ALMA – Not a Typical Telescope

The Atacama desert is the driest and highest in the world, and that’s one of the main reasons that we built “ALMA,”* the largest radio telescope in the world here! I say “we” because it was an international collaboration – an example of us humans working together to better understand the universe in which we live.

“The purpose of ALMA is to study star formation, molecular clouds and the early Universe, closing in on its main objective: discovering our cosmic origins.”

To most of us, a telescope is an apparatus of lenses pointed at the sky to see stars, (or far away visible light in the sky). But the ALMA telescope is not one, but 66 antenas pointed at the sky! Just like we have 2 eyes that give us a single image of the world, the telescope has 66 eyes to give us a single image – it’s like a mom that has eyes in the back of its head. Or like a fisheye camera.

The other unique thing about the ALMA telescope is that it isn’t viewing light in space like an optical telescope, it’s looking at the dark and cold part of space, capturing radio waves* emitted by stars and planets.

One of the antenas undergoing maintenance

That doesn’t mean that stars and planets are broadcasting songs. Radio waves are emitted by the cold and cool matter in the universe that doesn’t give off light and so can’t be seen with our eyes (or with optical telescopes). But the ALMA telescope can receive these signals and tell us about that matter out there in space.

For example, the ALMA telescope was able to detect sugar molecules around a young sun, indicating a good possibility for a life-supporting planet to develop in that solar system.**

In some cases, scientists can combine the information from an optical telescope and ALMA (and x-ray and infrared telescopes)* to give a fuller picture of a solar system or galaxy, and to “see” what’s happening in the dark spots of the sky.

Also, since it’s not optic, ALMA can point at the sun and study the sun’s atmosphere without burning.

For me, one of the most interesting abilities it has is to study the early universe – it has found evidence of the earliest known solar system – suns that formed just 250 million years after the Big Bang. (Sounds like a long time, but it’s only 2% of the universe’s current age, which is about 13.8 billion years.)

I know, this is a lot of high tech modern science stuff. But according to our guide, the basic principle behind the antena design is actually something that was used hundreds of years ago by the pre-Incan culture, the Tihuanacu.

Just outside of La Paz, you can visit an archeological site of the Tijuanacu. Then you can head a thousand miles south to the ALMA observatory in northern Chile to see the modern day use of this technology studying the origins of the universe!

While the tour to the observatory is free, it takes a bit of luck to get there. To be on the official list you have to reserve online, usually 6 months to a year in advance. If you don’t make the official list, you might be able to get on the online waitlist. But since the list fills up so far in advance, a lot of people on the list end up not making it on the dates they reserved. So you still have a chance to get on the “hope list” the day of the tour. The bus leaves at 9am, but people show up sometimes 2 hours early to wait in line to be on the “hope list”. If there are any empty spaces from people who didn’t show up from online reservations, next priority goes to the wait list and then to the hope list, in order of arrival. It makes it that much more exciting to get chosen from the hope list! It’s like winning the lottery!

Famous Footnotes

*The ALMA – Atacama Large Millimeter/submillimeter Array – captures electromagnetic radiation with wavelengths in the range of milimeter wavelenths in the electromagnetic spectrum.

(There are also other non optical telescopes that exist- infrared and X-ray telescopes that capture information from other non visible light parts of the electromagnetic spectrum.)


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