A Green Flash from the Sun
4.06.2014

Many think it is just a myth. Others think it is true but its cause isn't known. Adventurers pride themselves on having seen it. It's a green flash from the Sun. The truth is the green flash does exist and its cause is well understood.

Firefall by Moonlight
8.06.2017

On certain dates in February, an elusive firefall can be spotted at sunset in Yosemite National Park, when the weather cooperates and the direction to the setting Sun is just right. Often photographed from...

Road to the Galactic Center
25.10.2021

Does the road to our galaxy's center go through Monument Valley? It doesn't have to, but if your road does -- take a picture. In this case, the road is US Route 163 and iconic buttes on the Navajo National Reservation populate the horizon.

Planetary Alignment over Italy
19.12.2021

It is not a coincidence that planets line up. That's because all of the planets orbit the Sun in (nearly) a single sheet called the plane of the ecliptic. When viewed from inside that plane -- as Earth dwellers are likely to do -- the planets all appear confined to a single band.

APOD: 2023 March 27 Б Aurora Over Arctic Henge
27.03.2023

Reports of powerful solar flares started a seven-hour quest north to capture modern monuments against an aurora-filled sky. The peaks of iconic Arctic Henge in Raufarhцfn in northern Iceland were already aligned with the stars: some are lined up toward the exact north from one side and toward exact south from the other.

Southwest Mercury
13.02.2000

The planet Mercury resembles a moon. Mercury's old surface is heavily cratered like many moons. Mercury is larger than most moons but smaller than Jupiter's moon Ganymede and Saturn's moon Titan. Mercury is much denser and more massive than any moon, though, because it is made mostly of iron.

A Triangular Shadow of a Large Volcano
5.07.2011

Why does the shadow of this volcano look like a triangle? The Mount Teide volcano itself does not have the strictly pyramidal shape that its geometric shadow might suggest. The triangle shadow phenomena is not unique to the Mt. Teide, though, and is commonly seen from the tops of other large mountains and volcanoes.

A Blue Blood Moon
3.10.2015

This sharp telescopic snapshot caught late September's Harvest Moon completely immersed in Earth's dark umbral shadow, at the beginning of a total lunar eclipse. It was the final eclipse in a tetrad, a string of four consecutive total lunar eclipses.

South Celestial Rocket Launch
28.02.2020

At sunset on December 6 a Rocket Lab Electron rocket was launched from a rotating planet. With multiple small satellites on board it departed on a mission to low Earth orbit dubbed Running Out of Fingers from Mahia Peninsula on New Zealand's north island.

Three Planets and a Comet
23.12.2021

Are you still looking for that perfect holiday gift for an astronomer? If your night sky is dark and horizon clear enough, the Solar System may have done your shopping for you. Send them outside after sunset to see three planets and a comet.