November 1 – Holy Guacamole!

Today’s factismal: The world’s largest single aperture telescope is in Puerto Rico.

Quick! What’s big enough to hold 10,000 gallons of guacamole, deep enough to put a submarine in, precise enough to see supernovae 44 million light years away, and turns fifty years old today? It is the Arecibo National Astronomy and Ionosphere Center (the Arecibo Observatory, or just Arecibo, for short).

The Arecibo "dish", big enough for a submarine to hide in (Image courtesy NAIC)

The Arecibo “dish”, big enough for a submarine to hide in
(Image courtesy NAIC)

Back in the late 1950s, scientists were just learning about the ionosphere and wanted to develop a tool that would allow them to probe its secrets. And other scientists were learning about radio emissions from planets and stars, and wanted a tool to learn about those. And when the first group of wonks met the second group of wonks, a new telescope was born.

The idea was simple: because the same energy (radio waves) that is used to probe the ionosphere is also used to learn more about distant planets and stars, instead of building two small instruments, why not build one huge one? They would get better resolution (thanks to the size of the reflecting dish), more power (thanks to the size of the transmitter/receiver), and more funding (thanks to the size of the project). And so they started looking for a place to build the world’s biggest (single aperture) telescope.

The remains of the very first supernova ever recorded (Image courtesy NASA)

The remains of the very first supernova ever recorded
(Image courtesy NASA)

They had quite a few requirements on the location. It had to be in the US (thanks to the Cold War). It had to be near the equator (so it could see the planets). It had to be in an area with eroded limestone features called karst (so that it would be easy to build). And the spot that best fit was a little place called Arecibo on the island of Puerto Rico. So that’s where they built it and, on November 1, 1963, they started getting signals.

An image of the Crab Nebula at radio frequencies (Image courtesy NASA)

An image of the Crab Nebula at radio frequencies (Image courtesy NASA)

And what amazing things they saw! At the end of six months, they had discovered that Mercury wasn’t tidally-locked to the Sun like the Moon is to Earth; instead, it had a funny 3:2 rotation so that the day on Mercury appears to take two years! Soon they proved the existence of neutron stars, and mapped asteroids, and found complex molecules in outer space. But they weren’t limited to discovering things; they could also help things discover us. On November 16, 1974, Carl Sagan and friends took over Arecibo and used it to send a message to the stars, letting ET know where to phone.

Jupiter at radio wavelengths (Image courtesy NASA)

Jupiter at radio wavelengths (Image courtesy NASA)

Arecibo continues its mission of discovery today. Though there are now larger telescopes made by linking several small telescopes together, it remains the largest single aperture telescope in the world and one of the most active telescopes, period. Twenty-four hours a day, 365.25 days a year, the astronomers at Arecibo are looking for the unusual, the beautiful, and the strange – all the normal facets of our wonderful universe. If you’d like to make a tour of that universe, then why not head over to WorldWide Telescope Ambassadors? They’ve got free web tools that allow you to create and share a trip through the most amazing parts of the sky:
https://wwtambassadors.org/wwt/

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