Hot Stars in the Southern Milky Way
7.05.1999

Hot blue stars, red glowing hydrogen gas, and dark, obscuring dust clouds are strewn through this dramatic region of the Milky Way in the southern constellation of Ara (the Altar). About 4,000 light-years from Earth, the stars at the left are young, massive, and energetic.

Hot Stars in the Southern Milky Way
22.12.2001

Hot blue stars, red glowing hydrogen gas, and dark, obscuring dust clouds are strewn through this dramatic region of the Milky Way in the southern constellation of Ara (the Altar). About 4,000 light-years from Earth, the stars at the left are young, massive, and energetic.

The First Lunar Observatory
8.06.1996

The first and only lunar astronomical observatory was deployed by the Apollo 16 crew in 1972. The Far Ultraviolet Camera / Spectrograph used a 3-inch diameter telescope to photograph the Earth, various nebulae, star clusters, and the Large Magellanic Cloud.

Equinox and Eruptive Prominence
23.09.1999

Today, the Sun crosses the celestial equator and seasons change from Summer to Fall in the north and Winter to Spring in the southern hemisphere. Defined by the Sun's position in sky the event is known as an equinox - the length of daylight is equal to the length of night.

Ozone Hole Reduced
13.10.1999

Although a new ozone hole has formed again this year over the South Pole, this time it is a little bit smaller than the year before. Ozone is important because it shields us from damaging ultraviolet sunlight. Ozone is vulnerable, though, to CFCs and halons being released into the atmosphere.

A Solar Prominence Unfurls
4.10.2008

On September 29, this magnificent eruptive solar prominence lifted away from the Sun's surface, unfurling into space over the course of several hours. Suspended in twisted magnetic fields, the hot plasma structure is many times the size of planet Earth and was captured in this view by the Sun-watching STEREO (Ahead) spacecraft.

IC 4628: The Prawn Nebula
4.07.2016

South of Antares, in the tail of the nebula-rich constellation Scorpius, lies emission nebula IC 4628. Nearby hot, massive stars, millions of years young, radiate the nebula with invisible ultraviolet light, stripping electrons from atoms. The electrons eventually recombine with the atoms to produce the visible nebular glow, dominated by the red emission of hydrogen.

A Solar Prominence Erupts
24.09.2001

Our Sun is still very active. Last year, our Sun went though Solar Maximum, the time in its 11-year cycle where the most sunspots and explosive activities occur. Sunspots, the Solar Cycle, and solar prominences are all caused by the Sun's changing magnetic field.

A Small Double Ozone Hole in 2002
22.10.2002

As expected, the ozone hole near Earth's South Pole is back again this year. This time, however, it's smaller than the past two years, and has an unusual double lobe structure. Ozone is important because it shields us from damaging ultraviolet sunlight.

Hydrogen Trifid
28.08.1998

Clouds of glowing hydrogen gas mingle with dark dust lanes in the Trifid Nebula, a star forming region in the constellation Sagittarius. In this and other similar emission nebulae, energetic ultraviolet light from an embedded hot young star strips electrons from the surrounding hydrogen atoms.