|MadSci Network: Astronomy|
NASA has actually sent messages into space on 4 spacecraft: Pioneer 10 (launched 1972), Pioneer 11 (launched 1973), Voyager 1 and Voyager 2 (both launched 1977). The Pioneer craft carried a simple plaque, describing the origin of the spacecraft. The Voyagers carried a metal record with more information, sounds and images.
What happened to them? They're just going and going, out into deep space, forever! No signals have been received from Pioneer 11 since 1995 - it's headed for a constellation named Aquila and will arrive there in about 4 million years. Pioneer 10 is now about 14 billion km from Earth and was last heard from in 2003.
The Voyagers are still in contact with Earth. Voyager 1 is now the most distant man-made object, over 15 billion km away. The craft are still sending back interesting information about the boundary between our solar system and deep space. At this distance, the sun is just a point of light - like any bright star in the sky.
Here are some links for you:
Pioneer 10 & 11 website
Pioneer Mission Status
Voyager project website
The Voyager golden record
There are also Wikipedia pages for all 4 spacecraft:
Try the links in the MadSci Library for more information on Astronomy.