Space & Physics: Mysterious comets that wander throughout the solar system

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April 17 —Hello readers, I'm covering for Lee today. This week, particle physicists are one step closer to defining the neutrino. Plus, mathematicians' favorite shapes, and a group of mysterious comets with inexplicable movements. All that and more below. Enjoy! —Andrea Gawrylewski, Chief Newsletter Editor

Top Stories

Mysterious Dark Comets Puzzle Astronomers A group of comets with unexplained movements presents a quandary Robin George Andrews

Five Key Climate and Space Projects Are on Trump's Chopping Block Leaked budget documents indicate that key NASA and NOAA research projects, such as crucial climate research and the Nancy Grace Roman Space Telescope, are at risk of being defunded in 2026 Alexandra Witze, Dan Garisto, Jeff Tollefson, Nature magazine

Fusion Energy Needs Continued U.S. Leadership to Secure Our Energy Future The U.S. leads the world in fusion energy research. It can't squander that lead like it did with microchips Tammy Ma

Content brought to you by Scientific American Travel Join Us for an Extraordinary Eclipse Experience Take an unforgettable journey to witness the 2026 total solar eclipse from a semi-private ship. Surrounded by the shimmering sea, you'll feel the collective excitement as you watch totality approach with fellow science lovers and your trip leader, Senior Editor Clara Moskowitz. Learn More.

Physicists Are Closer Than Ever to Solving the Puzzle of the Ghostly Neutrino's Mass In just the first 259 days of data collection, KATRIN, a beta-decay-based detector in Germany, has set the smallest upper limit yet on the mass of the neutrino—the universe's lightest massive particle Gayoung Lee

What Defines a Star? At the lower end, and to the bitter end, defining a star is tougher than you might expect Phil Plait

Mathematicians' Favorite Shapes Hold the Key to Big Mathematical Mysteries Mathematicians describe the most beautiful and beguiling forms and surfaces they know Rachel Crowell, Violet Frances

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What We're Reading

A rare "cannibal" coronal mass ejection on the sun hit Earth this week and created some stunning auroras. | Space.com A group of researchers propose that life gets more complex with time, which would rewrite our understanding of time and evolution. | Quanta Two U.S. senators are trying to move the Space Shuttle Discovery out of the Smithsonian. | Ars Technica

From the Archive

What Are Neutrinos, and How Can We Measure Their Mass? The weirdest subatomic particles require enormous equipment to study Joanna Thompson

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