Astronomy Picture Of the Day (APOD)
Help NASA Classify Martian Craters7.01.2001
The large Martian crater above just left of center: is this a fresh crater, a degraded crater, or a ghost crater? Complex image recognition tasks like these are currently done more reliably by a human than a computer.
Tycho Brahe Measures the Sky
6.01.2001
Tycho Brahe was the most meticulous astronomical observer of his time. Brahe, who lived between 1546 and 1601, set out to solve the day's most pressing astronomical problem: to determine whether the Earth or the Sun was at the center of the Solar System.
Apollo 17's Moonship
5.01.2001
Awkward and angular looking, Apollo 17's lunar module Challenger was designed for flight in the vacuum of space. This sharp picture from the command module America, shows Challenger's ascent stage in lunar orbit.
Second Millennium, Last Eclipse
4.01.2001
Christmas Day 2000 featured the final eclipse of the Second Millennium -- a partial solar eclipse visible from much of North America. Astrophotographer Phil Rau recorded the entire event on a single image as the Sun and Moon arced through winter skies above Cary, North Carolina, USA.
Third Millennium, First Eclipse
3.01.2001
The first eclipse of the third millennium is coming up! A total lunar eclipse mainly visible from Europe, Asia, and Africa, will occur on January 9th as the full Moon glides through the long, but not so dark shadow of planet Earth. Why not so dark?
M8: In the Center of the Lagoon Nebula
2.01.2001
In the center of the Lagoon Nebula one finds glowing gas, star clusters, and dense knots of gas and dust just now forming stars. The young open cluster of stars, designated NGC 6523, can be seen in the center of the above image. These stars emit energetic light that ionizes the surrounding hydrogen gas.
Jupiter, Europa, and Callisto
1.01.2001
As the robot Cassini spacecraft rounds Jupiter on its way toward Saturn, it has taken a sequence of images of the gas giant with its four largest moons. Previously released images have highlighted Ganymede and Io. Pictured above are the two remaining Galilean satellites: Europa and Callisto.
The Millennium that Defines Universe
31.12.2000
Welcome to millennium three. During millennium two, humanity continually redefined its concept of "Universe": first as spheres centered on the Earth, in mid-millennium as the Solar System, a few centuries ago as the Galaxy, and within the last century as the matter emanating from the Big Bang.
The Millennium that Defined Earth
30.12.2000
When the second millennium began, people generally knew that the Earth was round, but few saw much of it beyond their local village. As the millennium progressed, humans mapped the continents, circumnavigated the globe, and determined the composition of the Earth.
A Year of Resolving Backgrounds
29.12.2000
No matter which direction you look, no matter what type of light you see, the sky glows - but why? The sources of many of these background radiations have remained long-standing puzzles, but this millennial year brought some partial resolutions.
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