After the US government released its long-awaited report on unidentified aerial phenomena, we explore the cultural history and scientific taboo around UFOs. And three months after rebels killed the president of Chad in central Africa, we talk to experts about the balance of power there. Welcome to The Conversation Weekly.

In the end, when it finally dropped on June 25, the US government's report on unidentified aerial phenomena didn’t mention the word extraterrestrial once. And nobody had expected it to. We talk to Chris Impey, university distinguished professor of astronomy at the University of Arizona, about what it did actually say and why doing serious research into UFOs has been such a taboo for scientists. And Greg Eghigian, professor of history at Penn State University, gives us a cultural history of UFOs and how what started as an American obsession spread around the world.

And in our second story, we head to Chad in central Africa where the country's long-serving president, Idriss Déby was killed suddenly by rebels in April. Line Engbo Gissel, associate professor of global political sociology at Roskilde University in Denmark and Troels Burchall Henningsen, assistant professor at the Royal Danish Defence College, talk us about Chad's 'gatekeeper politics' and why its legacy will live on beyond Déby.

And Naomi Joseph, arts and culture editor at The Conversation in London, gives us some recommended reading. 

The Conversation Weekly is produced by Mend Mariwany and Gemma Ware, with sound design by Eloise Stevens. Our theme music is by Neeta Sarl. You can find us on Twitter @TC_Audio, on Instagram at theconversationdotcom or via email on [email protected]. You can also sign up to The Conversation’s free daily email here. Full credits for this article available here.

Further reading

Pentagon UFO report: No aliens, but government transparency and desire for better data might bring science to the UFO world, by Chris Impey, University of Arizona

The truth is still out there: why the current UFO craze may be a problem of intelligence failings, by Kyle Cunliffe, University of Salford

Pentagon report says UFOs can’t be explained, and this admission is a big deal , by Adam Dodd, The University of Queensland

UFOs: how to calculate the odds that an alien spaceship has been spotted, by Anders Sandberg, University of Oxford

Legacy of Chad’s gatekeeper politics lives on beyond Déby – and carries grave risks, by Line Engbo Gissel, Roskilde University and Troels Burchall Henningsen, Royal Danish Defence College

France’s decision to pull troops out of the Sahel invites a less military approach, by Folahanmi Aina, King's College London

China is using mythology and sci-fi to sell its space programme to the world, by Molly Silk, University of Manchester

Why this Rodin scholar would gladly see the back of The Thinker, by Natasha Ruiz-Gómez, University of Essex