Numbers, please! Last image of the earth from 6 billion kilometers away

"Pale Blue Dot" – one of the last photos taken by Voyager 1 – is still the most distant image of the Earth. Astronomer Carl Sagan provided the idea.

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Feb 18, 2025 at 3:11 pm CET

7 min. read

By

Markus Will

At first glance, the photo taken by Voyager 1 35 years ago appears unspectacular: Earth can be considered a tiny dot of light from a distance of 6.055 billion kilometers. And yet, this image shows like no other how small and fragile the only human habitat to date appears from space.

The image, called “Pale Blue Dot”, was part of a series of 60 photos taken on February 14, 1990, with which the space probe, launched in 1977, photographed various planets in their orbits around the sun. The idea for this “family portrait” came from US astronomer Carl Sagan.

In this section, we present amazing, impressive, informative and funny figures ("Zahlen") from the fields of IT, science, art, business, politics and, of course, mathematics every Tuesday. The wordplay "Zahlen, bitte!" for a section about numbers is based on the ambiguity of the German word "Zahlen." On one hand, "Zahlen" can be understood as a noun in the sense of digits and numerical values, which fits the theme of the section. On the other hand, the phrase "Zahlen, bitte!" is reminiscent of a waiter's request in a restaurant or bar when they are asked to bring the bill. Through this association, the section acquires a playful and slightly humorous undertone that catches the readers' attention and makes them curious about the presented numbers and facts.

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Sagan had been a consultant to the US space agency NASA since the 1950s. Among other things, he prepared the Apollo astronauts for their flights to the moon. As a guest scientist at the Jet Propulsion Laboratory, which builds and operates satellites and space probes for NASA, Sagan was involved in various Mariner and Viking missions. He was also a key advisor on Voyager 1 and Voyager 2, which visited some outer planets of the solar system.

Black and white picture of Dr. Carl Sagan with dark, long hair. He stands in front of several pictures of Mars hanging on a wall and points to one. He is wearing a gray turtleneck sweater and black trousers. — Carl Sagan, * November 9, 1934 in Brooklyn, New York; † December 20, 1996 in Seattle, Washington, was an astronomer, astrophysicist, presenter and author. He not only advised NASA, but also communicated scientific topics in various TV programs and with his non-fiction books. He died in 1996 at the age of 62 from the bone marrow disease myelodysplastic syndrome.

(Image: NASA/JPL-Caltech)

Recording the planetary family with the last images

As a member of the Voyager Image Team – which analyzed and published the images from the two space probes – he had the idea in 1981 that one of the two Voyager probes could image the Earth. He suspected that the Earth, as a tiny dot, might not be as spectacular as other Voyager images, but that this tininess of our home planet could have an even more impressive effect on the viewer.

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The Voyager missions took advantage of a favorable planetary constellation that only occurs every 176 years, allowing a space probe to visit the four outer gas giants one after the other. While Voyager 2 visited all the gas giants, the team steered Voyager 1 past Saturn's moon Titan because the moon was an interesting target in the search for extraterrestrial life. However, Voyager 1 was no longer able to reach Saturn, Uranus, and Neptune as Voyager 2 did during the “Grand Tour”.

A section of a space photograph. Some radiant image artifacts can be seen, in it is a tiny bright dot - Our Earth. — You could almost miss it, the white dot in the middle of an image artifact. This is the Earth from a distance of 6 billion kilometers. The image was taken by Voyager 1 on February 14, 1990.

(Image: NASA/JPL)

Voyager 1 therefore moved away from the ecliptic plane (the apparent axis of the planets around the sun) after the flyby, making it ideal for the photo series of the planets. From the point of view of Voyager 2, whose trajectory remained much closer to the planets' orbits, Jupiter was too close to the Sun, so there was a risk that sensitive instruments could be damaged when taking pictures with incorrect exposures.

Last Voyager image series in 32 minutes

On February 14, 1990, Voyager 1 was at a distance of 45.5 astronomical units (about 6.055 billion kilometers) and 32 degrees above the ecliptic. The probe rotated 180 degrees and warmed up the cameras for about three hours. The Voyager team pointed the cameras at Neptune at 04:48 GMT and took a series of images of other celestial bodies such as Uranus, Saturn, Mars, the Sun, Jupiter, Earth, and Venus in 34 minutes. After 39 wide-angle images and 21 images with narrower angles, the task was complete.

Schematic representation of Voyager 1 on February 14, 1990, showing the individual planets in their orbits around the sun, and the flight path and position of Voyager 1 in relation to them. — (Image: Nagualdesign:Joe Haythornthwaite and Tom Ruen, CC BY-SA 4.0)

The images for the “family portrait” were the last photos taken by Voyager 1: The cameras were then switched off for good. Voyager 1 had completed its primary tasks and from then on, the probe, like Voyager 2, would no longer fly to objects. From now on, the focus was on saving energy so that the probes could be operated for as long as possible. The images were stored on a 328 m long magnetic tape. Voyager transmitted the series of images to Earth in four phases. On May 1, 1990, all 60 images were transmitted.

The scientists at JPL processed the images into a collage of our solar system. The image of the Earth called “Blue Pale Dot” in particular attracted a lot of attention. To this day, it is the image of the Earth taken from the greatest distance. Jurrie van der Woude, who worked at JPL for 37 years, once said about the significance of Pale Blue Dot: “Scientifically, it didn't help us. But historically, it is priceless. It was the first time our species had been so far from home and could turn around and look back at our own neighborhood.” Of the more than 67,000 images transmitted to Earth by the two Voyager probes, Blue Pale Dot was ideally one of the most important.

The "family portrait": 60 individual images of most of the planets in our solar system as they orbit the probe. Taken on February 14, 1990, 32 degrees above the ecliptic.

Inspiration for Sagan's last book

Carl Sagan published the book “Pale Blue Dot: A Vision of the Human Future in Space” in 1994. For him, this picture showed how humanity overestimates itself too much: “From this distant point of view, Earth may not seem particularly interesting. But it's different for us. Look at this point again. This is here. This is our home. This is us. This is where everyone you love, everyone you know, everyone you've ever heard of, everyone who's ever existed, has spent their lives.”

“Our attitude, our conceited self-importance, the delusion that we occupy a privileged position in the universe, is challenged by this pale point of light. Our planet is a lonely speck in the great, all-enveloping cosmic darkness. In our darkness, in all this vastness, there is no indication that help will come from elsewhere to save us from ourselves. Earth is the only world so far known to harbor life. There is no other place, at least in the near future, to which our species could emigrate.”

The image inspired the creators of the Cassini-Huygens Saturn mission in 2013 to name an image of Earth next to Saturn as “Cassini's Pale Blue Dot”. To mark the 30th anniversary, NASA published an edited version of the Blue Pale Dot image in 2020, using modern image processing techniques to make the Earth more visible while respecting the work of the original editors.

You can see the revised version of the Blue Pale Dot image. It is again a space image, this time with a higher blue component. A bright dot can be seen in an image artifact: The Earth. — The revised version of the Blue Pale Dot released in 2020. The colors have been reworked, it looks brighter and bluer. The earth can be seen as a white dot in an image artifact.

Two sentences by Carl Sagan about the Blue Pale Dot seem more relevant than ever: “It has been said that astronomy is a humbling and character-building experience. There is perhaps no better proof of the folly of human imagination than this distant image of our tiny world. To me, it underscores our responsibility to be kinder to one another and to preserve and nurture the pale blue dot, the only home we have ever known.”