SUNSET: 
How Did Pluto's Moons Form?
A massive collision with Pluto’s moon Charon could have formed the dwarf planet’s collection of smaller moons.
Close Encounters in the Milky Way — and What They Mean for Planets
New research shows stellar flybys are common in our galaxy’s crowded center. That could have both good and bad (but mostly bad) effects on growing planets.
Weak Martian Magnetic Field May Have Let Air Out
Mars's magnetic field weakened and disappeared billions of years ago. Now, scientists have found that the weak field might have been worse than none at all.
Is Earth's Minimoon Still Here?
Reports of the loss of Earth's minimoon may have been somewhat exaggerated — new research suggests the moonlet will leave Earth orbit in early may.
Flapping "Bat Wing" Could Reveal Secrets of Planet Formation
The shadow cast by a protoplanetary disk takes the shape of a bat — and over time, flaps like one, too. The eery shadow could help astronomers understand the planet-forming material inside the disk.
New Horizons Flyby Target Receives Official Name: Arrokoth
When NASA's New Horizons flew by a distant Kuiper Belt Object on New Year's Day, they nicknamed it "Ultima Thule." Now, the object has received an official moniker: Arrokoth.
Interstellar Comet Borisov "Indistinguishable" from Solar System Comets
The solar system's newest interstellar visitor, Comet 2I/Borisov, bears a striking resemblance to the icy population of the outer solar system.
Teens Hunt for Meteorites . . . Underwater
Students and a sled named Starfall are on the hunt for underwater meteorites, dropped as a bolide fragmented over Lake Michigan last year.
Paintballs Clarify What Happens When an Asteroid Hits Earth’s Ocean
Coastal waves from mid-sized asteroid impacts might be more like a storm surge than a wall of watery destruction, according to NASA experiments with paintballs.
Potential Trouble for Life on Icy Moons
A lack of dry land on moons such as Europa and Enceladus might make it difficult to seed oceans with phosphorus, an element essential for life as we know it.
11-year-old Astronomer Shines at AAS Meeting
Cannan Huey-You, just 11 years old, impressed professional astronomers this week with his research on a massive intergalactic gas cloud.