Southwest Mercury
16.02.2003

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.

APOD is Two Years Old Today
16.06.1997

The first Astronomy Picture of the Day (APOD) appeared two years ago today. Pictured above is a scene surrounding the creation of an early APOD, depicting the famous astronomer Tycho Brahe demonstrating a celestial globe to Emperor Rudolph II. The image of a possible optical counterpart to a gamma-ray burst appears on the back wall.

The Moving Moons of Saturn
27.06.2006

The moons of Saturn never stop. A space traveler orbiting the ringed giant planet would witness a continuing silent dance where Saturn's multiple moons pass near each other in numerous combinations. Like a miniature Solar System, the innermost moons orbit Saturn the fastest.

From the Moon to the Earth
19.07.2009

After the most famous voyage of modern times, it was time to go home. After proving that humanity has the ability to go beyond the confines of planet Earth, the first humans to walk...

A Mercury Transit Sequence
4.05.2016

This coming Monday, Mercury will cross the face of the Sun, as seen from Earth. Called a transit, the last time this happened was in 2006. Because the plane of Mercury's orbit is not exactly coincident with the plane of Earth's orbit, Mercury usually appears to pass over or under the Sun.

Space Station in the Moon
6.02.2009

On February 2nd, a first quarter Moon shone in planet Earth's early evening sky. As seen from a location on the US west coast near Mt. Hamilton, California, the International Space Station also arched above the horizon, crossing in front of the Moon's sunlit surface. The space station's transit lasted 0.49 seconds.

An Evening Sky Conjunction
19.02.2015

Eight years ago, an evening sky held this lovely pairing of a young crescent Moon and brilliant Venus. Seen near the western horizon, the close conjunction and its wintry reflection were captured from Bolu, Turkey, planet Earth on February 19, 2007.

Meteor and Milky Way over the Mediterranean
23.08.2022

Careful planning made this a nightscape to remember. First, the night itself was chosen to occur during the beginning of this year's Perseid Meteor Shower. Next, the time of night was chosen to be before the bright Moon would rise and dominate the night sky's brightness.

Solstice Illuminated: A Year of Sky
22.12.2019

Can you find which day is the winter solstice? Each panel shows one day. With 360 movie panels, the sky over (almost) an entire year is shown in time lapse format as recorded by a video camera on the roof of the Exploratorium museum in San Francisco, California.

Mercury as Revealed by MESSENGER
23.07.2017

Mercury had never been seen like this before. In 2008, the robotic MESSENGER spacecraft buzzed past Mercury for the second time and imaged terrain mapped previously only by comparatively crude radar. The featured image was recorded as MESSENGER looked back 90 minutes after passing, from an altitude of about 27,000 kilometers.