The thing about astronomy is, once you’re into it you become addicted to the utter ginormousness of it all. I guess it’s a natural thing, considering the vastness of our universe. There are amateur astronomers with 40” telescopes, maybe bigger, and guess what, yeah, they want bigger. Astronomers have what I call an aperture jones. Give them big, they want bigger.
The quest for big, bigger, and biggest telescopes comes from our need to see, to study things out there that are either small or unimaginably far away. It’s about resolution. It takes fine resolution to see detail in something light years away. Bigger aperture = better resolution. For example, the Hubble telescope, at about 100” diameter, can just make out 1200-mile diameter Pluto, 2.8 billion miles away (about 1/2000 light year). A 200” aperture telescope would resolve Pluto into a disk with surface shading differences.
Then we came up with radio telescopes. Radio telescopes read longer wavelengths of light than visible light. The reason to do this is because long wavelengths are not bothered by interstellar dust or atmospheric clouds. The downside, because they read long wavelengths radio telescopes have to be much larger than optical telescopes to even approach similar resolution.
Aperture envy lives on with radio telescopes too! The earliest ones were five to ten feet in size and could barely discern the strongest signals. In 1963 a monster radio telescope was constructed in Puerto Rico. It was a dish 300 feet across, as big as a football field and situated in a gigantic karst sinkhole! Imagine the satellite TV reception! The builders named it Arecibo for the city it was in, named after its indigenous people’s (Taino) chief. Arecibo served the astronomy community, SETI (Search for Extra-Terrestrial Intelligence), and NASA’s Near-Earth Object discovery program. It even had a role in popular culture, appearing in the movies Contact and Golden Eye, and the TV series The X-Files.
Arecibo could also transmit signals and in 1974 astronomers used Arecibo to send a message toward globular cluster M13, letting anyone there know we are here. It’ll take about ten thousand years to reach M13.
Some of Arecibo’s achievements: Determining Mercury’s true rotation period. Mapping the distribution of ice in Mercury’s polar regions. First to directly image a Near-Earth asteroid. The existence of neutron stars, pulsars, binary pulsars and millisecond pulsars. The detection of prebiotic methylene imine and hydrogen cyanide in a distant starburst galaxy
Unfortunately, wear and tear, funding reductions, and recent hurricane damage did it in. It is too unstable to consider repairs, which would be dangerous and costly, so it is up for decommission. Arecibo had a good run.
What’s in the Sky?
November 30; 1:30 to 5:30am CST; southeast to south: Lunar penumbral eclipse. Mid-eclipse at around 3:30am. This is a challenge as the penumbra is a very light shadow.
December 4; dusk; southwest: Jupiter and Saturn getting ever closer!