Sun Pillar with Upper Tangent Arc
17.02.2021

This was not a typical sun pillar. Just after sunrise two weeks ago in Providence, Rhode Island, USA, a photographer, looking out his window, was suddenly awestruck. The astonishment was caused by a sun pillar that fanned out at the top.

A Supercell Thunderstorm Over Texas
13.06.2021

Is that a cloud or an alien spaceship? It's an unusual and sometimes dangerous type of thunderstorm cloud called a supercell. Supercells may spawn damaging tornados, hail, downbursts of air, or drenching rain. Or they may just look impressive.

Colorful Airglow Bands Surround Milky Way
13.03.2022

Why would the sky glow like a giant repeating rainbow? Airglow. Now air glows all of the time, but it is usually hard to see. A disturbance however -- like an approaching storm -- may cause noticeable rippling in the Earth's atmosphere.

APOD: 2025 March 16 Б Venus and the Triply Ultraviolet Sun
16.03.2025

This was a very unusual type of solar eclipse. Typically, it is the Earth's Moon that eclipses the Sun. In 2012, though, the planet Venus took a turn. Like a solar eclipse by the Moon, the phase of Venus became a continually thinner crescent as Venus became increasingly better aligned with the Sun.

The Hubble Deep Field South
14.12.1998

Among the faintest objects are some of the most unusual objects. The Hubble Deep Field South was released after much anticipation earlier this month, delivering a unique view of some of the most distant parts of our universe. Part of this field is shown above.

Resolving Mira
21.01.2001

Most stars appear only as points of light. In 1995, Betelgeuse became the second star, after our Sun, to have it surface resolved. Later that year, Mira was added to the list. Mira...

A Sonic Boom
21.02.2001

Many people have heard a sonic boom, but few have seen one. When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane.

Mercury on the Horizon
12.04.2003

Have you ever seen the planet Mercury? Because Mercury orbits so close to the Sun, it never wanders far from the Sun in Earth's sky. If trailing the Sun, Mercury will be visible low on the horizon for only a short while before sunset.

Humphrey Rock Indicates Ancient Martian Water
10.03.2004

How prevalent was water on Mars? Results from the Spirit rover now indicate that Gusev crater likely had a wet past, a result that comes shortly after Spirit's twin rover Opportunity uncovered clear evidence of past water at Meridiani Planum on the other side of Mars.

Prometheus Creating Saturn Ring Streamers
2.08.2010

What's causing those strange dark streaks in the rings of Saturn? Prometheus. Specifically, an orbital dance involving Saturn's moon Prometheus keeps creating unusual light and dark streamers in the F-Ring of Saturn. Now Prometheus orbits Saturn just inside the thin F-ring, but ventures into its inner edge about every 15 hours.