Hubble s Cosmic Reef
24.04.2020

These bright ridges of interstellar gas and dust are bathed in energetic starlight. With its sea of young stars, the massive star-forming region NGC 2014 has been dubbed the Cosmic Reef. Drifting just...

Retrograde Mars
13.06.2010

Why would Mars appear to move backwards? Most of the time, the apparent motion of Mars in Earth's sky is in one direction, slow but steady in front of the far distant stars. About every two years, however, the Earth passes Mars as they orbit around the Sun.

A RADARSAT Map of Antarctica
15.11.1999

It's not easy to make a map of Antarctica. Earth's southern most continent is so cold and inhospitable that much of it remains unexplored. From space, though, it is possible to map this entire region by radar: by systematically noting how long it takes for radio waves to reflect off the terrain.

Iridium 52: Not A Meteor
22.10.1999

While hunting for meteors in the night sky above the White Mountains near Bishop, California, astrophotographer James Young instead captured this brilliant celestial apparition. Recorded near twilight on August 13, the bright streak is not the flash of a meteor trail but sunlight glinting from a satellite.

The First Explorer
12.08.2006

Inaugurating the era of space exploration for the US, the First Explorer, a thirty pound satellite, was launched into Earth orbit on February 1, 1958 by the Army Ballistic Missle Agency. Explorer I carried instruments to measure temperatures, micrometeorite impacts, and an experiment designed by James A.

Aurora and Orion
25.01.1997

Looking toward the south from low Earth orbit, the crew of the Space Shuttle Endeavor made this stunning time exposure of the Aurora Australis or southern lights in April of 1994. Aurora are visible at high northern latitudes as well, with the northern lights known as Aurora Borealis.

APOD: 2025 February 17 Б SpaceX Rocket Launch Plume over California
16.02.2025

What's happened to the sky? Last Monday, the photogenic launch plume from a SpaceX rocket launch created quite a spectacle over parts of southern California and Arizona. Looking at times like a giant...

A Near Record Ozone Hole in 2003
6.10.2003

As expected, the ozone hole near Earth's South Pole is back again this year. This year's hole, being slightly larger than North America, is larger than last year but short of the record set on 2000 September 10. Ozone is important because it shields us from damaging ultraviolet sunlight.

Collinder 399: The Coat Hanger
11.01.2007

Is this coat hanger a star cluster or an asterism? This cosmic hang-up has been debated over much of last century, as astronomers wondered whether this binocular-visible object is really a physically associated open cluster or a chance projection. Chance star projections are known as asterisms, an example of which is the popular Big Dipper.

3D Mercury Transit
24.11.2006

Mercury is now visible shortly before dawn, the brightest "star" just above the eastern horizon. But almost two weeks ago Mercury actually crossed the face of the Sun for the second time in the 21st century.