The cameras of Voyager 1 on February 14, 1990, pointed back toward the Sun and took a series of pictures of the Sun, Earth and other planets, making the first ever ‘family portrait’ of the Solar System as seen from the outside.
It was on February 14, 1990, that the Voyager 1 spacecraft looked back at the Solar System and snapped the first-ever pictures of the planets from its perch at that time beyond Neptune. The insets show the planets magnified many times. Image credit: NASA / JPL-Caltech.
In the course of taking this mosaic consisting of a total of 60 frames, Voyager 1 made several images of the inner Solar System from a distance of 40 astronomical units (1 AU = 150 million km) and about 32 degrees above the ecliptic plane. 39 wide angle frames link together six of the planets of our Solar System in this mosaic.
Our Sun is seen as the bright object in the center of the circle of frames. Outermost Neptune is 30 times further from the Sun than Earth.
The wide-angle image of the Sun was taken with the camera’s darkest filter and the shortest possible exposure to avoid saturating the camera’s vidicon tube with scattered sunlight.
The Sun is not large as seen from Voyager 1, only about 1/14 of the diameter as seen from our planet, but is still almost 8 million times brighter than the brightest star in Earth’s sky, Sirius.
The result of this great brightness is an image with multiple reflections from the optics in the camera. Wide-angle images surrounding the Sun also show many artifacts attributable to scattered light in the optics. These were taken through the clear filter with one second exposures.
Narrow-angle images of Earth, Venus, Jupiter, Saturn, Uranus and Neptune were acquired as the spacecraft built the wide-angle mosaic.
Jupiter is larger than a narrow-angle pixel and is clearly resolved, as is Saturn with its rings.
Uranus and Neptune appear larger than they really are because of image smear due to spacecraft motion during the long exposures.
From Voyager’s great distance Earth and Venus are mere points of light, less than the size of a picture element even in the narrow-angle camera. Earth was a crescent only 0.12 pixel in size.
Coincidentally, Earth lies right in the center of one of the scattered light rays resulting from taking the image so close to the Sun.
A few key members did not make it in: Mars had little sunlight, Mercury was too close to the Sun, and dwarf planet Pluto turned out too dim.
Taking these images was not part of the original plan, but the late Carl Sagan, a member of the Voyager imaging team at the time, had the idea of pointing the spacecraft back toward its home for a last look.
The title of his 1994 book Pale Blue Dot refers to the image of Earth in this series.
This color image of the Earth, dubbed Pale Blue Dot, is a part of the first ever ‘family portrait’ of our Solar System taken by Voyager 1. Image credit: NASA / JPL-Caltech.
“25 years ago, Voyager 1 looked back toward Earth and saw a pale blue dot, an image that continues to inspire wonderment about the spot we call home,” said Dr Ed Stone from the California Institute of Technology in Pasadena, who is a project scientist for the Voyager mission.
These images are the last that Voyager 1, which launched in 1977, returned to Earth.
NASA scientists subsequently turned the camera off so that the computer controlling it could be repurposed.
The spacecraft is still operating, but no longer has the capability to take images.
“After taking these images in 1990, we began our interstellar mission. We had no idea how long the spacecraft would last,” Dr Stone said.
Today, Voyager 1, at a distance of 130 astronomical units, is the farthest human-made object from Earth, and it still regularly communicates with our planet.
In August 2012, the spacecraft entered interstellar space – the space between the stars – and has been delivering data about this uncharted territory ever since.
Its twin, Voyager 2, also launched in 1977, is also journeying toward interstellar space.
Sagan wrote in his Pale Blue Dot book: “That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives…”
“There is perhaps no better demonstration of the folly of human conceits than this distant image of our tiny world.”
