Three Tails of Comet NEOWISE
8.03.2021

What created the unusual red tail in Comet NEOWISE? Sodium. A spectacular sight back in the summer of 2020, Comet NEOWISE, at times, displayed something more than just a surprisingly striated white dust tail and a pleasingly patchy blue ion tail.

A Radar View of Titan
24.11.2004

Where are Titan's craters? Throughout our Solar System's five billion-year history, dangerous rocks and chunks of ice have continually slammed into planets and moons - usually creating numerous long lasting impact craters. When the robot spacecraft Cassini swooped past Saturn's moon Titan last month, however, radar images showed few craters.

Flyby Image of Saturns Sponge Moon Hyperion
3.06.2015

Why does this moon look like a sponge? To better investigate, NASA and ESA sent the Saturn-orbiting robotic spacecraft Cassini zooming past Saturn's moon Hyperion, once again, earlier this week. One of the images beamed back to Earth is featured above, raw and unprocessed.

The Space Station Crosses a Spotless Sun
15.07.2019

That's no sunspot. It's the International Space Station (ISS) caught passing in front of the Sun. Sunspots, individually, have a dark central umbra, a lighter surrounding penumbra, and no solar panels. By contrast, the ISS is a complex and multi-spired mechanism, one of the largest and most sophisticated machines ever created by humanity.

A Slow Explosion
25.03.2003

Why would a gamma ray burst fade so slowly? This behavior, recorded last October, is considered a new clue into the cause of gamma-ray bursts, the most powerful explosions known in the universe.

Haumea of the Outer Solar System
23.09.2008

One of the strangest objects in the outer Solar System was classified as a dwarf planet last week and given the name Haumea. This designation makes Haumea the fifth designated dwarf planet after Pluto, Ceres, Eris, and Makemake. Haumea's smooth but oblong shape make it extremely unusual.

Collapse in Hebes Chasma on Mars
12.08.2014

What's happened in Hebes Chasma on Mars? Hebes Chasma is a depression just north of the enormous Valles Marineris canyon. Since the depression is unconnected to other surface features, it is unclear where the internal material went.

Seasonal Streaks Point to Recent Flowing Water on Mars
30.09.2015

What creates these changing streaks on Mars? Called Recurring Slope Linea (RSL), these dark features start on the slopes of hills and craters but don't usually extend to the bottom. What's even...

APOD: 2025 August 31 Б NGC 7027: The Pillow Planetary Nebula
31.08.2025

What created this unusual planetary nebula? Dubbed the Pillow Nebula and the Flying Carpet Nebula, NGC 7027 is one of the smallest, brightest, and most unusually shaped planetary nebulas known. Given its expansion rate, NGC 7027 first started expanding, as visible from Earth, about 600 years ago.

Doomed Star Eta Carinae
28.11.2004

Eta Carinae may be about to explode. But no one knows when - it may be next year, it may be one million years from now. Eta Carinae's mass - about 100 times greater than our Sun - makes it an excellent candidate for a full blown supernova.