100 Hours of Astronomy Begins
2.04.2009

Today, 100 Hours of Astronomy begins, a cornerstone project of the International Year of Astronomy 2009 celebrating the 400th anniversary of Gallileo's original telescopic exploration of the sky. Running from April 2 through...

APOD: 2009 April 7 The Colliding Spiral Galaxies of Arp 274
7.04.2009

Two galaxies are squaring off in Virgo and here are the latest pictures. When two galaxies collide, the stars that compose them usually do not. This is because galaxies are mostly empty space and, however bright, stars only take up only a small fraction of that space.

Martian Moon Phobos from Mars Express
30.11.2010

Why is Phobos so dark? Phobos, the largest and innermost of two Martian moons, is the darkest moon in the entire Solar System. Its unusual orbit and color indicate that it may be a captured asteroid composed of a mixture of ice and dark rock.

A Green Flash from the Sun
3.01.2011

Many think it is just a myth. Others think it is true but its cause isn't known. Adventurers pride themselves on having seen it. It's a green flash from the Sun. The truth is the green flash does exist and its cause is well understood.

Shell Galaxies in Pisces
25.02.2011

This colorful cosmic skyscape features a peculiar system of galaxies cataloged as Arp 227 some 100 million light-years distant. Swimming within the boundaries of the constellation Pisces, Arp 227 consists of the two galaxies prominent on the left; the curious shell galaxy NGC 474 and its blue, spiral-armed neighbor NGC 470.

Asperatus Clouds Over New Zealand
16.04.2016

What kind of clouds are these? Although their cause is presently unknown, such unusual atmospheric structures, as menacing as they might seem, do not appear to be harbingers of meteorological doom. Known informally...

The Aurora and the Sunrise
30.04.2018

On the International Space Station (ISS), you can only admire an aurora until the sun rises. Then the background Earth becomes too bright. Unfortunately, after sunset, the rapid orbit of the ISS around the Earth means that sunrise is usually less than 47 minutes away.

Comet 46P Wirtanen
14.11.2018

Periodic Comet 46P/Wirtanen is now the brightest comet in the night sky, but too faint to be seen by eye. From dark sky sites it could just become naked-eye visible though, as it's 5.4 year long looping orbit takes it closest to Earth and the Sun in mid December.

Milky Way over Pyramid of the Feathered Serpent
16.06.2019

To see the feathered serpent descend the Mayan pyramid requires exquisite timing. You must visit El Castillo -- in Mexico's YucatАn Peninsula -- near an equinox. Then, during the late afternoon if the sky is clear, the pyramid's own shadows create triangles that merge into the famous illusion of the slithering viper.

Shell Galaxies in Pisces
26.08.2020

This intergalactic skyscape features a peculiar system of galaxies cataloged as Arp 227 some 100 million light-years distant. Swimming within the boundaries of the constellation Pisces, Arp 227 consists of the two galaxies prominent right of center, the curious shell galaxy NGC 474 and its blue, spiral-armed neighbor NGC 470.