A Sky Full Of Hydrogen
13.01.2001

Interstellar space is filled with extremely tenuous clouds of gas which are mostly Hydrogen. The neutral hydrogen atom (HI in astronomer's shorthand) consists of 1 proton and 1 electron. The proton and electron spin like tops but can have only two orientations; spin axes parallel or anti-parallel.

The Southern Cliff in the Lagoon
11.05.2011

Undulating bright ridges and dusty clouds cross this close-up of the nearby star forming region M8, also known as the Lagoon Nebula. A sharp, false-color composite of narrow band visible and broad band near-infrared...

Io: Moon over Jupiter
7.08.2016

How big is Jupiter's moon Io? The most volcanic body in the Solar System, Io (usually pronounced "EYE-oh") is 3,600 kilometers in diameter, about the size of planet Earth's single large natural satellite.

Jupiter: At The Belt-Zone Boundary
10.03.1997

Jupiter's thick atmosphere is striped by wind-driven cloud bands that remain fixed in latitude - dark colored bands are known as belts while light colored bands are zones. At Jupiter's belt-zone boundaries the shearing wind velocities can reach nearly 300 miles per hour.

A Fire Rainbow Over New Jersey
10.06.2008

What is that inverted rainbow in the sky? Sometimes known as a fire rainbow for its flame-like appearance, a circumhorizon arc is created by ice, not fire. For a circumhorizon arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds are present.

A Partial Lunar Eclipse
28.06.2010

What's happened to the Moon? This past weekend, once again, part of the Moon moved through the Earth's shadow. This happens about once or twice a year, on the average, but not each month since the Moon's orbit around the Earth is slightly tilted.

An Orion Deep Field
15.01.2004

Adrift 1,500 light-years away in one of the night sky's most recognizable constellations, the glowing Orion Nebula and the dark Horsehead Nebula are contrasting cosmic vistas. They both appear in this stunning composite digital image assembled from over 20 hours of data that includes exposures filtered to record emission from hydrogen atoms.

M81 in Ursa Major
27.04.2007

One of the brightest galaxies in planet Earth's sky and similar in size to the Milky Way, big, beautiful spiral M81 lies 11.8 million light-years away in the northern constellation Ursa Major. This...

A Halo Around the Moon
21.04.2003

Have you ever seen a halo around the Moon? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens.

The Rosette Nebula
14.02.2012

The Rosette Nebula is not the only cosmic cloud of gas and dust to evoke the imagery of flowers -- but it is the most famous. At the edge of a large molecular cloud...