Exploring Space: Images from NASA

To fix Hubble’s blurry vision, NASA sent the shuttle Endeavour on a repair trip in December of 1993. The mission - STS-61 -  was the fifty-ninth time a shuttle was launched into space.

During the eleven-day trip, astronauts set a record of five space walks, spanning more than thirty-five hours.  They worked on  the telescope as it was “docked” in the shuttle’s payload bay.

Astronauts have made several more trips to Hubble,  upgrading, servicing and then releasing one of the world’s most treasured sources of space information. A famous picture of the telescope, as it appears during its working state,  was taken in February, 1997, as the shuttle Discovery neared the orbiting observatory.

Atlantis, in mission STS-125, is scheduled to make a "final" repair trip to the orbiting space telescope.  A risky mission, due to space debris in Hubble's orbit, NASA officials ordered Endeavour to stand-by - on the launch pad - in case Atlantis, or the crew, encountered difficulties.

After Hubble’s vision was corrected, it began to send clear electronic images to its base in Maryland. One of the most stunning is of the Eagle Nebula -  also called  M16 -  in the Serpens constellation.

What, exactly, is a nebula? And...what are some of the most notable?