Tag Archives: Voyager

Pale Blue 2Dot0


Thanks to the prodding of Carl Sagan, just over 25 years ago, on February 14, 1990 to be exact, the Voyager 1 spacecraft turned its camera towards Earth and snapped what has since become an iconic image. It showed our home planet as a very small, very pale blue dot — much as you’d expect from a distance of around 3.7 billion miles.

Though much closer to Earth, the Cassini spacecraft snapped a similar shot of our planet in 2013. Cassini is in its seemingly never-ending orbits of discovery around the Saturnian system, which it began over 10 years ago. It took the image in 2013: Earth in the distance at the center right is dwarfed by Saturn’s rings in the foreground. A rare, beautiful and remarkable image!

Image: Saturn’s rings and Earth in the same frame. Taken on July 19, 2013, via the wide-angle camera on NASA’s Cassini spacecraft Courtesy: NASA/JPL-Caltech/Space Science Institute.

Above and Beyond

According to NASA, Voyager 1 officially left the protection of the solar system on or about August 25, 2013, and is now heading into interstellar space. It is now the first and only human-made object to leave the solar system.

Perhaps, one day in the distant future real human voyagers — or their android cousins — will come across the little probe as it continues on its lonely journey.

From Space:

A spacecraft from Earth has left its cosmic backyard and taken its first steps in interstellar space.

After streaking through space for nearly 35 years, NASA’s robotic Voyager 1 probe finally left the solar system in August 2012, a study published today (Sept. 12) in the journal Science reports.

“Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, and as it enters interstellar space, it adds a new chapter in human scientific dreams and endeavors,” NASA science chief John Grunsfeld said in a statement. “Perhaps some future deep-space explorers will catch up with Voyager, our first interstellar envoy, and reflect on how this intrepid spacecraft helped enable their future.”

A long and historic journey

Voyager 1 launched on Sept. 5, 1977, about two weeks after its twin, Voyager 2. Together, the two probes conducted a historic “grand tour” of the outer planets, giving scientists some of their first up-close looks at Jupiter, Saturn, Uranus, Neptune and the moons of these faraway worlds.

The duo completed its primary mission in 1989, and then kept on flying toward the edge of the heliosphere, the huge bubble of charged particles and magnetic fields that the sun puffs out around itself. Voyager 1 has now popped free of this bubble into the exotic and unexplored realm of interstellar space, scientists say.

They reached this historic conclusion with a little help from the sun. A powerful solar eruption caused electrons in Voyager 1’s location to vibrate signficantly between April 9 and May 22 of this year. The probe’s plasma wave instrument detected these oscillations, and researchers used the measurements to figure out that Voyager 1’s surroundings contained about 1.3 electrons per cubic inch (0.08 electrons per cubic centimeter).

That’s far higher than the density observed in the outer regions of the heliosphere (roughly 0.03 electrons per cubic inch, or 0.002 electrons per cubic cm) and very much in line with the 1.6 electrons per cubic inch (0.10 electrons per cubic cm) or so expected in interstellar space. [Photos from NASA’s Voyager 1 and 2 Probes]

“We literally jumped out of our seats when we saw these oscillations in our data — they showed us that the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble,” study lead author Don Gurnett of the University of Iowa, the principal investigator of Voyager 1’s plasma wave instrument, said in a statement.

It may seem surprising that electron density is higher beyond the solar system than in its extreme outer reaches. Interstellar space is, indeed, emptier than the regions in Earth’s neighborhood, but the density inside the solar bubble drops off dramatically at great distances from the sun, researchers said.

Calculating a departure date

The study team wanted to know if Voyager 1 left the solar system sometime before April 2013, so they combed through some of the probe’s older data. They found a monthlong period of electron oscillations in October-November 2012 that translated to a density of 0.004 electrons per cubic inch (0.006 electrons per cubic cm).

Using these numbers and the amount of ground that Voyager 1 covers — about 325 million miles (520 million kilometers) per year — the researchers calculated that the spacecraft likely left the solar system in August 2012.

That time frame matches up well with several other important changes Voyager 1 observed. On Aug. 25, 2012, the probe recorded a 1,000-fold drop in the number of charged solar particles while also measuring a 9 percent increase in fast-moving galactic cosmic rays, which originate beyond the solar system.

“These results, and comparison with previous heliospheric radio measurements, strongly support the view that Voyager 1 crossed the heliopause into the interstellar plasma on or about Aug. 25, 2012,” Gurnett and his colleagues write in the new study.

At that point, Voyager 1 was about 11.25 billion miles (18.11 billion km) from the sun, or roughly 121 times the distance between Earth and the sun. The probe is now 11.66 billion miles (18.76 billion km) from the sun. (Voyager 2, which took a different route through the solar system, is currently 9.54 billion miles, or 15.35 billion km, from the sun.)

Read the entire article here.

Image: Voyager Gold Disk. Courtesy of Wikipedia.

Voyager: A Gift that Keeps on Giving

The little space probe that could — Voyager I — is close to leaving our solar system and entering the relative void of interstellar space. As it does so, from a distance of around 18.4 billion kilometers (today), it continues to send back signals of what it finds. And, surprises continue.

[div class=attrib]From ars technica:[end-div]

Several years ago the Voyager spacecraft neared the edge of the Solar System, where the solar wind and magnetic field started to be influenced by the pressure from the interstellar medium that surrounds them. But the expected breakthrough to interstellar space appeared to be indefinitely put on hold; instead, the particles and magnetic field lines in the area seemed to be sending mixed signals about the Voyagers’ escape. At today’s meeting of the American Geophysical Union, scientists offered an explanation: the durable spacecraft ran into a region that nobody predicted.

The Voyager probes were sent on a grand tour of the outer planets over 35 years ago. After a series of staggeringly successful visits to the planets, the probes shot out beyond the most distant of them toward the edges of the Solar System. Scientists expected that as they neared the edge, we’d see the charge particles of the solar wind changing direction as the interstellar medium alters the direction of the Sun’s magnetic field. But while some aspects of the Voyager’s environment have changed, we’ve not seen any clear indication that it has left the Solar System. The solar wind actually seems to be grinding to a halt.

Today’s announcement clarifies that the confusion was caused by the fact that nature didn’t think much of physicists’ expectations. Instead, there’s an additional region near our Solar System’s boundary that hadn’t been predicted.

Within the Solar System, the environment is dominated by the solar magnetic field and a flow of charged particles sent out by the Sun (called the solar wind). Interstellar space has its own flow of particles in the form of low-energy cosmic rays, which the Sun’s magnetic field deflects away from us. There’s also an interstellar magnetic field with field lines oriented in different directions to our Sun’s.

Researchers expected the Voyagers would reach a relatively clear boundary between the Solar System and interstellar space. The Sun’s magnetic field would first shift directions, then be left behind and the interstellar one would be detected. At the same time, we’d see the loss of the solar wind and start seeing the first low-energy cosmic rays.

As expected, a few years back, the Voyagers reached a region where the interstellar medium forced the Sun’s magnetic field lines to curve north. But the solar wind refused to follow suit. Instead of flowing north, the solar wind slowed to a halt while the cosmic rays were missing in action.

Over the summer, as Voyager 1 approached 122 astronomical units from the Sun, that started to change. Arik Posner of the Voyager team said that, starting in late July, Voyager 1 detected a sudden drop in the presence of particles from the solar wind, which went down by half. At the same time, the first low-energy cosmic rays filtered in. A few days later things returned to normal. A second drop occurred on August 15 and then, on August 28, things underwent a permanent shift. According to Tom Krimigis, particles originating from the Sun dropped by about 1,000-fold. Low-energy cosmic rays rose and stayed elevated.

[div class=attrib]Read the entire article following the jump.[end-div]

[div class=attrib]Image: Voyager II. Courtesy of NASA / JPL.[end-div]

One Pale Blue Dot, 55 Languages and 11 Billion Miles

It was Carl Sagan’s birthday last week (November 9, to be precise). He would have been 77 years old — he returned to “star-stuff” in 1996. Thoughts of this charming astronomer and cosmologist reminded us of a project with which he was intimately involved — the Voyager program.

In 1977, NASA launched two spacecraft to explore Jupiter and Saturn. The spacecraft performed so well that their missions were extended several times: first, to journey farther in the outer reaches of our solar system and explore the planets Neptune and Uranus; and second, to fly beyond our solar system into interstellar space. And, by all accounts both craft are now close to this boundary. The farthest, Voyager I, is currently over 11 billion miles away. For a real-time check on its distance, visit  JPL’s Voyager site here. JPL is NASA’s Jet Propulsion Lab in Pasadena, CA.

Some may recall that Carl Sagan presided over the selection and installation of content from the Earth onto a gold plated disk that each Voyager carries on its continuing mission. The disk contains symbolic explanations of our planet and solar system, as well as images of its inhabitants and greetings spoken in 55 languages. After much wrangling over concerns about damaging Voyager’s imaging instruments by peering back at the Sun, Sagan was instrumental in having NASA reorient Voyager I’s camera back towards the Earth. This enabled the craft to snap one last set of images of our planet from its vantage point in deep space. One poignant image became know as the “Pale Blue Dot”, and Sagan penned some characteristically eloquent and philosophical words about this image in his book, Pale Blue Dot: A Vision of the Human Future in Space.

[div class=attrib]From Carl Sagan:[end-div]

From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Look again at that dot. 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. The aggregate of our joy and suffering, thousands of confident religions, ideologies and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every “superstar,” every “supreme leader,” every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.

[div class=attrib]About the image from NASA:[end-div]

From Voyager’s great distance Earth is a mere point 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. This blown-up image of the Earth was taken through three color filters – violet, blue and green – and recombined to produce the color image. The background features in the image are artifacts resulting from the magnification.

To ease identification we have drawn a gray circle around the image of the Earth.

[div class=attrib]Image courtesy of NASA / JPL.[end-div]