APOD: 2023 January 4 Б CG4: The Globule and the Galaxy
4.01.2023

Can a gas cloud eat a galaxy? It's not even close. The "claw" of this odd looking "creature" in the featured photo is a gas cloud known as a cometary globule. This globule, however, has ruptured. Cometary globules are typically characterized by dusty heads and elongated tails.

APOD: 2023 November 5 Б Creature Aurora Over Norway
5.11.2023

It was Halloween and the sky looked like a creature. Exactly which creature, the astrophotographer was unsure (but possibly you can suggest one). Exactly what caused this eerie apparition in 2013 was sure: one of the best auroral displays that year. This spectacular aurora had an unusually high degree of detail.

APOD: 2024 July 14 Б Meteor Misses Galaxy
14.07.2024

The galaxy was never in danger. For one thing, the Triangulum galaxy (M33), pictured, is much bigger than the tiny grain of rock at the head of the meteor. For another, the galaxy is much farther away -- in this instance 3 million light years as opposed to only about 0.0003 light seconds.

APOD: 2020 August 24 Б Crescent Moon HDR
24.08.2020

How come the crescent Moon doesn't look like this? For one reason, because your eyes can't simultaneously discern bright and dark regions like this. Called earthshine or the da Vinci glow...

APOD: 2023 February 28 Б Crescent Moon Beyond Greek Temple
28.02.2023

Why is a thin crescent moon never seen far from a horizon? Because the only geometry that gives a thin crescent lunar phase occurs when the Moon appears close to the Sun in the sky.

APOD: 2024 September 22 Б Chicagohenge: Equinox in an Aligned City
22.09.2024

Chicago, in a way, is like a modern Stonehenge. The way is east to west, and the time is today. Today, and every equinox, the Sun will set exactly to the west, everywhere on Earth.

APOD: 2023 November 29 Б A Landspout Tornado over Kansas
29.11.2023

Could there be a tornado inside another tornado? In general, no. OK, but could there be a tornado inside a wider dust devil? No again, for one reason because tornados comes down from the sky, but dust devils rise up from the ground.

APOD is Five Years Old Today
16.06.2000

Welcome to the sixth year of Astronomy Picture of the Day (APOD)! Above are the industrious Robert Nemiroff (left) and persistent Jerry Bonnell (right), still engaged in creating the APOD web pages. As suggested...

APOD: 2024 May 30 Б A Lunar Corona over Paris
30.05.2024

Why does a cloudy moon sometimes appear colorful? The effect, called a lunar corona, is created by the quantum mechanical diffraction of light around individual, similarly-sized water droplets in an intervening but mostly-transparent cloud. Since light of different colors has different wavelengths, each color diffracts differently.

APOD: 2024 October 14 Б Comet Tsuchinshan ATLAS Over the Lincoln Memorial
14.10.2024

Go outside at sunset tonight and see a comet! C/2023 A3 (TsuchinshanБATLAS) has become visible in the early evening sky in northern locations to the unaided eye. To see the comet, look west through a sky with a low horizon.