''Pale Blue Dot'' is a
photograph
A photograph (also known as a photo, or more generically referred to as an ''image'' or ''picture'') is an image created by light falling on a photosensitivity, photosensitive surface, usually photographic film or an electronic image sensor. Th ...
of
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
taken on February 14, 1990, by the ''
Voyager 1
''Voyager 1'' is a space probe launched by NASA on September 5, 1977, as part of the Voyager program to study the outer Solar System and the interstellar medium, interstellar space beyond the Sun's heliosphere. It was launched 16 days afte ...
''
space probe
Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which th ...
from an unprecedented distance of over kilometers ( miles, 40.5
AU), as part of that day's
''Family Portrait'' series of images of the
Solar System
The Solar SystemCapitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Sola ...
.
In the photograph, Earth's
apparent size is less than a
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a Raster graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...
; the planet appears as a tiny dot against the vastness of
space
Space is a three-dimensional continuum containing positions and directions. In classical physics, physical space is often conceived in three linear dimensions. Modern physicists usually consider it, with time, to be part of a boundless ...
, among bands of sunlight reflected by the camera.
Commissioned by
NASA
The National Aeronautics and Space Administration (NASA ) is an independent agencies of the United States government, independent agency of the federal government of the United States, US federal government responsible for the United States ...
and resulting from the advocacy of astronomer and author
Carl Sagan
Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist and science communicator. His best known scientific contribution is his research on the possibility of extraterrestrial life, including e ...
, the photograph was interpreted in Sagan's 1994 book, ''
Pale Blue Dot'', as representing humanity's minuscule and ephemeral place amidst the cosmos.
''Voyager 1'' was launched on September 5, 1977, with the initial purpose of studying the outer Solar System. After fulfilling its primary mission and as it ventured out of the Solar System, the decision to turn its camera around and capture one last image of Earth emerged, in part due to Sagan's proposition.
[
]
Over the years, the photograph has been revisited and celebrated on multiple occasions, with NASA acknowledging its anniversaries and presenting updated versions, enhancing its clarity and detail.
Background
''Voyager 1'' is a
robotic spacecraft
Uncrewed spacecraft or robotic spacecraft are spacecraft without people on board. Uncrewed spacecraft may have varying levels of autonomy from human input, such as remote control, or remote guidance. They may also be autonomous, in which t ...
on a mission to study the outer Solar System and eventually
interstellar space.
After
encountering the Jovian system in 1979 and the
Saturnian system
The moons of Saturn are numerous and diverse, ranging from tiny moonlets only tens of meters across to the enormous Titan (moon), Titan, which is larger than the planet Mercury (planet), Mercury. There are 274 natural satellite, moons with con ...
in 1980, the primary mission was declared complete in November of the same year. ''Voyager 1'' was the first space probe to provide detailed images of the two largest planets and their major
moons.

The spacecraft, still traveling at , is the most distant human-made object from Earth and the first to leave the Solar System.
Its mission has been extended and continues to this day, with the aim of investigating the
boundaries of the Solar System, including the
Kuiper belt
The Kuiper belt ( ) is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. It is similar to the asteroid belt, but is far larger—20 times ...
, the
heliosphere
The heliosphere is the magnetosphere, astrosphere, and outermost atmospheric layer of the Sun. It takes the shape of a vast, tailed bubble-like region of space. In plasma physics terms, it is the cavity formed by the Sun in the surrounding ...
and
interstellar space. Since its launch, it receives routine commands and transmits data back to the
Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA' ...
.
''Voyager 1'' was expected to work only through the Saturn
Saturn is the sixth planet from the Sun and the second largest in the Solar System, after Jupiter. It is a gas giant, with an average radius of about 9 times that of Earth. It has an eighth the average density of Earth, but is over 95 tim ...
encounter. When the spacecraft passed the planet in 1980, astronomer and author Carl Sagan
Carl Edward Sagan (; ; November 9, 1934December 20, 1996) was an American astronomer, planetary scientist and science communicator. His best known scientific contribution is his research on the possibility of extraterrestrial life, including e ...
proposed the idea of the space probe taking one last picture of Earth. He acknowledged that such a picture would not have had much scientific value, as the Earth would appear too small for ''Voyager''s cameras to make out any detail, but it would be meaningful as a perspective on humanity's place in the universe.
Although many in NASA's Voyager program
The Voyager program is an American scientific program that employs two interstellar probes, ''Voyager 1'' and ''Voyager 2''. They were launched in 1977 to take advantage of a favorable planetary alignment to explore the two gas giants Jupiter ...
were supportive of the idea, there were concerns that taking a picture of Earth so close to the Sun risked damaging the spacecraft's imaging system irreparably. It was not until 1989 that Sagan's idea was put in motion, but then instrument calibrations delayed the operation further, and the personnel who devised and transmitted the radio commands to ''Voyager 1'' were also being laid off or transferred to other projects. Richard Truly, the then NASA Administrator, interceded to ensure that the photograph was taken. A proposal to continue to photograph Earth as it orbited the Sun was rejected.
Camera
''Voyager 1''s Imaging Science Subsystem consists of two cameras: a low-resolution wide-angle camera used for spatially extended imaging, and a high-resolution narrow-angle camera intended for detailed imaging of specific targets. Both cameras are slow-scan vidicon
Video camera tubes are devices based on the cathode-ray tube that were used in television cameras to capture television images, prior to the introduction of charge-coupled device (CCD) image sensors in the 1980s. Several different types of tubes ...
tubes with a selenium
Selenium is a chemical element; it has symbol (chemistry), symbol Se and atomic number 34. It has various physical appearances, including a brick-red powder, a vitreous black solid, and a grey metallic-looking form. It seldom occurs in this elem ...
sulphur storage surface, and are fitted with eight colored filters mounted on a filter wheel in front of the tube. ''Pale Blue Dot'' was taken with the narrow-angle camera, a 1500 mm f/8.5 catadioptric cassegrain telescope whose design was based on the 1973 Mariner mission.
The challenge was that, as the mission progressed, the objects to be photographed would increasingly be farther away and would appear fainter, requiring longer exposures and slewing (panning) of the cameras to achieve acceptable quality. The telecommunication capability also diminished with distance, limiting the number of data modes that could be used by the imaging system.
After taking the ''Family Portrait'' series of images, which included ''Pale Blue Dot'', NASA mission managers commanded ''Voyager 1'' to power its cameras down, as the spacecraft was not going to fly near anything else of significance for the rest of its mission, while other instruments that were still collecting data needed power for the long journey to interstellar space.
Photograph
The design of the command sequence to be relayed to the spacecraft and the calculations for each photograph's exposure time were developed by space scientists Candy Hansen of NASA's Jet Propulsion Laboratory
The Jet Propulsion Laboratory (JPL) is a Federally funded research and development centers, federally funded research and development center (FFRDC) in La Cañada Flintridge, California, Crescenta Valley, United States. Founded in 1936 by Cali ...
and Carolyn Porco of the University of Arizona
The University of Arizona (Arizona, U of A, UArizona, or UA) is a Public university, public Land-grant university, land-grant research university in Tucson, Arizona, United States. Founded in 1885 by the 13th Arizona Territorial Legislature, it ...
.[ The command sequence was then compiled and sent to ''Voyager 1'', with the images taken at 04:48 GMT on February 14, 1990.] At that time, the distance between the spacecraft and Earth was 40.47 astronomical unit
The astronomical unit (symbol: au or AU) is a unit of length defined to be exactly equal to . Historically, the astronomical unit was conceived as the average Earth-Sun distance (the average of Earth's aphelion and perihelion), before its m ...
s (6,055 million kilometers, 3,762 million miles).
The data from the camera was stored initially in an on-board tape recorder
An audio tape recorder, also known as a tape deck, tape player or tape machine or simply a tape recorder, is a sound recording and reproduction device that records and plays back sounds usually using magnetic tape for storage. In its present ...
. Transmission to Earth was also delayed by the '' Magellan'' and ''Galileo
Galileo di Vincenzo Bonaiuti de' Galilei (15 February 1564 – 8 January 1642), commonly referred to as Galileo Galilei ( , , ) or mononymously as Galileo, was an Italian astronomer, physicist and engineer, sometimes described as a poly ...
'' missions being given priority use of the Deep Space Network
The NASA Deep Space Network (DSN) is a worldwide Telecommunications network, network of spacecraft communication ground segment facilities, located in the United States (California), Spain (Madrid), and Australia (Canberra), that supports NASA' ...
. Then, between March and May 1990, ''Voyager 1'' returned 60 frames back to Earth, with the radio signal traveling at the speed of light for nearly five and a half hours to cover the distance.
Three of the frames received showed the Earth as a tiny point of light in empty space. Each frame had been taken using a different color filter: blue, green and violet, with exposure times of 0.72, 0.48 and 0.72 seconds respectively. The three frames were then recombined to produce the image that became ''Pale Blue Dot''.
Of the 640,000 individual pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a Raster graphics, raster image, or the smallest addressable element in a dot matrix display device. In most digital display devices, p ...
s that compose each frame, Earth takes up less than one (0.12 of a pixel, according to NASA). The light bands across the photograph are an artifact, the result of sunlight reflecting off parts of the camera and its sunshade, due to the relative proximity between the Sun and the Earth. ''Voyager's'' point of view was approximately 32° above the ecliptic
The ecliptic or ecliptic plane is the orbital plane of Earth's orbit, Earth around the Sun. It was a central concept in a number of ancient sciences, providing the framework for key measurements in astronomy, astrology and calendar-making.
Fr ...
. Detailed analysis suggested that the camera also detected the Moon
The Moon is Earth's only natural satellite. It Orbit of the Moon, orbits around Earth at Lunar distance, an average distance of (; about 30 times Earth diameter, Earth's diameter). The Moon rotation, rotates, with a rotation period (lunar ...
, although it is too faint to be visible without special processing.
''Pale Blue Dot'', which was taken with the narrow-angle camera, was also published as part of a composite picture created from a wide-angle camera photograph showing the Sun and the region of space containing the Earth and Venus. The wide-angle image was inset with two narrow-angle pictures: ''Pale Blue Dot'' and a similar photograph of Venus. The wide-angle photograph was taken with the darkest filter (a methane absorption band) and the shortest possible exposure (5 milliseconds), to avoid saturating the camera's vidicon tube with scattered sunlight. Even so, the result was a bright burned-out image with multiple reflections from the optics in the camera and the Sun that appears far larger than the actual dimension of the solar disk. The rays around the Sun are a diffraction pattern of the calibration lamp which is mounted in front of the wide-angle lens.[
]
Pale blue color
Earth appears as a blue dot in the photograph primarily because of Rayleigh scattering
Rayleigh scattering ( ) is the scattering or deflection of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scat ...
of sunlight
Sunlight is the portion of the electromagnetic radiation which is emitted by the Sun (i.e. solar radiation) and received by the Earth, in particular the visible spectrum, visible light perceptible to the human eye as well as invisible infrare ...
in its atmosphere. In Earth's air, short-wavelength visible light such as blue light is scattered to a greater extent than longer wavelength light such as red light, which is the reason why the sky appears blue from Earth. (The ocean also contributes to Earth's blueness, but to a lesser degree than scattering.) Earth is a ''pale'' blue dot, rather than dark blue, because white light reflected by clouds combines with the scattered blue light.
Earth's reflectance
The reflectance of the surface of a material is its effectiveness in reflecting radiant energy. It is the fraction of incident electromagnetic power that is reflected at the boundary. Reflectance is a component of the response of the electronic ...
spectrum from the far-ultraviolet to the near-infrared
Infrared (IR; sometimes called infrared light) is electromagnetic radiation (EMR) with wavelengths longer than that of visible light but shorter than microwaves. The infrared spectral band begins with the waves that are just longer than those of ...
is unlike that of any other observed planet and is partially due to the presence of life on Earth. Rayleigh scattering, which causes Earth's blueness, is enhanced in an atmosphere that does not substantially absorb visible light, unlike, for example, the orange-brown color of Titan
Titan most often refers to:
* Titan (moon), the largest moon of Saturn
* Titans, a race of deities in Greek mythology
Titan or Titans may also refer to:
Arts and entertainment
Fictional entities
Fictional locations
* Titan in fiction, fictiona ...
, where organic haze particles absorb strongly at blue visible wavelengths. Earth's plentiful atmospheric oxygen, which is produced by photosynthetic
Photosynthesis ( ) is a Biological system, system of biological processes by which Photoautotrophism, photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical ener ...
life forms, oxidizes organics in the atmosphere and converts them to water and carbon dioxide, causing the atmosphere to be transparent to visible light and allowing for substantial Rayleigh scattering and hence stronger reflectance of blue light.
Reflections
In his 1994 book, '' Pale Blue Dot'', Carl Sagan comments on what he sees as the greater significance of the photograph, writing:
Anniversaries
In 2015, NASA acknowledged the 25th anniversary of the photograph. Ed Stone, Voyager project scientist, commented: "Twenty-five 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."
In 2020, for the image's 30th anniversary, NASA published a new version of the original ''Voyager'' photo: ''Pale Blue Dot Revisited'', obtained using modern image processing techniques "while attempting to respect the original data and intent of those who planned the images." Brightness levels and colors were rebalanced to enhance the area containing the Earth, and the image was enlarged, appearing brighter and less grainy than the original. The direction of the Sun is toward the bottom, where the image is brightest.
To celebrate the same occasion, the Carl Sagan Institute released a video with several noted astronomers reciting Sagan's "Pale Blue Dot" speech.
See also
* List of photographs considered the most important
This is a list of photographs considered the most important in surveys where authoritative sources review the history of the medium not limited by time period, region, genre, topic, or other specific criteria. These images may be referred to as t ...
* 2010 ''Family Portrait''
* Bluedot Festival
* Early Earth, or "pale orange dot"
* ''Earthrise
''Earthrise'' is a photograph of Earth and part of the Moon's surface that was taken from lunar orbit by astronaut William Anders on December 24, 1968, during the Apollo 8 mission. Nature photographer Galen Rowell described it as "the most in ...
''
* Overview effect
The overview effect is a cognitive shift reported by some astronauts while viewing the Earth from outer space, space. Researchers have characterized the effect as "a state of awe with self-transcendence, self-transcendent qualities, precipitated b ...
* Space selfie
* ''The Blue Marble
''The Blue Marble'' is a photograph of Earth taken on December 7, 1972, by either Ronald Evans (astronaut), Ron Evans or Harrison Schmitt aboard the Apollo 17 spacecraft on its way to the Moon. Viewed from around from Earth's surface, a crop ...
''
* The Day the Earth Smiled
* Timeline of first images of Earth from space
Photography and other imagery of planet Earth from outer space started in the 1940s, first from rockets in suborbital flight, subsequently from satellites around Earth, and then from spacecraft beyond Earth's orbit.
Timeline
See also
* L ...
References
Further reading
*
*
External links
Audio recording
of Carl Sagan reading from ''Pale Blue Dot'' (US Library of Congress
The Library of Congress (LOC) is a research library in Washington, D.C., serving as the library and research service for the United States Congress and the ''de facto'' national library of the United States. It also administers Copyright law o ...
)
Sagan's rationale for human spaceflight
– Article in '' The Space Review''
Video produced for Pangea Day
with Sagan reading from ''Pale Blue Dot''
*
*
Cassini's Pale Blue Dot
– European Space Agency
The European Space Agency (ESA) is a 23-member International organization, international organization devoted to space exploration. With its headquarters in Paris and a staff of around 2,547 people globally as of 2023, ESA was founded in 1975 ...
{{Authority control
1990 in art
1990 works
1990s photographs
Color photographs
February 1990
Photographs of Earth from outer space
Voyager program