Gemini South Observatory



The day that our team traveled to Gemini South was very exciting.  It would be our first contact with the  “big” telescopes.  We had departed from the seacoast town of La Serena, all of us traveling in a large van up into the Andes. Winding through the lower foothills of rural farmland we would occasionally get a quick glimpse of the white-domed observatory far ahead and high above. But the dry, dusty road could not even hint of our delight when we reached the top.


It seemed that, all of a sudden, we were in the high Andes and the view was spectacular.  For a few moments it wasn’t the view of the giant observatory dome that captivated us, but rather the snow-caped peaks. They were stunning! I’m sure, at least in a low voice, I must have said “Oh My God!” with my breath being taken away. Jumping out of the van, we planted our feet on the ground and breathed in the cold, dry air at 9000 feet elevation.  Exhilarating indeed!

And, of course, every one of us wanted to have our picture taken in this gorgeous setting!

The dome in the two pictures above is of the SOAR (Southern Astrophysical Research) Observatory.  It is smaller than Gemini South, shown in the picture below, but SOAR is a high quality observatory in its own right.  It is operated by the same group that operates Gemini.  As our first experience inside a major observatory we were able to go inside, see the telescope up close and talk to the technicians and engineers that run SOAR.

But moving along….even at 9000 feet many of us chose to walk (some ran) the several hundred feet up the road to Gemini South.  We were huffing and puffing a bit when we arrived, but I think our excitement at finally being there overcame any lack of oxygen to our brains. As you can see, it’s a very impressive structure.


Gemini South ( is an optical and near-infrared observatory.  It is managed by Associated Universities for Research in Astronomy (AURA) located in La Serena, Chile.  However, the important aspect to me is that it is funded by a partnership between the following countries: Argentina, Australia, Brazil, Canada, Chile, South Korea and the US. The US funding comes through our National Science Foundation (NSF). As we entered the lower level of the observatory the flags of the participating countries were quite evident.

We were all anxious to get upstairs to see the actual telescope, but we made a brief stop in the control room.  Control rooms for major telescopes these days are probably quite similar. They contain numbers of computer monitors as you can see in the photo.  Some are keeping track of the weather. Others monitor the status of the telescope and control its positioning.  Still others control the cameras and display the images as they are taken. And of course there are computers used by the astronomers during observing sessions to analyze the images they have requested.


Observatories are typically identified by the diameter of the mirror in the telescope.  In the case of Gemini South its mirror has a diameter of 8.1 meters, approximately 27 feet!  A mirror of that size is extremely heavy, and the associated structures, secondary mirrors and cameras can weigh hundreds of tons!  The machinery to move such a heavy weight in a smooth manner is a considerable engineering achievement.  When we arrived at the upper floor of the observatory we were greeted by this huge structure. I give credit to my colleague, Ed Ting, who took this photo with his fish-eye lens. 

And of course I had to have my own photo taken in front of this giant telescope!

We were all curious to see this giant in motion.  So the technical crew obliged. Click on the video below and have a look for yourself.  My voice and a few others are in the background.  We were all amazed at how smoothly the telescope moves. The fine-tuning and lubrication of the gears is incredible.

Gemini in motion

Gemini in motion

Play Video


Because our visit was during the day, the dome was closed and the telescope pointed straight up.  The giant mirror is held by the dark blue structure and cannot be seen in the photos above. Fortunately I was able to find on the Gemini South website a nearly identical photo that they had taken one night during a full moon.  In this photo the telescope is tilted toward you slightly. Look carefully to see the circular surface of the mirror at the bottom portion of the telescope.  Its diameter can give you an idea of the scale of the entire telescope.

The mirror is rarely uncovered during the day but, once again, the technicians treated us. We went up onto a platform that overlooks the mirror and they opened up a portion of it for us to see. The mirror surface is so finely machined and polished that I thought I was looking into a pool of water.  See for yourself!

At the risk of loading up this page with too many "pretty pictures", I've got to include this next one.  Stepping down from the platform to view the mirror, we all became mesmerized by this gorgeous view of the Andes through the side windows of the observatory. The location of this observatory, at least in winter, is stunning! I'm sure everyone took a photo of  this.  You see the SOAR observatory in the distance.


The Gemini South observatory is a state-of-the-art optical observatory.  It regularly upgrades its cameras and associated equipment so that it can capture the most precise images.  I'd like to focus on one piece of amazing technology called Adaptive Optics (AO in astronomers lingo).

When the light from a distant astronomical object comes through our atmosphere it is typically distorted by the water vapor and other gases.  Even in a nearly ideal setting like 9000 feet up in the Chilean Andes there can be some constant movement in the atmosphere that causes the images to be blurry. AO technology has the ability to counteract this movement so that the images are much sharper than without it. I am not qualified to explain in detail how Adaptive Optics works, but I'll share with you my current understanding below:

There are many components to this complex system. First of all an artificial star pattern is created in the sky by a set of 5 lasers. If you look at the photo to the right  (from the Gemini South website) you will see a beam of yellow light shooting up out of the observatory and into the night sky. It looks like a single beam, but take a close look at the magnified image to the upper right. You'll see a pattern of 5 dots, kind of like a mini constellation of stars.

Next in the sequence is that the camera on the telescope takes an image of these stars. Because of the distortion by the atmosphere that image will be correspondingly distorted/blurred.  But....the "system knows" what the image is supposed to look like so it can feed back into the data a correction to make the image much clearer.  This process is happening constantly and, nearly, instantaneously.  So the image that appears on the astronomer's computer screen is already corrected.

I readily admit that the paragraph above contains a whole lot of missing information about technology that's highly sophisticated.  I'm simply awed by what it can do! And what it does do is to take images that are very good but lack clarity and some detail, and turn them into high quality, detailed images.

In the poster to the left (photographed in the hallway of Gemini South) is a detailed explanation of how AO works.  I draw your attention, solely, to the two images of a star field on the left side of the poster. The one in the upper left is without AO.  The one at the bottom is with AO.  I hope you can see the difference in the clarity of the stars.


So, finally, that brings me to share with you a few images, taken at Gemini South, that represent some of the capability of this amazing observatory. They also represent the major areas of research that is being done by the international group of astronomers and astrophysicists. I downloaded them from the website gallery. They are ordered from left to right in terms of their distance from the earth.


Saturn, of course, is in our solar system, relatively nearby.  The Brown Dwarf is a star outside our solar system "only" hundreds of light years away.  Reflection Nebula GGC27 is about 5500 light years away but within our Milky Way galaxy.  Starburst Galaxy NGC 1313 is well outside the Milky Way at 15 million light years.  The Polar Ring Galaxy 40 million light years away.  Abell 3827 shows galaxies 1-2 billion light years away.  Yes, Billion!

Saturn with Titan, its largest moon.

Brown Dwarf, Wise 855bd (artist's conception)

Reflection Nebula GGC27 (a stellar nursery birthing stars)

Starburst Galaxy NGC1313 (unusually high rate of star formation

"Smashing" Polar-Ring Galaxy (collision of 2 galaxies)

Abell 3827 (deep field view of thousands of galaxies)


Gemini South is one of the major observatories in the world, located in near-ideal conditions in the high Chilean Andes. It has an identical twin, Gemini North, located on the Big Island of Hawaii. Together their Mission Statement is as follows:

"To advance our knowledge of the Universe by providing the international Gemini Community with forefront access to the entire sky."

In my limited but very personal experience at Gemini it seems to me that this "Community" is very fortunate to have such a facility.  To add to the state-of-the-art technology and the excellent sky and weather conditions is the beauty of the setting.  Were I a research astronomer I would be inspired by that earthly beauty to seek the wonder and magnificence that is out there in the near and distant Universe!

If you want to continue on to the next observatory just click Cerro Tololo.