APOD: 2024 December 23 Б Christmas Tree Aurora
22.12.2024

It was December and the sky lit up like a Christmas tree. Shimmering, the vivid green, blue, and purple auroral colors that formed the tree-like apparition were caused by high atmospheric oxygen and nitrogen reacting to a burst of incoming electrons.

APOD: 2025 January 21 Б Comet ATLAS over Brasilia
20.01.2025

What's that in the sky? Above the city, above most clouds, far in the distance: it's a comet. Pictured, the impressive tail of Comet C/2024 G3 (ATLAS) was imaged from Brasцlia, Brazil four days ago.

Earth's Plasmasphere
30.01.2001

Our Earth is surrounded by plasma. The overall shape that this ionized gas plasmasphere takes was discovered last year by NASA's robot IMAGE spacecraft, and shown in the recently released above image in ultraviolet light.

A Martian Autumn Begins
23.09.1997

Today is the first day of Autumn in the Northern Hemisphere of Planet Earth. The Autumnal Equinox occured yesterday at 7:56 pm EDT as the Sun crossed the celestial equator from North to South.

APOD: 2023 June 26 Б The Belt of Venus over Mount Everest
25.06.2023

You've surely seen it, but you might not have noticed it. During a cloudless twilight, just before sunrise or after sunset, part of the atmosphere above the horizon appears slightly dark and off-color.

Comet NEAT in Southern Skies
5.03.2003

After last month's dramatic swoop past the Sun, Comet NEAT (C/2002 V1) appeared as a naked-eye comet, emerging from the evening twilight in planet Earth's southern skies. On March 1st, New Zealand...

Iridescent Clouds from the Top of the World Highway
7.02.2011

Why would a cloud appear to be different colors? A relatively rare phenomenon known as iridescent clouds can show unusual colors vividly or a whole spectrum of colors simultaneously. These clouds are formed of small water droplets of nearly uniform size.

Sunrise Solstice over Stonehenge
19.06.2021

Today the Sun reaches its northernmost point in planet Earth's sky. Called a solstice, many cultures mark this date as a change of seasons -- from spring to summer in Earth's Northern Hemisphere and from fall to winter in Earth's Southern Hemisphere.

APOD: 2024 July 7 Б Iridescent Clouds over Sweden
6.07.2024

Why are these clouds multi-colored? A relatively rare phenomenon in clouds known as iridescence can bring up unusual colors vividly -- or even a whole spectrum of colors simultaneously. These polar stratospheric clouds also, known as nacreous and mother-of-pearl clouds, are formed of small water droplets of nearly uniform size.

APOD: 2025 July 7 Б Interstellar Comet 3I ATLAS
6.07.2025

It came from outer space. An object from outside our Solar System is now passing through at high speed. Classified as a comet because of its gaseous coma, 3I/ATLAS is only the third identified macroscopic object as being so alien.