Pale Blue Dot
Pale Blue Dot (English " pale blue dot " ) is the name of a photograph of Earth, taken by the Voyager 1 spacecraft from a distance of about 6.4 billion kilometers, the largest distance from which ever a photo of the earth was made. The picture was taken on 14 February 1990 as part of a series of 60 images showing the entire solar system with six visible planets. Scientists chose the photo in 2001 as one of the ten best pictures of the space sciences.
Emergence of photos
At the suggestion of the astronomer Carl Sagan, Voyager 1 was shot after completion of the primary mission objectives by 180 degrees and took on the series of 39 wide-angle and telephoto shooting 21. The probe was located away from the sun and 32 degrees above the ecliptic, that is looked at from above the solar system at the time of recording about 6 to 7 billion kilometers. On the collage can be seen from left to right: Jupiter, the Earth, Venus, the Sun, Saturn, Uranus and Neptune. Mercury and Pluto are not visible in the photo, because they were too small, as they had from the cameras can be recorded. The Mars was located at the time of shooting too close to the sun and was outshone by this.
The earth was taken with a vidicon camera with telephoto lens. The camera has seven color filters, this image of the blue, green and violet filters were used. The leading through the image rays emerged as scattering of sunlight on the camera lens, as this was not designed to be aimed directly at the sun. The earth takes only a 12 % of a single pixel.
The wide angle view of the sun was recorded with the darkest filter and the shortest possible exposure time (5 /1000 seconds ), in order to avoid over-exposure. The sun had seen the record time is only 1/ 40 of the apparent diameter as seen from the Earth. However, it was still 8 million times brighter than the next brightest star Sirius.
After completion of the shooting, the camera systems Voyager were switched off to save energy and space. The necessary technology on earth to interpret the image data from Voyager has also been lowered.
The following table has been calculated with the HORIZONS software system.
Book and considerations of Carl Sagan
The image inspired Sagan to his book Pale Blue Dot: A Vision of the Human Future in Space ( German Title: Pale Blue Dot Our home universe. ). Carl Sagan, who had already with the book and the television series Cosmos: A Personal Voyage ( German title: Our cosmos ) had brought closer to a broad public complex scientific issues such as the origin of the universe, the galaxy, and of life, mixed in this book philosophical reflections on the position of man in the universe with observations on contemporary knowledge about our solar system. In addition, there are video collagen, which were lined with sound recording by Carl Sagan.