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Astronomy Picture Of the Day (APOD)
Occultations and Rising Moons
13.05.1998
On April 23, the rising crescent Moon occulted (passed in front of) Venus and Jupiter. The double occultation was a rare event and only visible from certain locations tracing a path across Earth's surface. This dramatic telephoto picture was taken at one such location, Ascension Island in the South Atlantic.
Callisto Enhanced
12.05.1998
Callisto is half rock and half ice. This moon of Jupiter is approximately the size of the planet Mercury, making it the third largest moon in the Solar System, after Ganymede and Titan. Callisto...
Callisto in True Color
11.05.1998
Callisto's surface has many stories to tell. The most distant of Jupiter's Galilean Moons, Callisto shows the highest density of impact craters in the Solar System, but harbors no volcanoes or even any large mountains. Callisto's surface is laced with cracks and craters from
Skylab Over Earth
10.05.1998
Skylab was an orbiting laboratory launched by a Saturn V rocket in May 1973. Skylab was visited three times by NASA astronauts who sometimes stayed as long as two and a half months. Many scientific tests were performed on Skylab, including astronomical observations in ultraviolet and X-ray light.
The Water Vapor Channel
9.05.1998
What alien planet's bizarre landscape lurks below these fiery-looking clouds? It's only Planet Earth, of course ... as seen on the Water Vapor Channel. Hourly, images like this one (an infrared image shown in false color) are brought to you by the orbiting Geostationary Operational Environmental Satellites' (GOES) multi-channel imagers.
A Gamma Ray Burst Supernova
8.05.1998
Did a gamma-ray burst precede this supernova? This intriguing suggestion came to light yesterday with the discovery of an evolving supernova that is potentially coincident with the position of gamma-ray burst GRB 980425, which occurred just two weeks ago. If true, this would tie together the two most violent phenomena known in the universe.
A Powerful Gamma Ray Burst
7.05.1998
Gamma-ray bursts are thought to be the most powerful explosions in the Universe, yet the cause of these high-energy flashes remains a mystery. Blindingly bright for space-based gamma-ray detectors the burst sources are so faint at visible wavelengths that large telescopes and sensitive cameras are required to search for them.
Beijing Ancient Observatory
6.05.1998
Did observatories exist before telescopes? One example that still stands today is the Beijing Ancient Observatory in China. Starting in the 1400s astronomers erected large instruments here to enable them to measure star and planet positions with increasing accuracy.
Aurora at Midnight
5.05.1998
What's happening behind those trees? Aurora. This picture was taken at midnight near Fairbanks, Alaska, and captures familiar trees, common clouds, and a glowing sky markedly different than a sunset. Particularly strange is the green auroral ring caused by ionized oxygen high in the Earth's atmosphere.
M57: The Ring Nebula
4.05.1998
It looked like a ring on the sky. Hundreds of years ago astronomers noticed a nebula with a most unusual shape. Now known as M57 or NGC 6720, the gas cloud became popularly known as the Ring Nebula.
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