Voyager 1: Is It In or Is It Out?

Nearly 18.7 billion kilometers from Earth — about 17 light-hours away — NASA’s Voyager 1 spacecraft is just about on the verge of entering interstellar space, a wild and unexplored territory of high-energy cosmic particles into which no human-made object has ever ventured. Launched in September 1977, Voyager 1 will soon become the first spacecraft to officially leave the Solar System.

Or has it already left?

I won’t pretend I haven’t heard it before: Voyager 1 has left the Solar System! Usually followed soon after by: um, no it hasn’t. And while it might all seem like an awful lot of flip-flopping by supposedly-respectable scientists, the reality is there’s not a clear boundary that defines the outer limits of our Solar System. It’s not as simple as Voyager rolling over a certain mileage, cruising past a planetary orbit, or breaking through some kind of discernible forcefield with a satisfying “pop.” (Although that would be cool.)

The outer edge of the heliosphere has been found to contain many different regions, which Voyager 1 has been passing through since 2004. (NASA/JPL-Caltech)
The outer edge of the heliosphere has been found to contain many different regions, which Voyager 1 has been passing through since 2004. (NASA/JPL-Caltech)

Rather, scientists look at Voyager’s data for evidence of a shift in the type of particles detected. Within the transitionary zone that the spacecraft has most recently been traveling through, low-energy particles from the Sun are outnumbered by higher-energy particles zipping through interstellar space, also called the local interstellar medium (LISM). Voyager’s instruments have been detecting dramatic shifts in the concentrations of each for over a year now, unmistakably trending toward the high-energy end — or at least showing a severe drop-off in solar particles — and researchers from the University of Maryland are claiming that this, along with their model of a porous solar magnetic field, indicates Voyager has broken on through to the other side.

Read more: Voyagers Find Giant Jacuzzi-like Bubbles at Edge of Solar System

“It’s a somewhat controversial view, but we think Voyager has finally left the Solar System, and is truly beginning its travels through the Milky Way,” said Marc Swisdak, UMD research scientist and lead author of a new paper published this week in The Astrophysical Journal Letters.

According to Swisdak, fellow UMD plasma physicist James F. Drake, and Merav Opher of Boston University, their model of the outer edge of the Solar System  fits recent Voyager 1 observations — both expected and unexpected. In fact, the UMD-led team says that Voyager passed the outer boundary of the Sun’s magnetic influence, aka the heliopause… last year.

Read more: Winds of Change at the Edge of the Solar System

But, like some of last year’s claims, these conclusions aren’t shared by mission scientists at NASA.

“Details of a new model have just been published that lead the scientists who created the model to argue that NASA’s Voyager 1 spacecraft data can be consistent with entering interstellar space in 2012,” said Ed Stone, Voyager project scientist at Caltech, in a press release issued today. “In describing on a fine scale how magnetic field lines from the sun and magnetic field lines from interstellar space can connect to each other, they conclude Voyager 1 has been detecting the interstellar magnetic field since July 27, 2012. Their model would mean that the interstellar magnetic field direction is the same as that which originates from our sun.

The famous "Golden Record" carried aboard both Voyager 1 and 2 contains images, sounds and greetings from Earth. (NASA)
The famous “Golden Record” carried aboard both Voyager 1 and 2 contains images, sounds and greetings from Earth. (NASA)

“Other models envision the interstellar magnetic field draped around our solar bubble and predict that the direction of the interstellar magnetic field is different from the solar magnetic field inside. By that interpretation, Voyager 1 would still be inside our solar bubble.”

Stone says that further discussion and investigation will be needed to “reconcile what may be happening on a fine scale with what happens on a larger scale.”

Whether still within the Solar System — however it’s defined — or outside of it, the bottom line is that the venerable Voyager spacecraft are still conducting groundbreaking research of our cosmic neighborhood, 36 years after their respective launches and long after their last views of the planets. And that’s something nobody can argue about.

“The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before. We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier.”

– Ed Stone, Voyager project scientist

Built by JPL and launched in 1977, both Voyagers are still capable of returning scientific data from a full range of instruments, with adequate power and propellant to remain operating until 2020.

Read the full UMD news release here, and find out more about the Voyager mission on the NASA/JPL website here.


Note: The definition of “Solar System” used in this article is in reference to the Sun’s magnetic influence, the heliosphere, and all that falls within its outermost boundary, the heliopause (wherever that is.) Objects farther out are still gravitationally held by the Sun, such as distant KBOs and Oort Cloud comets, but orbit within the interstellar medium. 

U.S. To Restart Plutonium Production for Deep Space Exploration

The end of NASA’s plutonium shortage may be in sight. On Monday March 18th,  NASA’s planetary science division head Jim Green announced that production of Plutonium-238 (Pu-238) by the United States Department of Energy (DOE) is currently in the test phases leading up to a restart of full scale production.

“By the end of the calendar year, we’ll have a complete plan from the Department of Energy on how they’ll be able to satisfy our requirement of 1.5 to 2 kilograms a year.” Green said at the 44th Lunar and Planetary Science Conference being held in Woodlands, Texas this past Monday.

This news comes none too soon. We’ve written previously on the impending Plutonium shortage and the consequences it has for future deep space exploration. Solar power is adequate in most cases when you explore the inner solar system, but when you venture out beyond the asteroid belt, you need nuclear power to do it.

Production of the isotope Pu-238 was a fortunate consequence of the Cold War.  First produced by Glen Seaborg in 1940, the weapons grade isotope of plutonium (-239) is produced via bombarding neptunium (which itself is a decay product of uranium-238) with neutrons. Use the same target isotope of Neptunium-237 in a fast reactor, and Pu-238 is the result. Pu-238 produces 280x times the decay heat at 560 watts per kilogram versus weapons grade Pu-239  and is ideal as a compact source of energy for deep space exploration.

Since 1961, over 26 U.S. spacecraft have been launched carrying Multi-Mission Radioisotope Thermoelectric Generators (MMRTG, or formerly simply RTGs) as power sources and have explored every planet except Mercury. RTGs were used by the Apollo Lunar Surface Experiments Package (ALSEP) science payloads left on by the astronauts on the Moon, and Cassini, Mars Curiosity and New Horizons enroute to explore Pluto in July 2015 are all nuclear powered.

Plutonium powered RTGs are the only technology that we have currently in use that can carry out deep space exploration. NASA’s Juno spacecraft will be the first to reach Jupiter in 2016 without the use of a nuclear-powered RTG, but it will need to employ 3 enormous 2.7 x 8.9 metre solar panels to do it.

The plutonium power source inside the Mars Science Laboratory's MMRTG during assembly at the Idaho National Laboratory. (Credit: Department of Energy?National Laboratory image under a Creative Commons Generic Attribution 2.0 License).
The plutonium power source inside the Mars Science Laboratory’s MMRTG during assembly at the Idaho National Laboratory. (Credit: Department of Energy/Idaho National Laboratory image under a Creative Commons Generic Attribution 2.0 License).

The problem is, plutonium production in the U.S. ceased in 1988 with the end of the Cold War. How much Plutonium-238 NASA and the DOE has stockpiled is classified, but it has been speculated that it has at most enough for one more large Flag Ship class mission and perhaps a small Scout class mission. Plus, once weapons grade plutonium-239 is manufactured, there’s no re-processing it the desired Pu-238 isotope. The plutonium that currently powers Curiosity across the surface of Mars was bought from the Russians, and that source ended in 2010. New Horizons is equipped with a spare MMRTG that was built for Cassini, which was launched in 1999.

Technicians handle an RTG at the Payload Hazardous Servicing Facility at the Kennedy Space Center for the Cassini spacecraft. (Credit: NASA).
Technicians handle an RTG at the Payload Hazardous Servicing Facility at the Kennedy Space Center for the Cassini spacecraft. (Credit: NASA).

As an added bonus, plutonium powered missions often exceed expectations as well. For example, the Voyager 1 & 2 spacecraft had an original mission duration of five years and are now expected to continue well into their fifth decade of operation. Mars Curiosity doesn’t suffer from the issues of “dusty solar panels” that plagued Spirit and Opportunity and can operate through the long Martian winter. Incidentally, while the Spirit and Opportunity rovers were not nuclear powered, they did employ tiny pellets of plutonium oxide in their joints to stay warm, as well as radioactive curium to provide neutron sources in their spectrometers. It’s even quite possible that any alien intelligence stumbles upon the five spacecraft escaping our solar system (Pioneer 10 & 11, Voyagers 1 & 2, and New Horizons) could conceivably date their departure from Earth by measuring the decay of their plutonium power source. (Pu-238 has a half life of 87.7 years and eventually decays after transitioning through a long series of daughter isotopes into lead-206).

New Horizons in the Payload Hazardous Servicing Facility at the Kennedy Space Center. Note the RTG (black) protruding from the spacecraft. (Credit: NASA/Uwe W.)
New Horizons in the Payload Hazardous Servicing Facility at the Kennedy Space Center. Note the RTG (black) protruding from the spacecraft. (Credit: NASA/Uwe W.)

The current production run of Pu-238 will be carried out at the Oak Ridge National Laboratory (ORNL) using its High Flux Isotope Reactor (HFIR). “Old” Pu-238 can also be revived by adding newly manufactured Pu-238 to it.

“For every 1 kilogram, we really revive two kilograms of the older plutonium by mixing it… it’s a critical part of our process to be able to utilize our existing supply at the energy density we want it,” Green told a recent Mars exploration planning committee.

Still, full target production of 1.5 kilograms per year may be some time off. For context, the Mars rover Curiosity utilizes 4.8 kilograms of Pu-238, and New Horizons contains 11 kilograms. No missions to the outer planets have left Earth since the launch of Curiosity in November 2011, and the next mission likely to sport an RTG is the proposed Mars 2020 rover. Ideas on the drawing board such as a Titan lake lander and a Jupiter Icy Moons mission would all be nuclear powered.

Engineers perform a fit check of the MMRTG on Curiousity at the Kennedy Space Center. The final installation of the MMRTG occured the evening prior to launch. (Credit: NASA/Cory Huston).
Engineers perform a fit check of the MMRTG on Curiosity at the Kennedy Space Center. The final installation of the MMRTG occurred the evening prior to launch. (Credit: NASA/Cory Huston).

Along with new plutonium production, NASA plans to have two new RTGs dubbed Advanced Stirling Radioisotope Generators (ASRGs) available by 2016. While more efficient, the ASRG may not always be the device of choice. For example, Curiosity uses its MMRTG waste heat to keep instruments warm via Freon circulation.  Curiosity also had to vent waste heat produced by the 110-watt generator while cooped up in its aero shell enroute to Mars.

Cutaway diagram of the Advanced Stirling Radioisotope Generator. (Credit: DOE/NASA).
Cutaway diagram of the Advanced Stirling Radioisotope Generator. (Credit: DOE/NASA).

And of course, there are the added precautions that come with launching a nuclear payload. The President of the United States had to sign off on the launch of Curiosity from the Florida Space Coast. The launch of Cassini, New Horizons, and Curiosity all drew a scattering of protesters, as does anything nuclear related. Never mind that coal fired power plants produce radioactive polonium, radon and thorium as an undesired by-product daily.

An RTG (in the foreground on the pallet) left on the Moon by astronauts during Apollo 14.  (Credit: NASA/Alan Shepard).
An RTG (in the foreground on the pallet) left on the Moon by astronauts during Apollo 14. (Credit: NASA/Alan Shepard).

Said launches aren’t without hazards, albeit with risks that can be mitigated and managed. One of the most notorious space-related nuclear accidents occurred early in the U.S. space program with the loss of an RTG-equipped Transit-5BN-3 satellite off of the coast of Madagascar shortly after launch in 1964. And when Apollo 13 had to abort and return to Earth, the astronauts were directed to ditch the Aquarius Landing Module along with its nuclear-powered science experiments meant for the surface of the Moon in the Pacific Ocean near the island of Fiji. (They don’t tell you that in the movie) One wonders if it would be cost effective to “resurrect” this RTG from the ocean floor for a future space mission. On previous nuclear-equipped launches such as New Horizons, NASA placed the chance of a “launch accident that could release plutonium” at 350-to-1 against  Even then, the shielded RTG is “over-engineered” to survive an explosion and impact with the water.

But the risks are worth the gain in terms of new solar system discoveries. In a brave new future of space exploration, the restart of plutonium production for peaceful purposes gives us hope. To paraphrase Carl Sagan, space travel is one of the best uses of nuclear fission that we can think of!

A Valentine From Voyager

On February 14, 1990, after nearly 13 years of travel through the outer Solar System, NASA’s Voyager 1 spacecraft crossed the orbit of Pluto and turned its camera around, capturing photos of the planets as seen from that vast distance. It was a family portrait taken from over 4.4 billion kilometers away — the ultimate space Valentine.

Who says astronomy isn’t romantic?

Full mosaic of Voyager 1 images taken on Feb. 14, 1990 (NASA/JPL)
Full mosaic of Voyager 1 images taken on Feb. 14, 1990 (NASA/JPL)

“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

VoyagerValentineIt was the unique perspective above provided by Voyager 1 that inspired Carl Sagan to first coin the phrase “Pale Blue Dot” in reference to our planet. And it’s true… from the edges of the solar system Earth is just a pale blue dot in a black sky, a bright speck just like all the other planets. It’s a sobering and somewhat chilling image of our world… but also inspiring, as the Voyager 1 and 2 spacecraft are now the farthest human-made objects in existence — and getting farther every second. They still faithfully transmit data back to us even now, over 35 years since their launches, from 18.5 and 15.2 billion kilometers away.

The Voyagers sure know the value of a long-term relationship.

See more news from the Voyager mission here.

We Are Made of Stardust

This brief quote by the late Carl Sagan is wonderfully illustrated in the beautiful and poignant short film “Stardust,” directed by Mischa Rozema of Amsterdam-based media company PostPanic. Using actual images from space exploration as well as CGI modeling, Stardust reminds us that everything we and the world around us are made of was created inside stars… and that, one day, our home star will once again free all that “stuff” back out into the Universe.

The film was made in memory of talented Dutch designer Arjan Groot, who died of cancer in July 2011 at the age of 39.

“I wanted to show the universe as a beautiful but also destructive place. It’s somewhere we all have to find our place within. As a director, making Stardust was a very personal experience but it’s not intended to be a personal film and I would want people to attach their own meanings to the film so that they can also find comfort based on their own histories and lives.”
– Mischa Rozema, director

A truly stunning tribute.

See more about this on PostPanic’s Vimeo page. (Credits after the jump.)

A PostPanic Production
Written & directed by Mischa Rozema
Produced by Jules Tervoort
VFX Supervisor: Ivor Goldberg
Associate VFX Supervisor: Chris Staves
Senior digital artists: Matthijs Joor, Jeroen Aerts
Digital artists: Marti Pujol, Silke Finger, Mariusz Kolodziejczak, Dieuwer Feldbrugge, Cara To, Jurriën Boogert
Camera & edit: Mischa Rozema
Production: Ania Markham, Annejes van Liempd
Audio by Pivot Audio , Guy Amitai
Featuring “Helio” by Ruben Samama
Copyright 2013 Post Panic BV, All rights reserved

In the grand scheme of the universe, nothing is ever wasted and it finds comfort in us all essentially being Stardust ourselves. Voyager represents the memories of our loved ones and lives that will never disappear.

27 Years Ago: Voyager 2’s Visit to Uranus

Image of Uranus’ crescent taken by a departing Voyager 2 on January 25, 1986 (NASA/JPL)

27 years ago today, January 24, 1986, NASA’s Voyager 2 spacecraft sped past Uranus, becoming simultaneously the first and last spacecraft to visit the blue-tinged gas giant, third largest planet in the Solar System.

The image above shows the crescent-lit Uranus as seen by Voyager 2 from a distance of about 965,000 km (600,000 miles.) At the time the spacecraft had already passed Uranus and was looking back at the planet on its way outwards toward Neptune.

Although composed primarily of hydrogen and helium, trace amounts of methane in Uranus’ uppermost atmosphere absorb most of the red wavelengths of light, making the planet appear a pale blue color.


Image of the 1,500-km-wide Oberon acquired by Voyager 2 on Jan. 24, 1986 (NASA/JPL)

The second of NASA’s twin space explorers (although it launched first) Voyager 2 came within 81,800 kilometers (50,600 miles) of Uranus on January 24, 1986, gathering images of the sideways planet, its rings and several of its moons. Voyager 2 also discovered the presence of a magnetic field around Uranus, as well as 10 new small moons.


Three moons discovered by Voyager 2 in 1986 (NASA/JPL)

Data gathered by Voyager 2 revealed that Uranus’ rate of rotation is 17 hours, 14 minutes.

At the time of this writing, Voyager 2 is 15,184,370,900 km from Earth and steadily moving toward the edge of the Solar System at a speed of about 3.3 AU per year. At that distance, signals from Voyager take just over 14 hours and 4 minutes to reach us.

See images from Voyager 2’s visit of Uranus here, and check out a video of the August 20, 1977 launch below along with more images from the historic Voyager mission’s “Grand Tour” of the outer Solar System.

Voyager 1 May Have Left the Solar System

Number of particles from the Sun hitting Voyager 1. Credit: NASA

While there’s no official word from NASA on this, the buzz around the blogosphere is that Voyager 1 has left the Solar System. The evidence comes from this graph, above, which shows the number of particles, mainly protons, from the Sun hitting Voyager 1 across time. A huge drop at the end of August hints that Voyager 1 may now be in interstellar space. The last we heard from the Voyager team was early August, and they indicated that on July 28, the level of lower-energy particles originating from inside our Solar System dropped by half. However, in three days, the levels had recovered to near their previous levels. But then the bottom dropped out at the end of August.

The Voyager team has said they have been seeing two of three key signs of changes expected to occur at the boundary of interstellar space. In addition to the drop in particles from the Sun, they’ve also seen a jump in the level of high-energy cosmic rays originating from outside our Solar System.

The third key sign would be the direction of the magnetic field. No word on that yet, but scientists are eagerly analyzing the data to see whether that has, indeed, changed direction. Scientists expect that all three of these signs will have changed when Voyager 1 has crossed into interstellar space.

“These are thrilling times for the Voyager team as we try to understand the quickening pace of changes as Voyager 1 approaches the edge of interstellar space,” said Edward Stone, the Voyager project scientist for the entire mission, who was quoted in early August. “We are certainly in a new region at the edge of the solar system where things are changing rapidly. But we are not yet able to say that Voyager 1 has entered interstellar space.”

Stone added that the data are changing in ways that the team didn’t expect, “but Voyager has always surprised us with new discoveries.”

Voyager 1 launched on Sept. 5, 1977, is approximately 18 billion kilometers (11 billion miles) from the Sun. Voyager 2, which launched on Aug. 20, 1977, is close behind, at 15 billion km (9.3 billion miles) from the Sun.

Sources: NASA, Eric Berger/ Houston Chronicle, Scientific American

35 Years Ago: Our First Family Portrait of the Earth and Moon

A crescent Earth and Moon as seen by Voyager 1 on September 18, 1977 (NASA)

35 years ago today, September 18, 1977, NASA’s Voyager 1 spacecraft turned its camera homeward just about two weeks after its launch, capturing the image above from a distance of 7.25 million miles (11.66 million km). It was the first time an image of its kind had ever been taken, showing the entire Earth and Moon together in a single frame, crescent-lit partners in space.

The view of Earth shows eastern Asia, the western Pacific Ocean and part of the Arctic. Voyager 1 was actually positioned directly above Mt. Everest when the images were taken (the final color image was made from three separate images taken through color filters.)

The Moon was brightened in the original NASA images by a factor of three, simply because Earth is so much brighter that it would have been overexposed in the images were they set to expose for the Moon. (Also I extended the sides of the image a bit above to fit better within a square format.)

Read the latest on Voyager 1: Winds of Change at the Edge of the Solar System

Previous images may have shown the Earth and Moon together, but they were taken from orbit around one or the other and as a result didn’t have both worlds fully — and in color! — within a single frame like this one does. In fact, it was only 11 years earlier that the very first image of Earth from the Moon was taken, acquired by NASA’s Lunar Orbiter I spacecraft on August 23, 1966.

It’s amazing to think what was happening in the world when Voyager took that image:
• World population was 4.23 billion (currently estimated to be 7.04 billion)
• The Space Shuttle Enterprise made its first test flight from a 747
• Star Wars, Close Encounters of the Third Kind and Saturday Night Fever were out in U.S. theaters
• Charlie Chaplin and Elvis Presley died
• U.S. federal debt was “only” $706 billion (now over $16 trillion!)
• And, of course, both Voyagers launched on their Grand Tour of the Solar System, ultimately becoming the most distant manmade objects in existence
(See more world stats and events here.)


“Once a photograph of the Earth, taken from outside, is available – once the sheer isolation of the Earth becomes known – a new idea as powerful as any in history will be let loose.”
– Sir Fred Hoyle

Is Triton Hiding an Underground Ocean?

Voyager 2 mosaic of Neptune’s largest moon, Triton (NASA)

At 1,680 miles (2,700 km) across, the frigid and wrinkled Triton is Neptune’s largest moon and the seventh largest in the Solar System. It orbits the planet backwards – that is, in the opposite direction that Neptune rotates – and is the only large moon to do so, leading astronomers to believe that Triton is actually a captured Kuiper Belt Object that fell into orbit around Neptune at some point in our solar system’s nearly 4.7-billion-year history.

Briefly visited by Voyager 2 in late August 1989, Triton was found to have a curiously mottled and rather reflective surface nearly half-covered with a bumpy “cantaloupe terrain” and a crust made up of mostly water ice, wrapped around a dense core of metallic rock. But researchers from the University of Maryland are suggesting that between the ice and rock may lie a hidden ocean of water, kept liquid despite estimated temperatures of  -97°C (-143°F), making Triton yet another moon that could have a subsurface sea.

How could such a chilly world maintain an ocean of liquid water for any length of time? For one thing, the presence of ammonia inside Triton would help to significantly lower the freezing point of water, making for a very cold — not to mention nasty-tasting — subsurface ocean that refrains from freezing solid.

In addition to this, Triton may have a source of internal heat — if not several. When Triton was first captured by Neptune’s gravity its orbit would have initially been highly elliptical, subjecting the new moon to intense tidal flexing that would have generated quite a bit of heat due to friction (not unlike what happens on Jupiter’s volcanic moon Io.) Although over time Triton’s orbit has become very nearly circular around Neptune due to the energy loss caused by such tidal forces, the heat could have been enough to melt a considerable amount of water ice trapped beneath Triton’s crust.

Related: Titan’s Tides Suggest a Subsurface Sea

Another possible source of heat is the decay of radioactive isotopes, an ongoing process which can heat a planet internally for billions of years. Although not alone enough to defrost an entire ocean, combine this radiogenic heating with tidal heating and Triton could very well have enough warmth to harbor a thin, ammonia-rich ocean beneath an insulating “blanket” of frozen crust for a very long time — although eventually it too will cool and freeze solid like the rest of the moon. Whether this has already happened or still has yet to happen remains to be seen, as several unknowns are still part of the equation.

“I think it is extremely likely that a subsurface ammonia-rich ocean exists in Triton,” said Saswata Hier-Majumder at the University of Maryland’s Department of Geology, whose team’s paper was recently published in the August edition of the journal Icarus. “[Yet] there are a number of uncertainties in our knowledge of Triton’s interior and past which makes it difficult to predict with absolute certainty.”

Still, any promise of liquid water existing elsewhere in large amounts should make us take notice, as it’s within such environments that scientists believe lie our best chances of locating any extraterrestrial life. Even in the farthest reaches of the Solar System, from the planets to their moons, into the Kuiper Belt and even beyond, if there’s heat, liquid water and the right elements — all of which seem to be popping up in the most surprising of places — the stage can be set for life to take hold.

Read more about this here on

Inset image: Voyager 2 portrait of Neptune and Triton taken on August 28, 1989. (NASA)

Winds of Change at the Edge of the Solar System

As the venerable Voyager 1 spacecraft hurtles ever outward, breaking through the very borders of our solar system at staggering speeds upwards of 35,000 mph, it’s sending back information about the curious region of space where the Sun’s outward flow of energetic particles meets the more intense cosmic radiation beyond — a boundary called the heliosheath.

Voyager 1 has been traveling through this region for the past seven years, all the while its instruments registering gradually increasing levels of cosmic ray particles. But recently the levels have been jumping up and down, indicating something new is going on… perhaps Voyager 1 is finally busting through the breakers of our Sun’s cosmic bay into the open ocean of interstellar space?

Data sent from Voyager 1 — a trip that currently takes the information nearly 17 hours to make — have shown steadily increasing levels of cosmic radiation as the spacecraft moves farther from the Sun. But on July 28, the levels of high-energy cosmic particles detected by Voyager jumped by 5 percent, with levels of lower-energy radiation from the Sun dropping by nearly half later the same day. Within three days both levels had returned to their previous states.

The last time such a jump in levels occurred was in May — and that spike took a week to happen.

“The increase and the decrease are sharper than we’ve seen before, but that’s also what we said about the May data,” said Edward Stone, the Voyager project scientist based at the California Institute of Technology. “The data are changing in ways that we didn’t expect, but Voyager has always surprised us with new discoveries.”

The graph below shows the jump in cosmic particles detected starting May 2012.

Over 11 billion miles (18 billion km) from home, Voyager 1 has been cruising through space since its launch on September 5, 1977. Its twin, Voyager 2, was launched two weeks earlier and is currently 9.3 billion miles (15 billion km) away. Both spacecraft are healthy and continue to communicate with Earth, and will both eventually break through the borders of our solar system and enter true interstellar space. If they are still operational when that happens — and there’s no reason that they shouldn’t be — we will finally get a sense of what conditions are like “out there”.

Although Voyager 1 is registering intriguing fluctuations in radiation from both inside and outside the Solar System, it’s not quite there yet.

“Our two veteran Voyager spacecraft are hale and healthy as they near the 35th anniversary of their launch,” said Suzanne Dodd, Voyager project manager based at JPL in Pasadena. “We know they will cross into interstellar space. It’s just a question of when.”

Read more about Voyager’s ongoing breakout here.

“We are certainly in a new region at the edge of the solar system where things are changing rapidly. But we are not yet able to say that Voyager 1 has entered interstellar space.”

–  Edward Stone, Voyager project scientist, Caltech

Images: NASA/JPL-Caltech

Voyager 1 Breaking Through the Borders of the Solar System

After almost 35 years traveling at over 35,000 mph, the venerable (and still operational!) Voyager 1 spacecraft is truly breaking through to the other side, crossing the outermost boundaries of our solar system into interstellar space — over 11 billion miles from home.

Data received from Voyager 1 — a trip that currently takes the information 16 hours and 38 minutes to make — reveal steadily increasing levels of cosmic radiation, indicating that the spacecraft is leaving the relatively protected bubble of the Sun’s influence and venturing into the wild and wooly space beyond.

From the JPL press release:

“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,” said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. “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.”

The data making the 16-hour-38 minute, 11.1-billion-mile (17.8-billion-kilometer), journey from Voyager 1 to antennas of NASA’s Deep Space Network on Earth detail the number of charged particles measured by the two High Energy telescopes aboard the 34-year-old spacecraft. These energetic particles were generated when stars in our cosmic neighborhood went supernova.

“From January 2009 to January 2012, there had been a gradual increase of about 25 percent in the amount of galactic cosmic rays Voyager was encountering,” said Stone. “More recently, we have seen very rapid escalation in that part of the energy spectrum. Beginning on May 7, the cosmic ray hits have increased five percent in a week and nine percent in a month.”

This marked increase is one of a triad of data sets which need to make significant swings of the needle to indicate a new era in space exploration. The second important measure from the spacecraft’s two telescopes is the intensity of energetic particles generated inside the heliosphere, the bubble of charged particles the sun blows around itself. While there has been a slow decline in the measurements of these energetic particles, they have not dropped off precipitously, which could be expected when Voyager breaks through the solar boundary.

“When the Voyagers launched in 1977, the space age was all of 20 years old. Many of us on the team dreamed of reaching interstellar space, but we really had no way of knowing how long a journey it would be — or if these two vehicles that we invested so much time and energy in would operate long enough to reach it.”

– Ed Stone, Voyager project scientist, Caltech

Read more on the JPL site here.

Addition: Check out the accompanying video from [email protected] below:

Top image: Artist’s concept showing NASA’s two Voyager spacecraft exploring a turbulent region of space known as the heliosheath, the outer shell of the bubble of charged particles around our sun. Credit: NASA/JPL-Caltech. Secondary image: Artist’s concept of NASA’s Voyager spacecraft. Credit: NASA/JPL-Caltech.