Voyager 1 Explores Final Frontier of Our ‘Solar Bubble’

Transitional Regions at the Heliosphere's Outer Limits (

Transitional Regions at the Heliosphere’s Outer Limits (

Data from Voyager 1, now more than 11 billion miles (18 billion kilometers) from the sun, suggest the spacecraft is closer to becoming the first human-made object to reach interstellar space.

Research using Voyager 1 data and published in the journal Science today provides new detail on the last region the spacecraft will cross before it leaves the heliosphere, or the bubble around our sun, and enters interstellar space. Three papers describe how Voyager 1’s entry into a region called the magnetic highway resulted in simultaneous observations of the highest rate so far of charged particles from outside heliosphere and the disappearance of charged particles from inside the heliosphere.

Scientists have seen two of the three signs of interstellar arrival they expected to see: charged particles disappearing as they zoom out along the solar magnetic field, and cosmic rays from far outside zooming in. Scientists have not yet seen the third sign, an abrupt change in the direction of the magnetic field, which would indicate the presence of the interstellar magnetic field.

“This strange, last region before interstellar space is coming into focus, thanks to Voyager 1, humankind’s most distant scout,” said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. “If you looked at the cosmic ray and energetic particle data in isolation, you might think Voyager had reached interstellar space, but the team feels Voyager 1 has not yet gotten there because we are still within the domain of the sun’s magnetic field.”

Scientists do not know exactly how far Voyager 1 has to go to reach interstellar space. They estimate it could take several more months, or even years, to get there. The heliosphere extends at least 8 billion miles (13 billion kilometers) beyond all the planets in our solar system. It is dominated by the sun’s magnetic field and an ionized wind expanding outward from the sun. Outside the heliosphere, interstellar space is filled with matter from other stars and the magnetic field present in the nearby region of the Milky Way.

Voyager 1 and its twin spacecraft, Voyager 2, were launched in 1977. They toured Jupiter, Saturn, Uranus and Neptune before embarking on their interstellar mission in 1990. They now aim to leave the heliosphere. Measuring the size of the heliosphere is part of the Voyagers’ mission.

The Science papers focus on observations made from May to September 2012 by Voyager 1’s cosmic ray, low-energy charged particle and magnetometer instruments, with some additional charged particle data obtained through April of this year.

Voyager 2 is about 9 billion miles (15 billion kilometers) from the sun and still inside the heliosphere. Voyager 1 was about 11 billion miles (18 billion kilometers) from the sun Aug. 25 when it reached the magnetic highway, also known as the depletion region, and a connection to interstellar space. This region allows charged particles to travel into and out of the heliosphere along a smooth magnetic field line, instead of bouncing around in all directions as if trapped on local roads. For the first time in this region, scientists could detect low-energy cosmic rays that originate from dying stars.

“We saw a dramatic and rapid disappearance of the solar-originating particles. They decreased in intensity by more than 1,000 times, as if there was a huge vacuum pump at the entrance ramp onto the magnetic highway,” said Stamatios Krimigis, the low-energy charged particle instrument’s principal investigator at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “We have never witnessed such a decrease before, except when Voyager 1 exited the giant magnetosphere of Jupiter, some 34 years ago.”

Other charged particle behavior observed by Voyager 1 also indicates the spacecraft still is in a region of transition to the interstellar medium. While crossing into the new region, the charged particles originating from the heliosphere that decreased most quickly were those shooting straightest along solar magnetic field lines. Particles moving perpendicular to the magnetic field did not decrease as quickly. However, cosmic rays moving along the field lines in the magnetic highway region were somewhat more populous than those moving perpendicular to the field. In interstellar space, the direction of the moving charged particles is not expected to matter.

In the span of about 24 hours, the magnetic field originating from the sun also began piling up, like cars backed up on a freeway exit ramp. But scientists were able to quantify that the magnetic field barely changed direction — by no more than 2 degrees.

“A day made such a difference in this region with the magnetic field suddenly doubling and becoming extraordinarily smooth,” said Leonard Burlaga, the lead author of one of the papers, and based at NASA’s Goddard Space Flight Center in Greenbelt, Md. “But since there was no significant change in the magnetic field direction, we’re still observing the field lines originating at the sun.”

NASA Voyager Status Update on Voyager1 Location

Artist's concept of NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech

Artist’s concept of NASA’s Voyager spacecraft. Image credit: NASA/JPL-Caltech

“The Voyager team is aware of reports today that NASA’s Voyager 1 has left the solar system,” said Edward Stone, Voyager project scientist based at the California Institute of Technology, Pasadena, Calif. “It is the consensus of the Voyager science team that Voyager 1 has not yet left the solar system or reached interstellar space. In December 2012, the Voyager science team reported that Voyager 1 is within a new region called ‘the magnetic highway’ where energetic particles changed dramatically. A change in the direction of the magnetic field is the last critical indicator of reaching interstellar space and that change of direction has not yet been observed.”
To learn more about the current status of the Voyager mission, visit:

Read also: Recent Voyager 1 data indicate that on August 25, 2012 at a distance of 121.7 AU from the Sun, sudden and unprecedented intensity changes were observed in anomalous and galactic cosmic rays

Voyager 1: beyond the edge of the solar system at last?

Number of particles (mainly protons) from the sun hitting Voyager 1 against time. Notice the huge drop around September – that’s one of the pieces of evidence that Voyager 1 is now in interstellar space. Credit: NASA

By Kelly Oakes
It was on my first birthday that the Voyager 1 spacecraft turned around and took a picture of the pale blue dot we call home. That picture was Voyager’s last glimpse of Earth before its camera was switched off and it began to sail, uninterrupted, towards interstellar space. Around the same time Voyager 2 finished its tour of the outer planets and joined Voyager 1 on its interstellar mission.

So by the time I came to learn about the Voyager spacecraft they were both well on their way to the edge of the solar system. Now one of them might have finally left.

I wrote about Voyager for my entry into this year’s Wellcome Trust Science Writing Prize, in association with the Guardian and the Observer. My entry – Beyond the edge of the solar system – was shortlisted and is up on the Wellcome Trust blog today.

And just in time! It looks as if, after all that waiting, Voyager 1 has finally broken through to the other side. It’s not quite official yet, but a huge drop in the number charged particles hitting Voyager 1 indicated that it passed through some kind of boundary around the start of September. Data from its magnetometer will be needed to confirm what exactly has happened, but I will be keeping my eyes peeled for an announcement soon.

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Particles point way for Nasa’s Voyager

The domain of the Sun’s influence is called the heliosphere: The Voyagers are approaching the edge of this enormous balloon of charged particles thrown out into space by our star

Scientists working on Voyager 1 are receiving further data suggesting the probe is close to crossing into interstellar space.

The Nasa mission, which launched from Earth in 1977, could leave our Solar System at any time.

It is now detecting a sharp rise in the number of high-energy particles hitting it from distant exploded stars.

The observation was predicted, and is another indication that Voyager will soon reach its historic goal.

“The laws of physics say that someday Voyager will become the first human-made object to enter interstellar space, but we still do not know exactly when that someday will be,” Ed Stone, the Voyager project scientist at the California Institute of Technology in Pasadena, said in a Nasa statement.

“The latest data indicate that we are clearly in a new region where things are changing more quickly. It is very exciting. We are approaching the Solar System’s frontier.”

Voyager 1 is travelling at about 17 km per second (38,000 mph), and is almost 18 billion km (11 billion miles) from Earth.

The vast separation means a signal from the probe takes more than 16 and a half hours to arrive at Nasa’s receiving network.

In the last three years, Voyager has seen a steady increase in the number of cosmic rays entering its two high-energy telescopes, but in the past month the counts have jumped markedly…..
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Voyager instrument cooling after heater turned off

Artist's concept of NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech

In order to 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…
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NASA’s Voyager Hits New Region at Solar System Edge

In this artist's concept, NASA's Voyager 1 spacecraft has entered a new region between our solar system and interstellar space, which scientists are calling the stagnation region. Image credit: NASA/JPL-Caltech

PASADENA, Calif. — NASA’s Voyager 1 spacecraft has entered a new region between our solar system and interstellar space. Data obtained from Voyager over the last year reveal this new region to be a kind of cosmic purgatory. In it, the wind of charged particles streaming out from our sun has calmed, our solar system’s magnetic field has piled up, and higher-energy particles from inside our solar system appear to be leaking out into interstellar space.

“Voyager tells us now that we’re in a stagnation region in the outermost layer of the bubble around our solar system,” said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. “Voyager is showing that what is outside is pushing back. We shouldn’t have long to wait to find out what the space between stars is really like.”

Although Voyager 1 is about 11 billion miles (18 billion kilometers) from the sun, it is not yet in interstellar space. In the latest data, the direction of the magnetic field lines has not changed, indicating Voyager is still within the heliosphere, the bubble of charged particles the sun blows around itself. The data do not reveal exactly when Voyager 1 will make it past the edge of the solar atmosphere into interstellar space, but suggest it will be in a few months to a few years.

The latest findings, described today at the American Geophysical Union’s fall meeting in San Francisco, come from Voyager’s Low Energy Charged Particle instrument, Cosmic Ray Subsystem and Magnetometer.

Scientists previously reported the outward speed of the solar wind had diminished to zero in April 2010, marking the start of the new region. Mission managers rolled the spacecraft several times this spring and summer to help scientists discern whether the solar wind was blowing strongly in another direction. It was not. Voyager 1 is plying the celestial seas in a region similar to Earth’s doldrums, where there is very little wind.

During this past year, Voyager’s magnetometer also detected a doubling in the intensity of the magnetic field in the stagnation region. Like cars piling up at a clogged freeway off-ramp, the increased intensity of the magnetic field shows that inward pressure from interstellar space is compacting it.

Voyager has been measuring energetic particles that originate from inside and outside our solar system. Until mid-2010, the intensity of particles originating from inside our solar system had been holding steady. But during the past year, the intensity of these energetic particles has been declining, as though they are leaking out into interstellar space. The particles are now half as abundant as they were during the previous five years.

At the same time, Voyager has detected a 100-fold increase in the intensity of high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside, which is another indication of the approaching boundary.

“We’ve been using the flow of energetic charged particles at Voyager 1 as a kind of wind sock to estimate the solar wind velocity,” said Rob Decker, a Voyager Low-Energy Charged Particle Instrument co-investigator at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. “We’ve found that the wind speeds are low in this region and gust erratically. For the first time, the wind even blows back at us. We are evidently traveling in completely new territory. Scientists had suggested previously that there might be a stagnation layer, but we weren’t sure it existed until now.”

Launched in 1977, Voyager 1 and 2 are in good health. Voyager 2 is 9 billion miles (15 billion kilometers) away from the sun.

The Voyager spacecraft were built by NASA’s Jet Propulsion Laboratory in Pasadena, Calif., which continues to operate both. JPL is a division of the California Institute of Technology. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington. For more information about the Voyager spacecraft, visit:  –

Voyager at the edge

The Voyager 1 spacecraft, and its partner, Voyager 2, are approaching the edge of the Sun's protective bubble.

Spacecraft finds unexpected calm at the boundary of Sun’s bubble.
Seventeen and a half billion kilometres from Earth, mankind’s most distant probe seems to be on the edge of interstellar space.
The Voyager 1 spacecraft is at the limit of the ‘heliosheath’, where particles streaming from the Sun clash with the gases of the galaxy. Contrary to scientists’ expectation of a sharp, violent edge, the boundary seems to be a tepid place, where the solar wind mingles with extrasolar particles.
“We’re in this mixed-up region where the Sun still has some influence,” says Stamatios Krimigis, a physicist at the Applied Physics Laboratory of Johns Hopkins University in Laurel, Maryland. “It’s certainly not what we thought.”
The new findings, reported by Krimigis and his colleagues this week in Nature, are the latest of many during the spacecraft’s long journey1. Launched in 1977, Voyager 1 photographed active volcanoes on the moon Io on its way past Jupiter in 1979. The following year, it confirmed the existence of three new moons orbiting Saturn. In one of its final photographs, transmitted in 1990, Earth appears as a grainy speck bathed in the rainbow rays of the Sun.

Crossing the unknown

Since then, NASA scientists have shut down six of its ten instruments, and it is so far away that transmissions now take more than 16 hours to reach Earth. But Voyager’s work continues. It is now travelling out of the heliosphere, the bubble of space filled by the Sun’s wind. In late 2004, Voyager 1 crossed the ‘termination shock’, the boundary beyond which the solar wind’s influence begins to wane. And this year researchers were expecting it to meet another boundary — one at which the solar wind sharply reverses direction, signalling the beginning of interstellar space.
Instead, Krimigis says, measurements of low-energy charged particles show that the solar wind has gradually slowed to zero and is mingling with interstellar gases. Theories failed to predict this mixed-up environment, and Krimigis says it may even be possible that this is, in fact, what interstellar space looks like. “We may have crossed and don’t know it, because nobody has a model that describes what we’re seeing,” he says.
The blowing of far-flung interstellar gases may seem inconsequential to those of us closer to the Sun, but the details do matter, says Voyager’s chief scientist Ed Stone at the California Institute of Technology in Pasadena. The Sun is currently flying through debris from several nearby supernovae. Streams of particles and the magnetic fields produced by our star are shielding us from the some of the interstellar radiation from the blasts, he says. “The size of this bubble is important.”
Voyager should be able to provide more answers in the coming years. The spacecraft’s plutonium power plant will allow it to operate smoothly until at least 2020, and “we will continue to be taking data”, says Krimigis. Even after its signal fades, the spacecraft’s journey will continue; it should pass the constellation Camelopardalis in around 40,000 years.


1. Stamatios M. Krimigis, Edmond C. Roelof, Robert B. Decker & Matthew E. Hill
Voyager 1 has been in the reservoir of energetic ions and electrons that constitutes the heliosheath since it crossed the solar wind termination shock on 16 December 2004 at a distance from the Sun of 94 astronomical units (1 AU = 1.5 × 108 km). It is now ~22 AU past the termination shock crossing. The bulk velocity of the plasma in the radial–transverse plane has been determined using measurements of the anisotropy of the convected energetic ion distribution. Here we report that the radial component of the velocity has been decreasing almost linearly over the past three years, from ~70 km s−1 to ~0 km s−1, where it has remained for the past eight months. It now seems that Voyager 1 has entered a finite transition layer of zero-radial-velocity plasma flow, indicating that the spacecraft may be close to the heliopause, the border between the heliosheath and the interstellar plasma. The existence of a flow transition layer in the heliosheath contradicts current predictions—generally assumed by conceptual models—of a sharp discontinuity at the heliopause……