Space at
your fingertips.
"I want to know why the universe exist, why there is something greater than nothing."
Steven Hawking
Scientist, Space Lover
What would it be like to fly free in space? At about 100 meters from the cargo bay of the space shuttle Challenger, Bruce McCandless II was living the dream -- floating farther out than anyone had ever been before. Guided by a Manned Maneuvering Unit (MMU), astronaut McCandless, pictured, was floating free in space. During Space Shuttle mission 41-B in 1984, McCandless and fellow NASA astronaut Robert Stewart were the first to experience such an "untethered space walk". The MMU worked by shooting jets of nitrogen and was used to help deploy and retrieve satellites. With a mass over 140 kilograms, an MMU is heavy on Earth, but, like everything, is weightless when drifting in orbit. The MMU was later replaced with the SAFER backpack propulsion unit.
Fittingly, 1999 saw a decade of astronomical discoveries to an end with portents of things to come - embodied in new spacecraft, telescopes, and perspectives to explore the distant Universe across the electromagnetic spectrum. X-ray astronomy in particular will likely flourish in coming years, judging from this year's successful launch of the triple-barrelled X-ray Multi-Mirror satellite and spectacular first results from the orbiting Chandra X-ray Observatory. Ground-based astronomy will flourished too as very large telescopes and new instruments have come online or near completion. Radio astronomers also achieved an observational milestone this year with the record breaking VLBI observations from a network of radio telescopes as large as planet Earth. But the APOD editors' favorite astronomical screensaver of 1999 has leveraged the phenomenonal growth of the internet and the personal computer boom to support the Search for ExtraTerrestrial Intelligence in the SETI@home project - which has now likely involved more computer power than any other project in history. News: APOD Home Switched During Y2K Transition
What's happening at the center of active galaxy 3C 75? The two bright sources at the center of this composite x-ray (blue)/ radio (pink) image are co-orbiting supermassive black holes powering the giant radio source 3C 75. Surrounded by multimillion degree x-ray emitting gas, and blasting out jets of relativistic particles the supermassive black holes are separated by 25,000 light-years. At the cores of two merging galaxies in the Abell 400 galaxy cluster they are some 300 million light-years away. Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets' consistent swept back appearance is most likely due to their common motion as they speed through the hot cluster gas at about 1200 kilometers per second. Such spectacular cosmic mergers are thought to be common in crowded galaxy cluster environments in the distant universe. In their final stages, the mergers are expected to be intense sources of gravitational waves.
Expanse