Moon Pi and Mountain Shadow
13.03.2025

What phase of the Moon is 3.14 radians from the Sun? The Full Moon, of course. Even though the Moon might look full for several days, the Moon is truly at its full phase when it is Pi radians (aka 180 degrees) from the Sun in ecliptic longitude.

Rotating Moon from LRO
18.07.2020

No one, presently, sees the Moon rotate like this. That's because the Earth's moon is tidally locked to the Earth, showing us only one side. Given modern digital technology, however, combined with many detailed images returned by the Lunar Reconnaissance Orbiter (LRO), a high resolution virtual Moon rotation movie has been composed.

Phobos: Doomed Moon of Mars
6.04.2003

This moon is doomed. Mars, the red planet named for the Roman god of war, has two tiny moons, Phobos and Deimos, whose names are derived from the Greek for Fear and Panic. These...

Moon Corona, Halo, and Arcs over Manitoba
23.02.2020

Yes, but could you get to work on time if the Moon looked like this? As the photographer was preparing to drive to work, refraction, reflection, and even diffraction of moonlight from millions of falling ice crystals turned the familiar icon of our Moon into a menagerie of other-worldly halos and arcs.

Eclipsed Moon in Infrared
7.11.2003

The total lunar eclipse of September 1996 disappointed many observers in North America who were cursed with cloudy skies. However, the Midcourse Space Experiment (MSX) satellite had a spectacular view from Earth orbit and SPIRIT III, an on board infrared telescope, was used to repeatedly image the moon during the eclipse.

Full Moon in Earth's Shadow
7.04.2015

Last week the Full Moon was completely immersed in Earth's dark umbral shadow, just briefly though. The total phase of the April 4, 2015 lunar eclipse lasted less than 5 minutes, the shortest total lunar eclipse of the century.

Colors of the Moon
10.11.2020

What color is the Moon? It depends on the night. Outside of the Earth's atmosphere, the dark Moon, which shines by reflected sunlight, appears a magnificently brown-tinged gray. Viewed from inside the Earth's atmosphere, though, the moon can appear quite different.

Hammer Versus Feather on the Moon
1.11.2011

If you drop a hammer and a feather together, which reaches the ground first? On the Earth, it's the hammer, but is the reason only because of air resistance? Scientists even before Galileo have pondered and tested this simple experiment and felt that without air resistance, all objects would fall the same way.

Full Moon, Full Mars
17.01.2025

On January 13 a Full Moon and a Full Mars were close, both bright and opposite the Sun in planet Earth's sky. In fact Mars was occulted, passing behind the Moon, when viewed from some locations in North America and northwest Africa.

APOD: 2025 March 25 Б A Blue Banded Blood Moon
24.03.2025

What causes a blue band to cross the Moon during a lunar eclipse? The blue band is real but usually quite hard to see. The featured HDR image of last week's lunar eclipse, however -- taken from Norman, Oklahoma (USA) -- has been digitally processed to exaggerate the colors.