A Sonic Boom
19.08.2007

Is this what a sonic boom looks like? When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane.

The Anthe Arc around Saturn
10.09.2008

What created this unusual partial ring around Saturn? Discovered last year, the arc was captured in clear detail only two months ago by the Saturn-orbiting Cassini spacecraft. Since the arc occupies the same orbit...

APOD: 2026 August 9 Б Contemplating the Sun
9.08.2026

Have you contemplated your home star recently? Featured here, a Sun partially eclipsed on the top left by the Moon is also seen eclipsed by earthlings contemplating the eclipse below. This spectacular menagerie...

October Skylights
8.11.2000

With brilliant Venus above the western horizon at sunset and Jupiter and Saturn high in the east by early evening, November's night sky is filled with bright planets. October's sky featured bright planets as well and, triggered by the active Sun, some lovely auroral displays.

A Patch of Spherules on Mars
16.02.2004

Some patches of Mars are full of mysterious tiny spherules. The microscopic imager on board the Opportunity rover on Mars recorded, last week, the above image showing over a dozen. The image was taken near a rock outcrop called Stone Mountain and spans roughly 6 centimeters across.

The View from Chajnantor
23.11.2011

From an altitude of over 5,000 meters, the night sky view from Chajnantor Plateau in the Chilean Andes is breathtaking in more ways than one. The dark site's rarefied atmosphere, at about 50 percent sea level pressure, is also extremely dry.

Alnitak, Alnilam, Mintaka
12.12.2013

Alnitak, Alnilam, and Mintaka, are the bright bluish stars from east to west (lower right to upper left) along the diagonal in this gorgeous cosmic vista. Otherwise known as the Belt of Orion, these three blue supergiant stars are hotter and much more massive than the Sun.

The North Celestial Tower
16.07.2016

If you climbed to the top of this 13th century stone tower, it looks like you could reach out and touch the North Celestial Pole, the point at the center of all the star trail arcs.

A Sonic Boom
4.05.2003

Many people have heard a sonic boom, but few have seen one. When an airplane travels at a speed faster than sound, density waves of sound emitted by the plane cannot precede the plane, and so accumulate in a cone behind the plane.

Searching for Meteorites in Antarctica
7.09.2008

Where is the best place on Earth to find meteorites? Although meteors fall all over the world, they usually just sink to the bottom of an ocean, are buried by shifting terrain, or are easily confused with terrestrial rocks.