Recently, a group of scientists studying the Milky Way through the world’s largest ground-based radio telescope identified something they had never seen—a cold, dense gas that had been ejected at high speed from the galaxy’s center. The mystery of this gas—what caused it, how it could move so fast, and where it will end up—prompted research by Enrico Di Teodoro, a scientist in the department of astrophysics at Johns Hopkins University. He joined Science Friday producer Katie Feather to talk about the new discovery, as well as answer some fundamental questions about what is happening at the center of our galaxy. Plus, this year, back-to-school season comes with some major challenges to keeping students and teachers safe. Recently, New York City Mayor Bill DeBlasio announced a plan to give K-12 classes the option to move outdoors; the idea is that an open space, with a fresh breeze, lessens the chance of spreading the coronavirus. We’ve been brain-storming, too: What if you could bring the benefits of the outdoors inside, by creating better ventilation in the classrooms, akin to outside winds? What would it take to re-design or modify a typical classroom—not to mention your office building or home? Most modern buildings ventilate space with 80% recycled indoor air, and 20% of fresh outdoor air, to save on energy costs. But Shelly Miller, professor of mechanical engineering at University of Colorado, Boulder says, “In a pandemic, we don’t care about energy efficiency.” Miller explains that to lower the risk of infection, ideally indoor spaces would be ventilated with 100% outdoor air—but most building HVAC systems aren’t strong enough to handle that. Miller joins Jose-Luis Jimenez, professor in the department of chemistry and biochemistry at University of Colorado, Boulder to discuss what we know about the coronavirus, and our indoor air space and how we could build safer, healthier indoor spaces for the future. And cancer immunotherapy, especially a type known as checkpoint inhibitors, has given new hope to many people with cancer. The treatment takes the brakes off the body’s own immune system, allowing it to attack tumor cells. But some people respond to the therapy, while others don’t—and it’s not entirely clear why. In recent years, researchers have been looking into the microbiome—the collection of microorganisms that live in and on your body—for clues. Studies have found that there’s a microbial difference between people who respond to immunotherapy, and those who don’t. Research recently published in the academic journal Science, suggests scientists may have finally unraveled how one of those bacteria has an effect. The researchers discovered that Bifidobacterium pseudolongum, a species of bacteria found in elevated levels in the tumors of mice who responded well to immunotherapy, produces a small molecule called inosine—and that under the right conditions, inosine can help to turn on the immune T cells needed to attack a cancerous tumor. Kathy McCoy, one of the authors of the study, and the director of the IMC Germ-Free Program at the University of Calgary, joins Ira to talk about the study, and the challenges of raising mice without any microbiome at all.