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Cerro Tololo Inter-American Observatory


We arrived at Cerro Tololo just after dark on a cold winter evening. CTIO is on a hill not too far from Gemini South, but at a slightly lower elevation.  We had seen the white domes of this large complex from Gemini, but it wasn't until morning, after being greeted by a beautiful sunrise, that we got the full view.  Click on the video below to get a larger, 360 degree view of this observatory.

Cerro Tololo 360

Cerro Tololo 360

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As you can see, Cerro Tololo is much more than a single observatory.  There are more than 15 different observatories on the site.  The largest and principal observatory is the Joseph M. Blanco Observatory which is the large, tall one on the left containing a 4 meter mirror.

But lower down on the hill are many, smaller observatories in the one-half to one meter range.  Some of these are owned and operated by private organizations, some to universities, and I saw one belonging to Thailand.  Several are available online to teachers and students which enables them to take and download their own, high quality images. We got a chance to go inside a few of these as we were walking up the hill to the Blanco Observatory. 


When astronomers refer to Cerro Tololo they're typically talking about the 4 meter Blanco observatory. It is an older observatory, commissioned in 1974.  But it is still making major contributions to current astronomical research.  I'll get to that in a minute.


But I'd like to take a brief side trip in history. As I've said in other parts of my website, I was in the Peace Corps in Valparaiso, Chile, during the years 1965-67. Unbeknownst to me, during 1967 then US President Lyndon Johnson and then President of Chile, Eduardo Frei, inked an agreement for the construction of "Blanco".  It was considered to be the first observatory carefully located in the southern hemisphere for superior atmospheric conditions. Because of that coincidence I feel somewhat personally connected to this observatory.

So let's head up to the Blanco! There's another piece of history I want to tell you about. It's a very impressive structure as you can see. Thanks to Angela Meyer, one of my colleagues on the trip, for taking that photo.  Coincidentally, Angela has a very personal connection to the Blanco since she actually did some research here several years ago.


Immediately inside the door of the observatory we came into a room just outside the control room for the telescope.  There on the wall was the poster you see below. The poster commemorates the 2011 Nobel Prize for Physics. It was awarded to two teams of scientists who discovered the accelerating expansion of  the Universe.  It has been known for nearly a century that the Universe is expanding, but that it is accelerating in its expansion was unexpected.

And why would this poster be here you ask? And why does it interest me so much? Well, it turns out that one of the two teams of scientists got much of their Nobel Prize data here at the Blanco. That team was the Supernova Cosmology Project located at Lawrence Berkeley National Laboratory. The team was headed by Dr. Saul Perlmutter. One of the members of his team is a personal friend of mine, Dr. Carl Pennypacker. Dr. Pennypacker was the founder of Hands-On Universe (HOU), the organization that I've had the privilege of working with for over 25 years. At one point we (HOU) provided Blanco supernova data to high-school students for use in our program.


Now to the telescope and its camera.  You see the Blanco telescope in the photo below. As I said earlier, the mirror on this telescope measures 4 meters in diameter.  In the photo you can see the mirror toward the lower right, just to the left of the dark blue structure. It has a white cover over it so you're not seeing the shiny surface that you would expect.  Toward the upper left is the camera (the long black structure). I'll say more about this special camera below, but you may be asking yourself, "Wait a minute! How does this whole thing work? The camera is out here in front of the mirror?" A brief explanation: When the dome is open the camera end of the telescope will be pointing up into the sky. Light rays come in, around the black camera and through the whitish ring structure.  They hit the mirror at the back end.  The parabolic mirror reflects and focuses the light and sends it back into the camera as an image.

Here's a good shot of most of our ambassador team in front of the telescope.  There are 3 of us missing (all men), including yours truly, but I took the picture.


The camera that you see in the photo above is called the DECam, the Dark Energy Camera. The details of this camera are described below, but let me explain the name first.  Again this is a bit of history.  When the discovery of the accelerating expansion of the Universe was first made it perplexed a lot of folks.  "Wait a minute....from our current understanding of the way things work, gravity should be slowing things down, not speeding them up! Hmmm...there must be something that is working against gravity, and we don't know what it is.  Well....let's call it Dark Energy!"  And the name was born. It is still perplexing and its source is still unknown.

There is currently a five-year study called the "Dark Energy Survey".  It's an international effort in its final year. Over 400 scientists from the following countries are involved: Australia; Brazil; Chile; Germany; Spain; Switzerland; United Kingdom; United States. The DECam was designed and installed on the Blanco to carry out this survey.  It's aim is to study 300 million galaxies from nearby to very far away (or back in time).  Since Dark Energy seems to work at the galaxy level, the idea is to see if there is some kind of pattern in how galaxies have changed during the last 7 billion years.  Finding a pattern will give some clues as to what Dark Energy is.


The DECam has to be one of the largest digital cameras in the world.  It contains 570 Megapixels. You might want to compare that to your cellphone camera of, perhaps, a measly 10 Megapixels. In the photo below left you see 2 technicians working on the camera.  The light-sensitive portion is contained within that circular ring. The photo to the right shows a simulation of a huge field of galaxies spread over the entire massive chip. Every white spot you see is a galaxy! To give you some idea of the capability of this camera, here is one amazing statistic (according to the CTIO website): Every image taken contains approximately 200,000 galaxies! (Photos taken from the CTIO website.)

The Dark Energy Survey recently reported the following:


*Data on ~310 million galaxies and ~80 million stars.

*Objects in the range of about 8 billion light years from Earth. 


*Mapped changes in these galaxies over a 7 billion year period. 


Where that will lead in terms of understanding Dark Energy remains to be revealed.


I'm sure you're interested in seeing some of the images that this camera has taken. Here is a sampling, once again taken from the CTIO website. Keep in mind that the aim of the DECam is to capture large fields of very distant (deep-field) galaxies.  However, there are sometimes beautiful structures, such as the ones you see, in the middle of the frame. These are "nearby objects". The globular star cluster on the left is actually in our Milky Way galaxy. The rest of the images contain spiral galaxies that are "only" tens of millions of light years away.  All the colored spots in the backgrounds of the images are the galaxies of interest, billions of light years away.


I want to end this page with one more experience.  During one of the nights at Cerro Tololo we were able to be in the control room of the Blanco telescope while astronomers were working and taking images.  In the photo below you see a number of our team, including me looking very cold.  It was warm in the control room, but I had just come in from the cold outside.  To the left, with her arm extended, is Dr. Katherina Vivas explaining in a very excited way what she was observing that night.  Dr. Vivas is a staff astronomer, and that evening she was working with her colleague, Dr. Ting Li, who you can barely see in the background seated at a control panel.


This was a night where the DECam was dedicated to projects other than the Dark Energy Survey. Drs. Vivas and Ling are studying features of the satellite galaxies that we have surrounding our Milky Way. The two largest and most well-known are the Large and Small Magellanic Clouds. They are only visible in the southern hemisphere. I was to learn that night that there are dozens more.

There were so many highlights on this trip, and that night in the control room of the Blanco was one of them.  Prior to the trip, one of the experiences I had longed for was to be in an observatory control room when astronomers were taking images. This night was it! In fact, it was the only night we had of that kind. I thoroughly enjoyed asking questions of a professional astronomer and finding out new information.

And to close this page I'd like to leave you with a final photo that represents one of the other experiences that I had longed for in coming to Chile this time. Once again I credit my colleague, Ed Ting, for this photo. Thanks, Ed! It was actually taken in the northern Atacama Desert, but as we exited the Blanco Observatory that night we came out into the star-studded sky that you see below. The southern view of our home galaxy, the Milky Way, is simply breath-taking!  I leave you with that beauty.

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

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