“Hello, Earth. Guyanautes here.”

On Monday mornings, the voices of Guyane Astronomie can be heard by anyone tuned to Radio Péyi, a local station in French Guiana. Every week, the devoted group of astronomers and star lovers broadcast a fictional transmission from an imagined future in which “Guyanautes” recount stories of the stars, the skies, and their home country: French Guiana, a small nation on the northern tip of South America.

This remote European territory between Suriname and Brazil is primarily known within the space and scientific community for being the home of Centre Spatial Guyanais, Europe’s spaceport. Since its installment in the 1960s, Kourou is renowned for the launch of the very reliable, albeit now retired, Ariane 5 rocket and its predecessors. In our previous dispatch from the region, we looked back a hundred years, when the French government shipped thousands of prisoners to the territory to live in exile and be forced into hard labor. Many dying from the conditions. And how, within two decades, this “green hell” transformed into a technological and scientific center.

This time, we tag along with the Guyanautes as the radio program explores the late 1600s, when French Guiana was home to a consequential astronomical event that laid the basis for some of the century's most remarkable scientific findings.

At this point in history, French Guiana was a volatile and violent place as several colonial powers and Amerindian groups fought for control over the territory, largely covered by the Amazonian rainforest. These astronomical discoveries occurred in a time when Amerindian and slave communities deeply suffered from colonial oppression by imperial powers. It's important to note that scientific endeavors were largely driven, and made possible, by this colonial rule. Missions relied heavily upon the ease of movement for Europeans at a time when they possessed much of the world.

In the midsts of these conflicts, Jean Richer, a French astronomer, and his work companion Meurisse (last name unknown) set sail to the then-French colony in early 1672 to answer one of the most pertinent astronomical queries of that time: what is the distance between the Sun and Earth?

The fall of that year would be a prime moment for measurements, as Mars would stand the closest to Earth in more than a decade. The French Académie Royale des Sciences sent the pair to the equator (French Guiana lies at 5 degrees North, a key reason why it was chosen as a launch site centuries later) such that they and a compatriot in Paris could make simultaneous observations of Mars. The voyage across the Atlantic alone took the pair more than a month, only to be welcomed by the harsh conditions of the South American rain season.

In this mostly-unexplored territory, Richer had to be perseverant and resourceful to build the observatory necessary for their task. They managed to do so in a span of a few months and as the skies cleared with the arrival of the dry season, Richer stared at the night sky for weeks, noting down his observations and conducting measurements. The report he wrote afterwards was shared with his research partner in Paris and would come to play an important role in modern astronomy. 

So, who is this famous astronomer who had stayed behind to conduct the measurements in the (relatively) safe confines of Paris? His name: Giovanni Cassini. By computing the parallax, which is the observed displacement of an object caused by the change of the observer's point of view, Cassini used Richer's observations as well as his own to come to the estimation that the Earth and Sun are 138 million kilometers apart. An estimation so close to what we now know (150 million kilometers) that he is applauded for it to this day. He is the namesake of the famous Cassini probe sent to explore Saturn, known for the image “the day earth smiled” as well as its many scientific discoveries.

But whereas Cassini is still acclaimed centuries on, Richer, and his trip to French Guiana largely disappeared from our collective memory.

Guyane Astronomie is fighting to change this. They organize events throughout the territory to promote astronomy and its historical roots in French Guiana, including stargazing evenings, astronomy talks, and four conferences per year. Additionally, they advocate for a more widespread understanding of the astronomical practices of the many Amerindian communities in French Guiana, for whom the stars are guides to maintaining an agricultural calendar.

Supercluster spoke to Gaetan, one of the key members of the organization, and he showed us an excerpt from French Astronomer Aymar de la Baume Pluvinel, who visited French Guiana a century after Richer did. Avid amateur astronomer and solar eclipse chaser, Pluvinel led an expedition in 1899 to witness Richer's astronomical event. The experience left such an impression that he wrote a year later: "I hope that French Guiana will still play a role in the story of science, and I hope that a new astronomical phenomenon will bring me back to Cayenne where they know how to welcome astronomers so well."

Today, French Guiana still plays a critical role in amplifying astronomical knowledge of the universe. On Christmas morning in 2021, French Guiana saw the James Web Space Telescope (JWST) launched from Kourou, taking less time to reach its destination than the Atlantic crossing took Richer and Meurisse. From there, JWST has sent countless images of the universe back to Earth dazzling the general public with new science and stunning glimpses into the universe. In April of 2023, JUICE (Jupiter Icy Moon Explorer) set off from the same location, on a quest to find out if the moons around Jupiter hold secrets about the origin of life. With flagship exploration missions like these, French Guiana plays a huge role in the global scientific community that could have hardly been imagined by the researchers that made their way here centuries ago.

It is the JWST launch that birthed Guyane Astronomie. The club is now run by 7 enthusiastic, mainly amateur, astronomers, who organize a monthly star gazing session for its 70 or so members. The Guyanautes radio program is an initiative by its vice-president, Frédéric, with Gaetan’s support. They hope to reach as many locals as possible, which can be a challenge when certain locations are only accessible by spending days on a boat traversing the Amazon. “We hope to inspire the passionate and the amateurs, those who want to help the development of our events and actions,” said Gaetan.  

Their latest project is to launch astro-tourism in French Guiana to share the wealth of stories and experiences that this oftentimes overlooked territory has to offer. The Guyanautes, and Guyane Astronomie at large, make sure that the astronomical potential, and past, of French Guiana, are not forgotten.