Equinox: Analemma over the Callanish Stones
22.09.2018

Does the Sun return to the same spot on the sky every day at the same time? No. A more visual answer to that question is an analemma, a composite image taken from the same spot at the same time over the course of a year.

Aurora Over Yellowknife
22.09.2009

Sometimes, after your eyes adapt to the dark, a spectacular sky appears. In this case, a picturesque lake lies in front of you, beautiful green auroras flap high above you, brilliant stars shine far in the distance, and a brilliant moon shines just ahead of you.

APOD: 2026 April 16 Б South Celestial Tree
15.04.2026

If you live in the northern hemisphere, you may have learned how to locate the North Star, Polaris, in the night sky. It can be used to find north, and it approximately marks the northern celestial pole.

MAVEN s Ultraviolet Mars
26.06.2023

These two global views of Mars were captured at ultraviolet wavelengths, beyond the spectrum visible to human eyes. Recorded by the MAVEN spacecraft's Imaging Ultraviolet Spectrograph instrument in July 2022 (left) and January 2023, three otherwise invisible ultraviolet bands are mapped into red, green, and blue colors.

Solstice Sun and Milky Way
20.12.2017

Welcome to December's solstice, first day of winter in the north and summer for the southern hemisphere. Astronomical markers of the seasons, solstice and equinox dates are based on the Sun's place in its annual journey along the ecliptic, through planet Earth's sky.

APOD: 2025 April 29 Б Saturns Rings Appear to Disappear
28.04.2025

Where are Saturn's ears? Galileo is credited, in 1610, as the first person to see Saturn's rings. Testing out Lipperhey's recently co-invented telescope, Galileo did not know what they were and so called them "ears". The mystery deepened in 1612, when Saturn's ears mysteriously disappeared.

Moons Beyond the Rings of Saturn
12.07.2010

What's happened to that moon of Saturn? Nothing -- Saturn's moon Rhea is just partly hidden behind Saturn's rings. In April, the robotic Cassini spacecraft now orbiting Saturn took this narrow-angle view looking across the Solar System's most famous rings.

Seasonal Streaks Point to Recent Flowing Water on Mars
29.09.2015

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...

A Phoenix Aurora over Iceland
2.01.2021

All of the other aurora watchers had gone home. By 3:30 am in Iceland, on a quiet September night, much of that night's auroras had died down. Suddenly, unexpectedly, a new burst of particles streamed down from space, lighting up the Earth's atmosphere once again.

Hubble Holiday
23.12.1999

How would you like to spend your holiday in low earth orbit? That's what the crew of the space shuttle Discovery is doing as they deliver six new gyros and a faster main computer to the orbiting Hubble Space Telescope.