The Arecibo Observatory. (Image courtesy UCF/Arecibo/NSF)

The Arecibo Observatory, the world’s most iconic radio dish, has reached the end of the line.

The National Science Foundation announced on Nov. 19 that the damaged observatory would be decommissioned and deconstructed. 

For more than 50 years, the 1000-foot-wide Arecibo dish was the largest single radio telescope in the world. The dish saw first light in November 1963, and now faces demolition more than 57 years later.

The trouble started back in August with the failure of one of the auxiliary cables that suspends the 900-ton receiving platform nearly 500-feet above the surface of the dish. As engineers were planning repairs, another cable snapped on Nov. 6, further damaging the observatory.

Three independent engineering teams determined that the chances of saving the observatory safely were slim, so the decision was made to decommission Arecibo.

The giant dish was built in the cavity formed by a natural sinkhole in the hills of Puerto Rico. The observatory was the most powerful and sensitive radar dish in the world and an extremely sensitive radio receiver.

Radio waves are a form of electromagnetic radiation, just like visible light. Radio light has wavelengths from just under a millimeter to more than 100 kilometers while visible light has wavelengths from 380 to 700 billionths of a meter. 

The loss to the scientific community and to Puerto Rico cannot be overstated. 

No other instrument can do what Arecibo did. The observatory’s capabilities ranged from imaging galaxies and determining the chemical composition of distant molecular clouds, to using its radar to image near Earth asteroids and even other planets in our solar system. 

Using Arecibo’s radar, we determined the rotation period of Mercury and measured the distance to other planets with incredible accuracy. The observatory provided the first solid evidence for the existence of neutron stars and discovered the pulsar around which the first extrasolar planets were discovered. 

In addition to its many observations and discoveries, the massive dish has appeared in many popular films and was a symbol of the scientific progress of humanity. We also used it to send a message toward the Great Globular Cluster in Hercules back in 1974. If intelligent life exists anywhere within that cluster, we should be getting a response in about 49,954 years.  

The Weekly Roundup: The Morning Sky

Venus continues to dominate the early morning eastern sky. Mercury is still visible very low in the east before dawn. M13, the Great Globular Cluster in Hercules, is about as high as Venus in the north eastern sky. Use binoculars to spot this collection of several hundred thousand stars as it appeared 25,000 years ago. 

The Evening Sky

Mars has dimmed a bit since opposition, but it is still an unmistakable reddish-orange jewel high in the east as darkness falls. Jupiter and Saturn continue to shine in the south west after sunset. These two giant worlds are inching closer together over the coming weeks, culminating in a spectacular conjunction on Dec. 21. Binoculars allow you to see a couple of the biggest moons of Jupiter.  

Thanksgiving means two more nights we can stay up late to observe the night sky. Thanksgiving is also the perfect time for me to say “thank you” to everyone who reads this column. 

Dan Price is a NASA/JPL Solar System Ambassador and informal educator. He leads the Night Sky Tours at Josephine Sculpture Park. Have a question about astronomy or space science? Send an email to dan@starpointestudio.com and it might be featured in a future column.

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