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Astronomy Picture Of the Day (APOD)
A Wolf-Rayet Star Blows Bubbles
3.01.1997
Wolf-Rayet stars can blow bubbles. These unusual stars are much hotter and more luminous than our Sun. All extremely massive stars will eventually evolve though a Wolf-Rayet phase. Approximately 200 Wolf-Rayet stars are known in our Milky Way Galaxy. Wolf-Rayet stars generate bubbles because they continually eject their outer atmosphere as a stellar wind.
Bubbles and Arcs in NGC 2359
2.01.1997
What caused the bubbles and arcs in NGC 2359? The main suspect is the Wolf-Rayet star in the center of one of the bubbles - visible slightly below and to the right of the center of the above photograph.
Aurora Over Circle, Alaska
1.01.1997
Aurora can make spectacular sights. This particular aurora was photographed hovering over the town of Circle, Alaska. Although Aurora might first appear to be moonlit clouds, they only add light to the sky, and hence can not block background stars from view.
Io Rotating
31.12.1996
Are any volcanoes on Io currently erupting? To help answer this, scientists instructed the robot spacecraft Galileo to take hourly pictures of this moon of Jupiter prior to its most recent encounter. The most obvious changes in Io are due to the changing amount of sunlight reflected from the moon to the spacecraft.
X-Ray Earth
30.12.1996
The Earth glows in many kinds of light, including the energetic X-ray band. Actually, the Earth itself does not glow - only aurora produced high in the Earth's atmosphere. Above is the first picture of the Earth in X-rays, taken in March with the orbiting Polar satellite. Bright X-ray emission is shown in red.
Dark Bok Globules in IC 2944
29.12.1996
The dark spots in the above picture are not photographic defects but an unusual type of interstellar cloud known as a Bok globule. Bok globules, named after astronomer Bart Bok who studied them extensively, are small dark clouds made of gas and dust that are typically condensing to form a
CG4: A Ruptured Cometary Globule
28.12.1996
The odd looking "creature" to the right of center in the above photo is a gas cloud known as a cometary globule. This globule, however, has ruptured. Cometary globules are typically characterized by dusty heads and elongated tails.
HET: The New Largest Optical Telescope
27.12.1996
Most of our universe is too dim to see. To peer into our cosmos' unknown depths, astronomers must deploy new tools - and the classic new tool is a larger telescope. Pictured above is the new Hobby-Eberly Telescope (HET) which recently declared "first light" in western Texas.
Carl Sagan 1934-1996
26.12.1996
Carl Sagan died last Friday at the age of 62. Sagan was the world's most famous astronomer. Among his many activities as a scientist, he contributed to the discovery that the atmosphere...
An Earth Ornament
25.12.1996
The Apollo 8 astronauts spent the 1968 Christmas Season in lunar orbit, returning with striking images of the Moon and Earth from space which inspired the world. While in lunar orbit...
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