Our mission is to inform, educate and entertain by providing a varied and interesting program of activities for our membership and the communities we serve.  Our projects include educational programs and presentations by guest speakers and our members, public star parties, field observation of various astronomical events and trips to observatories and other space science venues. If you are as interested in Astronomy as we are, we hope you will join us at one of our star parties, meetings, or lectures. If you would like to become a member please click HERE.

Membership is open to anyone with an interest in astronomy; no equipment required.

By Jim Feiste

On November 16, 1974, at exactly 1pm, a single tone suddenly split the air of the northern Puerto Rico rainforest. This tone was followed by a series of rapidly alternating musical tones that lasted for a full 3 minutes.  Then another single tone again.  Then silence.

Was it aliens? Descriptions of this event remind me of the iconic final scene of the movie Close Encounters of the Third Kind. But this time the sounds were distinctly terrestrial. They were radio transmissions beamed into deep space towards the globular cluster M13. 

The Arecibo Message 

The Arecibo Observatory is a huge, 1000-foot radio telescope located on top of a mountain in Arecibo, Puerto Rico.  It is the large bowl-shaped antenna featured in James Bond’s Goldeneye, Carl Sagan’s Contact, and even the X-Files. The observatory began operations in 1962, but in 1974 it was shut down for an upgrade.

For its grand-reopening, scientist at Arecibo thought a demonstration of their new high powered transmitter was in order.  And what better to send a signal to aliens!  For this they enlisted the help of astronomers Frank Drake and Carl Sagan.

First: Where to send it?  A globular cluster like M13 seemed like a good choice. Scientists have speculated that globular clusters might support advanced civilizations due to the sheer number of stars in close proximity to each other.  More stars means more planets where life could arise; and close proximately means easier interstellar travel to build advance civilizations. M13 is a huge globular cluster (Click Here) containing over 300,000 closely placed stars. It is also fairly near the earth in astronomical terms - 25,000 lightyears - and nearly straight above us in the Milky Way Galaxy (Click Here). One signal could reach a lot of alien ears!

But the real reason for choosing M13 was far more mundane. Arecibo’s antenna can only look straight up. It just so happened that at 1pm on the day of the opening, M13 was directly overhead!

Next: How do you talk to an alien civilization that look and talk nothing like us?  (Bear with me: this gets technical, but it’s truly fascinating!) Assuming the civilization is advanced enough to have radio telescopes to receive the message, it stands to reason they understand mathematics of prime numbers (numbers only divisible by 1 and itself) and binary signals (the basis of modern digital tech).

With this in mind, Drake devised a binary set of images that could be carried on radio waves broadcast towards M13.  The radio signal beams out from the antenna at 2380 megahertz (that’s a lot).  By shifting the signal strength down by 10 hertz 10 times every second, it creates a morse code-like signal.  An advanced civilization would recognize that this is not a random sequence and investigate further.

A total of 1679 bits were broadcast.  This number was chosen because it is “semi-prime” number, divisible by 23 and 73. In effect, this instructs the receiver to lay the message out in a grid of 23 columns and 73 rows to form a “readable” picture (Click Here).

The message describes our number system, our biochemistry, our size and location, and - in a bit of audacious self-advertising - a picture of the Arecibo Observatory.   Drake sent the message to other scientists without explanation, and they were able to decipher it fairly quickly.

Unfortunately, given the distance to M13, it will take 25,000 years to get there, and another 25,000 years to get a reply.  Worse yet, since M13 orbits the Milky Way, it will have moved away by then; so the message will never actually get there.  It was more of a demo than a serious call.

Messier 13

This month you can find Messier 13 (a/k/a NGC 6205 or the “Great Hercules Cluster”) by facing WEST and locating the “keystone” shape of Hercules (Click Here). In dark skies, M13 appears as a fuzzy star to the naked eye, and a hazy orb with a bright center in binoculars.  In larger scopes and Stan’s Photo (Click Here), you can see thousands of tightly grouped stars. Perhaps there are planets around these stars… with people… just waiting for a message from us!

Our member submission for the month of September is an astrograph of M13 by Stan Smith. Click here for more member submissions.

Public meetings are cancelled until further notice. 

CAAA has been a NASA Night Sky Network member since 2004. The Night Sky Network(NSN) is a nationwide coalition of amateur astronomy clubs bringing the science, technology, and inspiration of NASA's missions to the general public.