September Aurora
21.09.2012

September's equinox arrives tomorrow as the Sun crosses the celestial equator heading south. The event marks the astronomical beginning of spring in the southern hemisphere and autumn in the north. And though the connection is still puzzling, the equinox seasons bring an increase in geomagnetic storms.

APOD: 2025 June 29 Б Dark Sand Cascades on Mars
28.06.2025

Are these trees growing on Mars? No. Groups of dark brown streaks have been photographed by the Mars Reconnaissance Orbiter on melting pinkish sand dunes covered with light frost. The featured image was taken in 2008 April near the North Pole of Mars.

Moonset Over Pleasant Bay
29.03.2010

It was a sky for the imagination. In the early evening last week, the sky illuminating the unaided eye was perhaps even more illuminating to the mind's eye. The unaided eye saw clouds...

Tunguska: The Largest Recent Impact Event
13.11.2007

Yes, but can your meteor do this? The most powerful natural explosion in recent Earth history occurred on 1908 June 30 when a meteor exploded above the Tunguska River in Siberia, Russia. Detonating with...

Tunguska: The Largest Recent Impact Event
2.10.2011

Yes, but can your meteor do this? The most powerful natural explosion in recent Earth history occurred on 1908 June 30 when a meteor exploded above the Tunguska River in Siberia, Russia. Detonating with...

I Brought You the Moon
31.03.2018

I love you so much that I brought you the Moon. Please take it before this tree becomes more interested. Also the Moon is heavier than I thought. And I foolishly picked it up by the hot side by mistake. But it is for you and, well, the others reading this APOD.

Nebulae For Christmas
24.12.1998

If our Galaxy were a Christmas tree, planetary nebulae would adorn it like colorful lighted ornaments twinkling on a cosmic scale. Glowing shrouds of gas ejected by red giant stars, planetary nebulae like...

Northern Green Flash
23.06.2012

As seen from Frösön island in northern Sweden the Sun did set a day after the summer solstice. From that location below the arctic circle it settled slowly behind the northern horizon.

Aurora Over Alaska
3.03.1998

Higher than the highest mountain, higher than the highest airplane, lies the realm of the aurora. Aurora rarely reach below 60 kilometers, and can range up to 1000 kilometers. Aurora light results from solar electrons and protons striking molecules in the Earth's atmosphere.

Galaxy Dwingeloo 1 Emerges
28.02.1997

Sometimes you can't see the forest for the trees. But if you look closely at the center of the above photograph, you will see a whole spiral galaxy behind the field of stars.