove up the mountain to Cerro Tololo. The site was chosen because, similar to so many in Chile, the skies around it still are very dark, and the weather is clear and very dry. Indeed, before that year, the region had gone as long as five years with no measurable precipitation.

CTIO is fairly unique in that it has a lodge for visiting astronomers and workers, so we were able to spend the night on the mountain and see the Blanco telescope in action, as we will see the glorious southern skies for ourselves.

The night we were there, we watched the immense dome open and the huge telescope get ready for work. In the control room, we met an astronomer from Brown University who was doing research that evening, using the DECam to image galaxy clusters. The gravity of intervening objects can distort distant clusters by a phenomenon called gravitational lensing. This means that measuring the shape of clusters can give insight into unseen matter in the universe — what scientists know as dark matter. The DECam, with its wide field of view, especially is suited for this type of work.

But occasionally much closer objects make it into the DECam’s field of view. This was the case with the unexpected moons of Jupiter.

The moons were first detected when Jupiter was imaged by the DECam while conducting a different type of wide-angle survey, hoping to find objects at the very edge of the solar system in the Kuiper belt.

When astronomers noticed that Jupiter would be in their field of view, they decided to look for dim objects around it as well. After more than a year of work, the team confirmed the new moons.

Things such as dark matter and new moons discovered from the peak of a mountain in the Chilean Andes might seem pretty esoteric stuff, but what struck me is how places such as CTIO make it possible for us to continue to refine our perceptions of the universe.

Dark matter and dark energy shape the large-scale structure of the entire universe, and understanding the orbits of the clustered moons around Jupiter provides insights into how our solar system has changed throughout time. And the process of gaining these insights — building the instruments, maintaining and operating the telescopes — is a very human endeavor.


I’ll be speaking about the ACEAP program and more about astronomy in Chile on Saturday at FEED Arts Center in downtown Kankakee. My talk is titled (with apologies to the hit Netflix show) “SOUTHERN THINGS: Astronomy in the Upside Down,” as I’ll be reflecting on how the familiar sights of the northern sky are inverted when one travels to the Southern Hemisphere.

After the talk, weather permitting, there will be sidewalk observing to view Jupiter, Saturn and Mars through telescopes.

The talk and observing is free and open to the public.

Perseid meteors

Also this week, be sure to try to catch the Perseid meteor shower, which peaks Sunday evening and early hours of Monday.

The Perseid shower already is underway with increasing activity until this weekend.

It’s best viewed after midnight when the constellation Perseus has risen in the north, though meteors are visible throughout the entire sky.

On any clear night this week, take the excuse of a possibility of catching views of shooting stars to lay outdoors looking upward.

A meteor shower is a slow event; you need to watch for a long time, though each individual shooting star is quick. This year, the Perseids at their peak are projected to reach rates of perhaps 50 shooting stars per hour.

Sands stargazing

Friends of the Sands will host a star-gazing and Perseid Meteor Shower viewing for all ages beginning at 7 p.m. Saturday at the Kankakee Sands Seed Barn, off U.S. Route 41 between Lake Village and Morocco, Ind.

Bring lawn chairs or blankets to sit on and bring a favorite nighttime snack to share.

For more information and to RSVP for the event, contact Tom or Susan at