Lightning on Earth
17.07.2000

Nobody knows what causes lightning. It is known that charges slowly separate in some clouds causing rapid electrical discharges (lightning), but how electrical charges get separated in clouds remains a topic of much research.

In the Center of NGC 6559
29.06.2004

Bright gas and dark dust permeate the space between stars in the center of a nebula known as NGC 6559. The gas, primarily hydrogen, is responsible for the diffuse red glow of the emission nebula.

The Solar Spectrum
29.06.2003

It is still not known why the Sun's light is missing some colors. Shown above are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device.

A Galaxy Collision in NGC 6745
2.11.2000

Galaxies don't normally look like this. NGC 6745 actually shows the results of two galaxies that have been colliding for only hundreds of millions of years. Just off the above photograph to the lower right is the smaller galaxy, moving away.

Pelican Nebula Ionization Front
3.07.2000

The Pelican Nebula is slowly being transformed. IC 5070, the official designation, is divided from the larger North America Nebula by a molecular cloud filled with dark dust. The Pelican, however, receives much study because it is a particularly active mix of star formation and evolving gas clouds.

Elements of Nearby Spiral M33
27.09.2001

Spiral galaxy M33 is a mid-sized member of our Local Group of Galaxies. M33 is also called the Triangulum Galaxy for the constellation in which it resides. About four times smaller (in radius) than...

The Solar Spectrum
27.02.2005

It is still not known why the Sun's light is missing some colors. Shown above are all the visible colors of the Sun, produced by passing the Sun's light through a prism-like device.

Stellar Spectral Types: OBAFGKM
18.04.2004

Astronomers divide stars into different spectral types. First started in the 1800s, the spectral type was originally meant to classify the strength of hydrogen absorption lines. A few types that best describe the temperature of the star remain in use today.

The Horsehead Nebula
13.07.2003

One of the most identifiable nebulae in the sky, the Horsehead Nebula in Orion, is part of a large, dark, molecular cloud. Also known as Barnard 33, the unusual shape was first discovered on a photographic plate in the late 1800s.

The Incredible Expanding Crab
27.12.2001

The Crab Nebula is cataloged as M1, the first on Charles Messier's famous list of things which are not comets. In fact, the Crab is now known to be a supernova remnant, an expanding cloud of debris from the explosion of a massive star.