NASA Voyager-1: On the edge of the Solar System

Artist's concept of NASA's Voyager spacecraft. 

Credit: NASA/JPL-Caltech 

Data from NASA's Voyager 1 spacecraft continues to provide new insight on the outskirts of our solar system, a frontier thought to be the last that Voyager will cross before becoming the first man-made object to reach interstellar space.

In papers published this week in the journal Science, scientists from the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., and other Voyager partner institutions provide more clarity on the region they named the "magnetic highway" in December 2012.

Cruising through what scientists describe as a curious, unexpected charged-particle environment, Voyager has detected, for the first time, low-energy galactic cosmic rays, now that particles of the same energy from inside the bubble around our Sun disappeared.

As a result, Voyager now sees the highest level so far of particles from outside our solar bubble that originate from the death of other nearby stars.

"Voyager 1 may be months or years from leaving the solar system—we just don't know," says APL's Stamatios Krimigis, principal investigator for Voyager's Low-Energy Charged Particle (LECP) instrument.

"But the wait itself is incredibly exciting, since Voyager continues to defy predictions and change the way we think about this mysterious and wonderful gateway region to the galaxy."

This artist's concept shows NASA's Voyager 1 spacecraft exploring a region called the "depletion region" or "magnetic highway" at the outer limits of our heliosphere, the bubble the sun blows around itself. 

In this region, the magnetic field lines generated by our sun (yellow arcs) are piling up and intensifying and low-energy charged particles that are accelerated in the heliosphere's turbulent outer later (green dots) have disappeared. 

Scientists think the depletion region is the last region Voyager 1 has to cross before reaching interstellar space, which is the space between stars, Voyager 1 passed a shockwave known as the termination shock in 2004, where solar wind suddenly slowed down and became turbulent. 

In 2010, it then passed into an area called the "stagnation region" where the outward velocity of the solar wind slowed to zero and sporadically reversed direction. 

In the slow-down and stagnation regions, the prevalence of low-energy charged particles from our heliosphere jumped dramatically and is indicated by the green dots. 

On Aug. 25, 2012. Voyager 1 entered the depletion or magnetic highway region, where the magnetic field acts as a kind of "magnetic highway" allowing energetic ions from inside the heliosphere to escape out, and cosmic rays from interstellar space zoom in. 

Magnetic field lines form a spiral around the solar system because of the rotation of the sun, and at the edge of the heliosphere they form roughly parallel arcs. 

Because an interstellar wind outside is pushing back on the heliosphere, magnetic field lines pile up as the solar wind slows, like cars back up at a freeway off-ramp. 

The compression of field lines increases the strength of the magnetic field as Voyager approaches interstellar space. 

Since scientists don't know the exact location of the heliopause - which is the border to interstellar space - that area has been labeled with a question mark. 

Image credit: NASA/JPL-Caltech 

Voyager 1 and 2 were launched in 1977 and between them visited Jupiter, Saturn, Uranus and Neptune.

Since 1990, the twin spacecraft have been on their Interstellar Mission, on track to leave the heliosphere, which is the bubble of magnetic field and charged particles the Sun blows around itself.

On Aug. 25, 2012, when Voyager 1 was about 11 billion miles (18 billion kilometers) from the Sun, the spacecraft reached the so-called magnetic highway where charged particles from inside the heliosphere zoomed out along the magnetic field as cosmic rays from far outside zoomed in.

The lack of a detectable change in the direction of that magnetic field, however, convinced scientists that Voyager remained within the Sun's influence.

The new Science papers focus on observations from the summer and fall of 2012 by LECP as well as Voyager 1's Cosmic Ray and Magnetometer instruments, with additional LECP data through April 2013.

More information: References:

* "Magnetic Field Observations as Voyager 1 Entered the Heliosheath Depletion Region," L. F. Burlaga, N. F. Ness, and E. C. Stone, Science, DOI: 10.1126/science.1235451; www.sciencemag.org/content/early/2013/06/26/science.1235451.abstract 
* "Search for the Exit: Voyager 1 at Heliosphere's Border with the Galaxy," S. M. Krimigis, R. B. Decker, E. C. Roelof, M. E. Hill, T. P. Armstrong, G. Gloeckler, D. C. Hamilton, and L. J. Lanzerotti, Science, DOI:10.1126/science.1235721; www.sciencemag.org/content/early/2013/06/26/science.1235721.abstract 
* "Voyager 1 Observes Low-Energy Galactic Cosmic Rays in a Region Depleted of Heliospheric Ions," E. C. Stone, A. C. Cummings, F. B. McDonald, B. C. Heikkila, N. Lal, and W. R. Webber, Science, DOI:10.1126/science.1236408; www.sciencemag.org/content/early/2013/06/26/science.1236408.abstract

Carl Sagan's Pale Blue Dot, Animated in Motion Graphics

“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.”

Over the years, I’ve enjoyed my share of animated adaptations of Carl Sagan’s iconic Pale Blue Dot monologue, based on the seminal photograph of Earth taken by the Voyager 1 spacecraft in 1990. Now comes a lovely motion graphics adaptation by animation studio ORDER — enjoy, and see if you can hold back the chills.

NASA Voyager-1 and Humankind set to cross the final frontier to Interstellar Space

It will be one of the most important milestones in human history as, for the first time, an ambassador for humankind moves beyond the confines and protection of our solar system.

NASA scientists are preparing for the moment, any day now, when the first of two spacecraft launched in the late 1970s crosses the invisible boundary that marks the start of "interstellar space".

Already they have passed some of the furthest planets of the solar system, transmitting spectacular images of the worlds that circle the sun.

This artist's concept by NASA/JPL-Caltech shows Voyager 1 and Voyager 2 at the edge of the solar system. 

The Voyager 1 probe, which is now about 17.7 billion kilometres from Earth, has entered a "transition zone" at the edge of the solar system, scientists say.  

Photo: AFP/NASA/JPL-Caltech

Voyager 1 is about 11 billion miles from Earth and hurtling away at a rate of 13 kilometres a second. Its sister craft, Voyager 2, is not far behind.

Each carries an array of instruments to gather information about outer space - and also a gold-plated copper disc with sounds and images intended to convey a sample of what life is like on Earth should they ever encounter other intelligent life.

Should an alien ever find one of the craft, the first human to whom they will be introduced - assuming they can decode the technology - will be Ann Druyan, now 63, an author and television producer who fell in love with the US astronomer Dr Carl Sagan while they were working on the Voyager mission.

A file photo released by NASA in 1970 shows the golden record on Voyager 1, launched on September 5, 1977, with a cartridge and a needle to play it.  

Photo: AFP/NASA

"Mars Belongs to the Martians" - Carl Sagan on Exploitation

There are so many examples of human misuse of the Earth that even phrasing this question chills me. If there is life on Mars, I believe we should do nothing with Mars. Mars then belongs to the Martians, even if the Martians are only microbes. The existence of an independent biology on a nearby planet is a treasure beyond assessing, and the preservation of that life must, I think, supersede any other possible use of Mars.

Carl Sagan’s gentle warning to future Mars explorers

Neil deGrasse Tyson - We Stopped Dreaming (Episode 1) - YouTube

Voyager Instrument Cooling Rapidly: Heater Turned off

To decisively reduce power consumption, mission managers have turned off a heater on part of NASA's Voyager 1 spacecraft, dropping the temperature of its ultraviolet spectrometer instrument more than 23 degrees Celsius (41 degrees Fahrenheit).

It is now operating at a temperature below minus 79 degrees Celsius (minus 110 degrees Fahrenheit), the coldest temperature that the instrument has ever endured.

This heater shut-off is a step in the careful management of the diminishing electrical power so that the Voyager spacecraft can continue to collect and transmit data through 2025.

At the moment, the spectrometer continues to collect and return data.

It was originally designed to operate at temperatures as low as minus 35 degrees Celsius (minus 31 degrees Fahrenheit), but it has continued to operate in ever chillier temperatures as heaters around it have been turned off over the last 17 years.

It was not known if the spectrometer would continue working, but since 2005, it has been operating at minus 56 degrees Celsius (69 degrees Fahrenheit.) So engineers are encouraged that the instrument has continued to operate, even after the nearby heater was turned off in December.

(The spectrometer is likely operating at a temperature somewhat lower than minus 79 degrees Celsius, or minus 110 degrees Fahrenheit, but the temperature detector does not go any lower.)

Scientists and mission managers will continue to monitor the spectrometer's performance.

It was very active during Voyager 1's encounters with Jupiter and Saturn, and since then an international team led by scientists in France has been analyzing the spectrometer's data.

This latest heater shut-off was actually part of the nearby infrared spectrometer, which itself has not been operational on Voyager 1 since 1998.

Carl Sagan inspired Art

When she lost her friend Cathy to cancer, artist Michele Banks set out to tell her friend’s story in the language she speaks most fluently and eloquently: painting. But she didn’t want it to be another “cancer painting.”

Instead, she found unlikely inspiration at the intersection of the deadly disease and Carl Sagan’s iconic, life-affirming idea that we’re all made of “star stuff” — she saw a striking parallel between supernovas and dividing cancer cells. The result is simply breathtaking.

I was reading about astronomer Carl Sagan, who often expressed the idea that humans are made of “star stuff”. That is, that all the basic elements of life on earth derive from “space debris” from the gigantic explosions of massive, ancient stars. This concept is at once so simple and so mind-boggling that it’s a struggle to absorb, much less to express artistically. I started looking around for ideas of how to visually portray the basic elements such as hydrogen, helium and nitrogen. Um. This is difficult, because you can’t see them. If you do a Google image search on Carbon, it comes up with a lot of gray-black cars. But when I thought about how the elements were released, I found supernovas. Not only are supernovas beautiful and awe-inspiring, they bear a strong resemblance to dividing cells, especially explosively dividing cancer cells.” ~ Michele Banks

Curiously, Sagan himself also had myelodysplastic syndrome, or “preleukemia,” and underwent three bone marrow transplants before losing the long and difficult fight in 1996. Banks reflects:

This painting, besides celebrating the cosmic connection that all living creatures share, goes out to Cathy and Carl. From the infinitely tiny cells deep in the marrow of their bones, to the billions of stars in the sky.”

You can find Banks on Twitter and her beautiful prints on Etsy.

Carl Sagan and the Blue Dot

Click on the picture to play the GIF!

NASA's Voyager Probes to Leave Solar System by 2016

A long history of exploration
Voyager 2 was launched on Aug. 20, 1977, and its twin Voyager 1 blasted off a few weeks later, on Sept 5. Both spacecraft were tasked mainly with studying Jupiter, Saturn and their moons.

The spacecraft are also carrying so-called "golden records" containing the distilled essences of humanity, such as various musical offerings and greetings to the universe in 55 different languages. The goal is to teach alien civilizations a little about us, should they ever pluck the Voyagers out of the void. (SETI)

In their early years, the Voyagers made a series of important discoveries about the giant planets. For example, the mission detected active volcanoes on Jupiter's moon Io – the first time such features were found beyond Earth. The spacecraft also found evidence of a liquid-water ocean beneath the icy surface of Jupiter's moon Europa.

"Each of these discoveries changed the way we thought of other worlds," Stone said in a statement.

The Voyagers made it past Saturn, with the spacecraft examining Neptune and Uranus as well. And then they just kept on going, zooming toward the edge of the solar system in different directions and different planes.

Voyager 1 is now about 11 billion miles (17.7 billion kilometers) from Earth, while Voyager 2 is about 9 billion miles (14.5 billion km) away, Stone said. Voyager 1 is the most far-flung human-made object in the universe. [NASA's 10 Greatest Science Missions]

Probing the heliosheath
While the Voyagers have left the planets well behind, they're not beyond the solar system yet.

They're still within a huge bubble called the heliosphere, which is made of solar plasma and solar magnetic fields. This gigantic structure is about three times wider than the orbit of Pluto, researchers said.

Specifically, the Voyagers are plying the heliosphere's outer shell, a turbulent region called the heliosheath.

"We're smelling, we're touching the ionized matter in the heliosheath," said Merav Opher of Boston University, a Voyager guest investigator.

The Voyagers are helping scientists better understand the mysterious heliosphere. For example, measurements from the spacecraft revealed that the structure is distorted and asymmetric, yanked out of shape by the interstellar magnetic field, researchers said.

And in June 2010, Voyager 1 measured the outward velocity of the solar wind -- the million-mile-per-hour stream of charged particles coming from the sun -- to be zero in its location in the heliosheath. That surprising reading hasn't changed since.

Researchers don’t think the solar wind has stopped out there; they believe it may have just turned a corner. So they've recently started ordering Voyager 1 to do a series of acrobatic maneuvers, to point its instruments in different directions so the craft can pick up and track the puzzling solar breeze.

Breaking free
The heliosheath looks to be about 3 to 4 billion miles (4.8 to 6.4 billion km) thick, and the spacecraft are already well into it. Based on their speed, they should be out in about five years, Stone said.

That time frame is manageable. The Voyagers' radioisotope thermoelectric generators -- which convert the heat emitted by plutonium's radioactive decay into electricity -- can power their instruments until at least 2020. And the spacecraft have enough hydrazine fuel left to perform maneuvers for another 60 years, researchers said.

Of course, there are no signposts marking the start of interstellar space, where the Voyagers will escape the sun's wind and magnetic field only to be buffeted by those of other, far-flung stars. So astronomers will probably have a hard time knowing when the historic moment occurs.

"We are starting to talk about what we expect to see," Stone said. "I suspect, like in the past, we will be surprised, and we may in fact have a debate for a year or two before we finally decide, 'We have crossed the boundary.'"

NASA's Voyager 1 & 2 Spacecraft

NASA's twin Voyager probes were launched in the late 1970s to explore the outer planets in our solar system. But now, nearly 34 years later, the two spacecraft are on their way out of our cosmic neighborhood, knocking on the door of interstellar space.

The spacecraft, called Voyager 1 and Voyager 2, were built by NASA's Jet Propulsion Laboratory in Pasadena, Calif., which continues to operate both. Here are five facts about the two Voyager probes, the longest continuously operating spacecraft in deep space:

1. They're marathon runners
Voyager 2 launched on Aug. 20, 1977, and Voyager 1 launched about two weeks later, on Sept. 5. Since then, the spacecraft have been traveling along different flight paths and at different speeds.
Now about 10.8 billion miles (17.4 billion kilometers) from the sun and hurtling toward interstellar space, Voyager 1 is the farthest human-made object from Earth. Voyager 2 is about 8.8 billion miles (14.2 billion km) from the sun. [NASA's 10 Greatest Science Missions]

2. It takes a while to get ahold of them
Both spacecraft are still sending scientific information about their surroundings through NASA's Deep Space Network. A signal from the ground, traveling at the speed of light, takes about 13 hours one way to reach Voyager 2, and 16 hours to reach Voyager 1.

3. They started out on a grand planetary tour
The primary five-year mission of the Voyagers included the close-up exploration of Jupiter and Saturn, Saturn's rings and the larger moons of the two planets. The mission was extended after a succession of discoveries. [The Solar System Explained: From the Inside Out]

Between them, the two spacecraft have explored all the giant outer planets of our solar system -- Jupiter, Saturn, Uranus and Neptune -- as well as 49 moons, and the systems of rings and magnetic fields those planets possess.

The current mission, the Voyager Interstellar Mission, was planned to explore the outermost edge of our solar system and eventually leave our sun's sphere of influence to enter interstellar space -- the space between the stars.

4. They're carrying messages to aliens
Both Voyager spacecraft carry recorded messages from Earth on golden phonograph records -- 12-inch, gold-plated copper disks. A committee chaired by the late astronomer Carl Sagan (SETI) selected the contents of the records for NASA.

The records are cultural time capsules that the Voyagers bear with them to other star systems. They contain images and natural sounds, spoken greetings in 55 languages and musical selections from different cultures and eras.

5. The Voyagers are blazing new trails
Voyager 1 has reached a distant point at the edge of our solar system, where the outward motion of solar wind ceases. The event is the latest milestone in Voyager 1's passage through the heliosheath, the outer shell of the sun's sphere of influence, before entering interstellar space.

Interstellar space begins at the heliopause, and scientists estimate Voyager 1 will cross this frontier within the next five years.

Mountain View SETI Instutute Loses Funding - Mothball Allen Telescope Array

Lacking the money to pay its operating expenses, Mountain View's SETI Institute has pulled the plug on the renowned Allen Telescope Array, a field of radio dishes that scan the skies for signals from extraterrestrial civilizations.

In an April 22 letter to donors, SETI Institute CEO Tom Pierson said that last week the array was put into "hibernation," safe but nonfunctioning, because of inadequate government support.

The timing couldn't be worse, say SETI scientists. After millenniums of musings, this spring astronomers announced that 1,235 new possible planets had been observed by Kepler, a telescope on a space satellite.

They predict that dozens of these planets will be Earth-sized -- and some will be in the "habitable zone," where the temperatures are just right for liquid water, a prerequisite of life as we know it.

"There is a huge irony," said SETI Director Jill Tarter, "that a time when we discover so many planets to look at, we don't have the operating funds to listen."

SETI senior astronomer Seth Shostak compared the project's suspension to "the Niña, Pinta and Santa Maria being put into dry dock. "...

This is about exploration, and we want to keep the thing operational. It's no good to have it sit idle.

"We have the radio antennae up, but we can't run them without operating funds," he added. "Honestly, if everybody contributed just 3 extra cents on their 1040 tax forms, we could find out if we have cosmic company."

The SETI Institute's mission is to explore the origin, nature and prevalence of life in the universe. This is a profound search, it believes, because it explains our place among the stars.

The program, located on U.S. Forest Service land near Mount Lassen, uses telescopes to listen for anything out of the ordinary -- a numerical sequence of "beeps," say, or crackly dialogue from an alien version of a disembodied "Charlie" talking to his "Angels." The entire program was set up to prove what once seemed unthinkable: In the universe, we are not alone.

Lack of funding
But funding for SETI has long been a headache for E.T.-seekers. NASA bankrolled some early projects, but in 1994, Sen. Richard Bryan of Nevada convinced Congress that it wasn't worth the cost, calling it the "Great Martian Chase" and complaining that not a single flying saucer had applied for FAA approval.

However, successful private funding came from donors such as Microsoft co-founder Paul Allen, allowing SETI to raise $50 million to build the 42 dishes.

Plans called for construction of 350 individual radio antennas, all working
in concert. But what's lacking now is funding to support the day-to-day costs of running the dishes.

This is the responsibility of UC Berkeley's Radio Astronomy Laboratory, but one of the university's major funders, the National Science Foundation, supplied only one-tenth its previous support. Meanwhile, the state of California has also cut funding.

About $5 million is needed over the next two years, according to Tarter. She hopes the U.S. Air Force will help, because the array can be used to track satellite-threatening debris in space. But budgets are tight there as well.

Astronomers mourn
The Allen array is not the only radio telescope facility that can be used for SETI searches. But it is the best; elsewhere, scientists have to borrow time on other telescopes.

Meanwhile, other SETI projects will continue, such as the "setiQuest Explorer" (www.setiquest.org), an application that allows citizen scientist volunteers to look for patterns from existing data that might have been missed by existing algorithms. Through a new partnership with "Galaxy Zoo" (www.galaxyzoo.org), this project runs in real time, so discoveries can be followed up on immediately.

Bay Area astronomers mourned the hiatus of the SETI program and expressed concern about the future.

Rob Hawley of the Peninsula Astronomical Society called it "unfortunate. The Allen scope was a wonderful experiment. "... Hubble gets all the press, but there are lots of limitations."

Amateur astronomer Sarah Wiehe of Palo Alto said, "just knowing SETI is there was significant for us. This is a setback."

"If we miss a distant signal," she added, "it would be a terrible loss."

what it means
SETI's mission to explore the prevalence of life in the universe, including about 1,235 possible planets recently discovered, is compromised, according to scientists.

what's next
The program needs about $5 million over the next two years to support the telescope facility.

online extra
To learn more about SETI and its programs, go to www.seti.org 


You can also check out the Guardian article here

Carl Sagan Video - The Frontier is Everywhere

Here We Are: Carl Sagan and the Pale Blue Dot

Carl Sagan - SETI and Planetary Science

Carl Edward Sagan (November 9, 1934 – December 20, 1996) was an American astronomer, astrophysicist, author, cosmologist, and highly successful popularizer of astronomy, astrophysics and other natural sciences.

During his lifetime, he published more than 600 scientific papers and popular articles and was author, co-author, or editor of more than 20 books. In his works, he advocated skeptical inquiry and the scientific method.

He pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI).

Sagan became world-famous for his popular science books and for the award-winning 1980 television series Cosmos: A Personal Voyage, which he narrated and co-wrote.

A book to accompany the program was also published. Sagan also wrote the novel, Contact, the basis for the 1997 film of the same name.

NASA Fixes Bug On Voyager 2

NASA Fixes Bug On Voyager 2

NASA's Voyager 2 spacecraft has resumed sending science data from deep space after engineers fixed a bug that had garbled the information it was sending back to Earth, a leading project scientist said on Monday.
"The science data format is working," Edward Stone told RIA Novosti.

The science data coming from Voyager 2 had been unintelligible since April, but last week engineers at NASA's Jet Propulsion Laboratory in Pasadena, California figured out what was causing the problem - one bit in the memory of the computer that formats the data to transmit it to Earth had flipped from a zero to a one - and reset the system.

After three days of monitoring the engineering data to ensure the fix was successful, the command to restart science data transmission was sent to the spacecraft on Saturday. It takes nearly 13 hours for a radio signal traveling at the speed of light to reach the spacecraft from Earth, and another 13 hours to receive an answer, so scientists began receiving the science data on Sunday.

However, the data gathered while the system was not working has been lost.

"During the last month, the spacecraft was transmitting engineering data, but there is no capability for on-board storage of the 160 bps cruise science data," Stone said.

Stone said that the scientists would not know whether there was a transient event even when they analyzed the Voyager 2 data, but they would be able to see if there was a significant change compared with before the data outage.

"However, there has been little solar activity over the last several years, so it is unlikely there were any significant transients," he added.

The Voyager 2 spacecraft is a twin of Voyager 1. It has been operating through the Solar System since August 20, 1977.

First, Voyager 2 was exploring Jupiter and Saturn, later it flew to explore Uranus and Neptune and then it headed into interstellar space.

Carl Sagan - Video: Our Place in the Universe

NASA Announces 2010 Carl Sagan Fellows

NASA Announces 2010 Carl Sagan Fellows

NASA has selected seven scientists as recipients of Carl Sagan Postdoctoral Fellowships in exoplanet exploration for 2010. The Sagan Fellowships support outstanding recent postdoctoral scientists in conducting independent research broadly related to the science goals of NASA's Exoplanet Exploration Program. That program's primary goal is to discover and characterize planetary systems and Earth-like planets around other stars.

"The Sagan Fellowship identifies and supports the most promising young scholars who are passionate about the scientific search for and study of planets beyond our solar system," said Charles Beichman, executive director of the NASA Exoplanet Science Institute at the California Institute of Technology in Pasadena. "These young scientists combine interest in the fields of astronomy, astrobiology or geophysics with expertise in theory, observation, or state-of-the-art instrumentation. They are following a trail blazed by Carl Sagan -- after whom the fellowship program is named -- that may one day lead to the discovery of life on worlds other than Earth."

The program, created in 2008, awards selected postdoctoral scientists with stipends of approximately $62,500 for up to three years, plus an annual research budget of $16,000. Topics range from techniques for detecting the glow of a dim planet in the blinding glare of its host star, to searching for the crucial ingredients of life in other planetary systems.

In addition to the Sagan Fellowships, NASA has two other astrophysics theme-based fellowship programs: the Einstein Fellowship Program, which supports research into the physics of the cosmos; and the Hubble Fellowship Program, which supports research into cosmic origins.

Read the full article here....

Carl Sagan's Voyager is 20 Years old

Image credit: NASA/JPL.

These six narrow-angle color images were made from the first ever 'portrait' of the solar system taken by Voyager 1, which was more than 4 billion miles from Earth and about 32 degrees above the ecliptic.

Twenty years ago on February 14, NASA's Voyager 1 spacecraft had sailed beyond the outermost planet in our solar system and turned its camera inward to snap a series of final images that would be its parting valentine to the string of planets it called home.

Mercury was too close to the sun to see, Mars showed only a thin crescent of sunlight, and Pluto was too dim, but Voyager was able to capture cameos of Neptune, Uranus, Saturn, Jupiter, Earth and Venus from its unique vantage point.

These images, later arranged in a large-scale mosaic, make up the only family portrait of our planets arrayed about the sun.

The Apollo missions in the 1960s and 70s had already altered our perspective of Earth by returning images of our home planet from the moon, but Voyager was providing a completely new perspective, said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena.

"It captured the Earth as a speck of light in the vastness of the solar system, which is our local neighborhood in the Milky Way galaxy, in a universe replete with galaxies," Stone said.

In the years since the twin Voyager spacecraft were launched in 1977, they had already sent back breathtaking, groundbreaking pictures of the gas giants Jupiter, Saturn, Uranus and Neptune. It took Voyager 1 more than 12 years to reach the place where it took the group portrait, 6 billion kilometers (almost 4 billion miles) away from the sun.

The imaging team started snapping images of the outer planets first because they were worried that pointing the camera near the sun would blind it and prevent more picture-taking.

Candy Hansen, a planetary scientist based at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who worked with the Voyager imaging team at the time, remembers combing through the images and finally finding the image of Earth. She had seen so many pictures over the years that she could distinguish dust on the lens from the black dots imprinted on the lens for geometric correction.

There was our planet, a bright speck sitting in a kind of spotlight of sunlight scattered by the camera. Hansen still gets chills thinking about it.

"I was struck by how special Earth was, as I saw it shining in a ray of sunlight," she said. "It also made me think about how vulnerable our tiny planet is."

This was the image that inspired Carl Sagan, the the Voyager imaging team member who had suggested taking this portrait, to call our home planet "a pale blue dot."

As he wrote in a book by that name, "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."

Carl Sagan speaks

Carl Sagan used to say, "extraordinary claims require extraordinary evidence"

Immortal Carl Sagan and the Pale Blue Dot - Our Earth

Carl Sagan - The late great Pulitzer Prize-winning author, who died in 1996, would have turned 75 on Monday 9 November 2009. Broward College is to hold a day of activities and talks in his memory.

The university, near Davie, Florida, held planetarium shows and star-gazing, as well as a talk by the magician and sceptic James Randi, a friend of Dr Sagan.

Dr Sagan, a professor of astronomy and space science at Cornell University and an adviser to Nasa, played a major role in setting up Seti, the Search for Extra-Terrestrial Intelligence.

However, he is probably best known to the public for the television series Cosmos: A Personal Voyage, and his books Pale Blue Dot and The Demon-Haunted World: Science as a Candle in the Dark.

As well as his research, he was a major science advocate and populariser, and a vociferous supporter of scepticism and rationality.

Robin Ince, the comedian and sceptic who organised the Nine Lessons and Carols for Godless People, an atheist celebration of Christmas, told the Telegraph: "Anyone who declares that science is dull or dry or boring only needs to read a paragraph of one of [Sagan’s] books or see a snippet of him talking to realise that they are utterly wrong.

"There should be more days like this, celebrating science and scientists. I know Newtonmas may not take over from Christmas, but perhaps Einstun could take over from Whitsun."

Phil Plait, the author of the Bad Astronomy blog and another speaker at Carl Sagan Day, said: “Sagan inspired a generation of astronomers, and in reality a whole generation of people, to look at the sky and appreciate the - yes, I’ll say it - cosmos.”