“A giant in life, my father leaves a gigantic void (…). by astra my dear father, the stars are lucky”. It was on his website that Nadia Drake, daughter of the famous American astronomer Frank Drake, announced the scientist’s death. He died on September 2, 2022 of natural causes at the age of 92 at his home in Aptos, California. And leaves a huge legacy in radio astronomy as well as in research aimed at discovering and communicating with possible extraterrestrial civilizations – better known by the acronym SETI (Search for Extra-Terrestrial Intelligence).
Pioneering studies in planetology
After earning a doctorate in 1955 at Harvard University, Frank Drake had landed his first position at the American Observatory of Radio Astronomy in Green Bank, West Virginia. He used this to map the center of the Milky Way. And in planetology, carried out pioneering studies on the ionosphere and magnetosphere of the gas giant Jupiter, but also on the atmosphere and the warm surface of our neighbor Venus.
Creative and very daring, Frank Drake also undertook, from the late 1950s, to use radio telescopes to detect waves produced by civilizations at a technological level comparable or more advanced than ours. While his colleagues’ attention was already focused on possible signs of life on the planet Mars, he therefore looked much further. And so in 1960 launched an observation program aimed at two stars with a mass similar to the Sun, Tau Ceti and Epsilon Eridani, located about 11 light years from Earth.
The meeting with Carl Sagan
Dubbed Ozma (from the name of the princess of the land of Oz invented by the American writer Frank Baum), this program mobilized modest financial resources, lasted only about twenty days and proved unsuccessful. But it was the first attempt to receive signals from potential extraterrestrial intelligences! Despite Frank Drake’s desire to remain discreet, to avoid criticism, she attracted the attention of the international press. Like young and brilliant scientists, among them Carl Sagan, who developed their own research into extraterrestrial intelligences and established solid collaborations.
A year later, still at Green Bank, Frank Drake worked out one of the most famous equations in astronomy and exobiology. According to this formula, which has inspired a wealth of work and speculation, both by researchers and science fiction writers, the number (N) of potentially detectable civilizations will depend fundamentally on seven multiplicative terms: the rate of star formation in Our Galaxy; the fraction of stars with planets; the fraction of planets that can support life; the part of these planets where life actually arose; the part of these planets where intelligent life appears; the fraction of these planets that are able and willing to communicate; and finally the average lifespan of a civilization. Thus, according to Frank Drake’s estimate, N would be about … a million.
Listen, but also send messages
The radio astronomer listened for extraterrestrial signals and also looked for ways to communicate. In 1972, together with Carl Sagan and his wife, he designed an aluminum plate embedded in the NASA Pioneer 10 and 11 probes: the first to explore the outer regions of the Solar System and possess the escape velocity necessary to leave it. The plate, intended to convey information about the origin of these probes, represented a pair of people, male and female, as well as the nine planets of the solar system – Pluto is still considered as such.
The plate aboard the Pioneer 10 and 11 probes. Credit NASA.
bottles in the sea
In 1974, Frank Drake used the Arecibo Telescope in Puerto Rico to send the first interstellar message using radio waves. Composed of 1679 bits of binary information, it targeted a cluster of stars located 22,000 light years from Earth. Thus, 44,000 years (the duration of a round trip signal) would be needed to receive a possible answer…
Then in 1977, again together with Carl Sagan, the American scientist supervised the production of video discs placed this time in the Voyager 1 and 2 spacecraft. They contained images of the Earth, animal noises or even greetings spoken in 55 languages … including French. Like the twin space probes, they are currently sailing about 20 and 23 billion kilometers from Earth, well beyond the material influence of the Sun. These messages were a bit like “bottles in the sea”, more symbolic than anything else. But the discs could physically survive and wander the galaxy for 4 to 5 billion years. And potentially be recovered, one day, by possible ET travelers…
The Arecibo telescope pictured in 2019, a year before it collapsed. University of Central Florida.
In addition to his various responsibilities and administrative functions, Frank Drake taught at several universities before retiring in 1996. However, he retained the position of Professor Emeritus of Astronomy and Astrophysics at the University of California. And sat almost until the end of its existence on the board of the Seti Institute, a non-profit organization whose mission is to explore and understand the origin and spread of life in the universe.