Tag Archives: Voyager-1

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Voyager may have already left the solar system according to magnetic bubble theory

voyager-1 probe

Our farthest scout in the Universe, the Voyager-1 probe, has traveled some 18.7 billion kilometers so far and it doesn’t show any sign of stopping. Soon enough, it will be the first man-made object to leave our solar system, when exactly however has been a matter of debate. For the past year or so, contradictory claims have made the matter uncertain, and officially (the word from the Voyager team) the craft has yet to breach the final outer limits of the solar system. A new paper, however,  suggests that the probe may have already left our solar system by offering a different interpretation on the magnetic bubble Voyager is currently traveling through.

Its rather difficult to draw a line where the solar system ends and where interstellar space begins. If we’re to judge from the heliosphere’s perspective – a bubble-like enclosure dominated by charged particles coming from the sun – we might very well say that Voyager’s way out since the number of particles of interstellar origin far outnumber those coming from the sun.

Beyond this region lies another region of contact, this time of a magnetic order. Referred to as the “magnetic highway”, in this region our sun’s magnetic field lines are connected to interstellar magnetic field lines. The problem is we don’t know for sure what happens at the junction between interstellar and solar magnetic fields. If you will, it’s like as if you were an European explorer in the XXVth century and you just set foot in the Americas – you have no idea what you’ll get, what you’ll see next until actually do.

The most distant man-made object

The main hypothesis is that magnetic fields are oriented in different directions inside and outside the bubble, and so far Voyager has yet to exhibit the sharp change in direction everyone’s expecting once it fully exits the solar system. Marc Swisdak and colleagues at University of Maryland propose an explanation that would account for the lack of change in direction, while at the same time hinting towards Voyager’s exit. They claim that the magnetic fields at the interstellar boundary may actually be parallel, and if this is the case scientists shouldn’t need to see a variation in direction.

voyager-one-solar-system

This magnetic parallelism would be caused by a phenomenon called magnetic reconnection, in which magnetic field lines break and then recombine in a sort of violently popping action. Magnetic reconnection is also thought to power solar flares. They envision a pair of magnetic ‘islands’ that appear spontaneously near three reconnection sites. Together these phenomena combine to create a set of parallel magnetic field lines that are just outside the Solar System proper.

With this in mind, the researchers performed a magnetohydrodynamics simulation done at NASA’s Ames research center in Moffett Field, California which offered these findings. These were presented recently at the American Geophysical Union meeting in Mexico, however, according to the authors people there had a hard time “swallowing this scenario.”

“The fine-scale magnetic connection model,” said  Ed Stone of the California Institute of Technology, “will become part of the discussion among scientists as they try to reconcile what may be happening on a fine scale with what happens on a larger scale.”

Stone has been the lead scientist for the Voyager mission ever since the probe first launched more than 35 years ago. He’s the guy who will blow the final whistle signaling the probe has left the solar system. When this will happen? Most likely within a few months (of course if it hasn’t left it already!), but like stated earlier, this is a whole new ground we’re treading about. Sure, we have a fairly good idea what we’re going to physically meet and measure beyond our solar system – it’s not like walking blindfolded – still, it wouldn’t be entirely surprising if Voyager would need years to leave the solar system.

The magnetic reconnection paper was published in the Journal of Astrophysical Letters.

 

After 34 years in space, Voyager has finally left the solar system

To boldly go where no man has gone before: a spacecraft launched from Earth, Voyager I has pushed into the great unknown, leaving behind our solar system.

For years, astronomers have been discussing about when Voyager will finally leave the solar system – and it’s actually pretty hard to draw a line and say that this is where our solar system ends.

voyager

You can track Voyager’s distance to the Sun and the Earth using this resource. If you’re wondering why the distance to Earth is decreasing, it’s because right now, the Earth is orbiting in its direction, and its doing so faster than the shuttle is moving.

Wednesday morning, the official word came down: interstellar space travel has been reached. The announcement came through a press release from the American Geophysical Union:

Thirty-five years after its launch, Voyager 1 appears to have travelled beyond the influence of the Sun and exited the heliosphere, according to a new study appearing online today.

The heliosphere is a region of space dominated by the Sun and its wind of energetic particles, and which is thought to be enclosed, bubble-like, in the surrounding interstellar medium of gas and dust that pervades the Milky Way galaxy.

On August 25, 2012, NASA’s Voyager 1 spacecraft measured drastic changes in radiation levels, more than 11 billion miles from the Sun. Anomalous cosmic rays, which are cosmic rays trapped in the outer heliosphere, all but vanished, dropping to less than 1 percent of previous amounts. At the same time, galactic cosmic rays – cosmic radiation from outside of the solar system – spiked to levels not seen since Voyager’s launch, with intensities as much as twice previous levels.

The findings have been accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union.

“Within just a few days, the heliospheric intensity of trapped radiation decreased, and the cosmic ray intensity went up as you would expect if it exited the heliosphere,” said Bill Webber, professor emeritus of astronomy at New Mexico State University in Las Cruces. He calls this transition boundary the “heliocliff.”

In the GRL article, the authors state: “It appears that [Voyager 1] has exited the main solar modulation region, revealing [hydrogen] and [helium] spectra characteristic of those to be expected in the local interstellar medium.”

However, Webber notes, scientists are continuing to debate whether Voyager 1 has reached interstellar space or entered a separate, undefined region beyond the solar system.

“It’s outside the normal heliosphere, I would say that,” Webber said. “We’re in a new region. And everything we’re measuring is different and exciting.”

The work was funded by NASA’s Jet Propulsion Laboratory in Pasadena, Calif.

This artist's concept shows 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. After more than 33 years of travel, the two Voyager spacecraft will soon reach interstellar space, which is the space between stars. (c) NASA

Voyager-1 discovers new solar system boundary as it heads for interstellar space

This artist's concept shows 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. After more than 33 years of travel, the two Voyager spacecraft will soon reach interstellar space, which is the space between stars.  (c) NASA

This artist’s concept shows 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. After more than 33 years of travel, the two Voyager spacecraft will soon reach interstellar space, which is the space between stars. (c) NASA

The Voyager probes have provided scientists with invaluable data for the past four decades as they circled our solar system’s outmost planets, and most importantly as they prepare to leave our solar system. Though expected to exit the solar system by the end of this year, Voyager-1 has yet to achieve this. The reason for this, scientists say, is that the probe has reached a new boundary between interstellar space and the heliosphere that hadn’t been predicted.

As Voyager-1 nears the heliopause – the region of space where the sun’s influence can no longer be felt and interstellar space starts – readings should have recorded  fewer particles of solar wind and more cosmic rays pouring in from interstellar space. And indeed this is how events actually flowed, as 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.

Things were a bit hectic, with solar wind particle levels rising and dropping for a while in spikes, however a clear trend of solar influence dwindling could be determined. From late July until today,  the intensity of the solar wind particles had decreased a thousand-fold, while cosmic ray intensities rose.

Nature doesn’t act as expected

If everything went as predicted, where’s surprising new boundary then? Well, were scientists to look solely at charged particles reading, they would have determined that Voyager-1 had cleared the solar system and entered interstellar medium.

The sun creates a solar magnetic field wrapping the solar system like a bubble. As Voyager-1 headed for the heliopause scientists predicted that the magnetic field would first shift directions, then be left behind and the interstellar one would be detected.

Voyager’s instruments have yet to detect any anticipated change in field direction, according to Leonard Burlaga, a member of the team that operates Voyager’s magnetometer from NASA’s Goddard Space Flight Center in Greenbelt, Md.

“As ever, Voyager seems to have a remarkable capacity for providing observations that suggest … we’re almost right,” said Gary Zank, a space physicist at the University of Alabama-Huntsville. “It would be nice for the theory and the observations to agree all at once. But it may not ever happen that way.”

Now, scientists conclude that the probe has reached a new interstellar boundary that nobody had predicted. It is in this area that the solar system’s magnetic field links with that of interstellar space, a bridge which scientists now call a  “highway” that allows particles from both mediums to travel along.

No model had predicted this new boundary in the heliosheath, so now astronomers can’t tell for sure when Voyager-1, which is 11 billion miles from the sun and is currently the most distant man-made object in space, will exit the solar system. Voyager-2 is trailing behind, some 2 billion miles away from Voyager-1, and hasn’t reached this region yet.

Both probes are powered by a nuclear core fueled by radioactive plutonium-238, will begin powering down in 2020 and are expected to stop operating in 2025. Still, scientists are confident that both probes should well exit the solar system by then.

The results were announced during a press conference at the recent American Geophysical Union meeting.

A proposed deep-space probe to Jupiter that uses the radioactive nuclear engine proposed at NASA and Los Alamos. (c) Los Alamos National Laboratory

Fission nuclear engines tested for deep space flight

A proposed deep-space probe to Jupiter that uses the radioactive nuclear engine proposed at NASA and Los Alamos. (c) Los Alamos National Laboratory

A proposed deep-space probe to Jupiter that uses the radioactive nuclear engine proposed at NASA and Los Alamos. (c) Los Alamos National Laboratory

Scientists at the Los Alamos National Laboratory have successfully tested out the prototype for a nuclear-reactor engine, meant to serve in the future as an  “a simple, reliable space power system.” Although the experiment, dubbed Demonstration Using Flattop Fissions (DUFF), rendered only 24 watts of power, barely enough to power a common household light bulb, the system can obviously be scaled and provide basic footing for future space exploration probes or even spacecraft design for deep space.

To me at least, it’s rather curious how simple the system is. The small nuclear reactor is powered by uranium and acts a Stirling engine, which most of you motor-heads out there are more than familiarized with. Invented in 19th century, the Stirling engine provides mechanical energy which can then be converted in electricity, for instance, from a simple to-and-fro movement of a pressurized piston. Cooling is ensured by a, yet again, simple heat pipe, which is also used extensively in electronics cooling. That’s no warp-drive, folks.

The researchers claim a 50-pound hunk of enriched uranium that sits inside a 12-inch reactor core could power eight Stirling engines to produces as much as 500 watts of power. This is the first space-orientated nuclear reactor experiment since 1965. Around that time NASA launched the nuclear powered Voyager-1 and Voyager-2, and to this day they remain operational. In fact, Voyager-1 is on the brink of reaching interstellar space, which would officially make it the first man-made object to leave our solar system.

“The heat pipe and Stirling engine used in this test are meant to represent one module that could be used in a space system,” Marc Gibson of NASA Glenn Research Center said a Los Alamos statement. “A flight system might use several modules to produce approximately one kilowatt of electricity.”

The Voyager probes however run on plutonium-238, and since 1992 the US has currently no means of producing plutonium-238 anymore. Uranium on the other hand is fairly abundant.

Applications for the nuclear-engine would be numerous, from reliable space probes that can go on for decades or more sophisticated deep space satellites that can afford the energy cost of sophisticated instruments. It’s rather peculiar that both the DOE and NASA have invested so little in space applications powered by nuclear energy. The video below illustrates the Los Alamos scientists’ small nuclear reactor capabilities.


via Wired

 

The two faces of Uranus as seen through the adaptive optics on the near-infrared camera of the Keck II telescope in Hawaii. (c) Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater.

Most detailed observations of Uranus reveal complex atmospheric patterns

The most detailed observations of the icy world of Uranus, the seventh planet from the sun, show complex weather patterns and other features that scientists have yet to fully describe.

The two faces of Uranus as seen through the adaptive optics on the near-infrared camera of the Keck II telescope in Hawaii. (c) Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater.

The two faces of Uranus as seen through the adaptive optics on the near-infrared camera of the Keck II telescope in Hawaii. (c) Lawrence Sromovsky, Pat Fry, Heidi Hammel, Imke de Pater.

Popular belief had Uranus depicted as a bland, pale green world based on the now iconic observations from Voyager’s 1986 flyby of the planet. Its instruments from the time, however, weren’t sensitive enough to catch a more in-depth view, and since the planet is 30 times farther away from the sun than Earth, ground based telescopes couldn’t peel through its atmosphere because of noise.

A novel technique employed by an international team of scientists with telescopes of the Keck Observatory allowed for the first most detailed view of Uranus by  combining multiple images of the planet in near-infrared. Thus, the scientists were able to reduce the noise and image weather features that are otherwise obscure, and these couldn’t be more interesting. Observations reveal circulating clouds, enormous hurricanes, and an unusual swarm of convective features at its north pole.

“These images reveal an astonishing amount of complexity in Uranus’ atmosphere,” said Heidi Hammel of the Association of Universities for Research in Astronomy. “We knew the planet was active, but until now, much of the activity had been masked by the noise in the data.”

A 2007 image of Uranus from the Keck telescope shows far less surface detail. Image courtesy of Imke de Pater.UC Berkeley.

A 2007 image of Uranus from the Keck telescope shows far less surface detail. Image courtesy of Imke de Pater.UC Berkeley.

The planet, in fact, looks like many of the solar system’s other large planets — the gas giants Jupiter and Saturn, and the ice giant Neptune — said Imke de Pater, professor and chair of astronomy at the University of California, Berkeley, and one of the team members.

Also atmospheric composition has been determined in greater detail than ever before, as data shows the clouds, which race at 560 miles per hour, are mainly composed of hydrogen, helium, and methane. This remarkable velocity came as a surprise to the researchers, since the planet is so far away from the sun, and thus should have lower energy available to drive these weather features.

“The sun is 900 times weaker than on Earth, so you don’t have the same intensity of solar energy driving the system as we do here,” said Larry Sromovsky, a planetary scientist at the University of Wisconsin, Madison, who lead the study. “Thus, the atmosphere of Uranus must operate as a very efficient machine with very little dissipation. Yet it undergoes dramatic variations that seem to defy that requirement.”

A distinct feature of Uranus, which greatly influences its now complex weather patterns, is the fact that it’s completely titled on its side. Opposite to how clouds travel from left to right on Earth, for instance, on Uranus the clouds run from up to down. Its North pole is, thus, on the right side. One new feature found by the group is a scalloped band of clouds just south of Uranus’ equator. The band may indicate atmospheric instability or wind shear.

“This is new, and we don’t fully understand what it means,” said Sromovsky. “We haven’t seen it anywhere else on Uranus.”

Like most large weather systems, which are probably much less violent than the storms we know on Earth, Uranus is fairly stable, despite exhibiting some strange patterns.  Some stay at fixed latitudes and undergo large variations in activity, while others have been seen to drift towards the equator, while undergoing great changes in size and shape.

The findings will be presented at the American Astronomical Society’s Division of Planetary Sciences in Reno, Nev.

source: Berkley Uni

Voyager at the edge of the final frontier. Spacecraft expected to exit solar system earlier than thought

It’s remarkably impressive how a spacecraft built and launched in the late 70’s is not only still functional, but well on its way of becoming the first man-made object to leave our solar system. After 35 years, new data shows that this plucky probe may soon cross the undulating boundary between the edge of our solar system and interstellar space.

Artist impression of the Voyager-1 spacecraft, and its partner, Voyager-2, as they’re approaching the edge of the Sun’s protective bubble, separating them from interstellar flight. (c) NASA/JPL-Caltech

The boundary of the solar system has been settled by scientists as the place where the solar wind fizzles out completely – this called the  heliopause. Currently, Voyager-1 is still in the heliosheath where the sun’s solar wind is significantly slowed by the pressure of interstellar gas, but not quite minimal yet. Tantalizing signs now have it that Voyager I, now some 11 billion miles from home, is right near this cosmic milestone for humanity.  Voyager-1′s sister probe, Voyager-2, is currently lagging behind about 2 billion miles

“It’s not that clear because there’s no signpost telling you that you’re now leaving the solar system, but the evidence is mounting that we’re getting really close,” says Arik Posner, a Voyager program scientist at NASA’s headquarters in Washington, D.C.

Voyager’s initial mission in the late 70’s was that of taking first close-up pictures of Jupiter, Saturn, Uranus and Neptune, but apparently it went on going, and it has been for decades now. NASA engineers at the time were apparently invested with some sort of scientific foresight, when they decided to equip the spacecraft with a nuclear power source. Each Voyager is powered by three large radioisotope thermoelectric generators (RTGs), each containing 24 pressed plutonium-238 oxide spheres. The heat released by the decay of the radioactive material is converted into electricity using an array of thermocouples, initially granting around 470 watts of power. The power output of the RTGs does decline over time, though, but the RTGs will continue to support some of its operations through about 2025, more than enough to exit the solar system and transmit data back of what really lies beyond.

“When the Voyagers launched in 1977, the space age was all of 20 years old,” said Mr. Stone. “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.”

via NPR

 

Artist impression of the Voyager-1 spacecraft, and its partner, Voyager-2, as they're approaching the edge of the Sun's protective bubble, separating them from interstellar flight. (c) NASA/JPL-Caltech

Voyager-1 on the brink of interstellar flight

Artist impression of the Voyager-1 spacecraft, and its partner, Voyager-2, as they're approaching the edge of the Sun's protective bubble, separating them from interstellar flight. (c) NASA/JPL-Caltech

Artist impression of the Voyager-1 spacecraft, and its partner, Voyager-2, as they're approaching the edge of the Sun's protective bubble, separating them from interstellar flight. (c) NASA/JPL-Caltech

Launched in in the late 1970’s in a mission to study the planets Jupiter, Saturn and their respective satellites, the two Voyager probes have been most certainly put to a more pioneering goal and sent into outer space after having completed their last missions. Currently, Voyager-1 is the most distant human-made object from Earth and is now quite ready the break the barrier that separates our solar system from interstellar space.

Right now, Voyager is at the so called ‘heliosheath‘ limit, a boundary layer where particles streaming from the Sun clash with the gases of the galaxy.

“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.”

Scientists caught off guard by mixed space environment

Starting from December 2010, reports have indicated that the outward speed of the charged particles streaming from the sun have slowed to almost zero, something entirely unexpected by scientists. This stagnation has continued well thought out February 2011, which physicists now believe this to be a thick “transition zone” at the edge of our solar system. This boundary has caught everybody by surprise, since not even a theory was formulated in which interstellar gases mix with almost zero velocity sun particles. 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.

Voyager-1 should break into interstellar space at any time, computations show

To better understand what kind of environmnet Voyager-1 is heading through, Krimigis and colleagues combined this new Voyager data with similar measurements from the ion and neutral camera on Cassini’s magnetospheric imaging instrument, which collects data on neutral atoms streaming into our solar system from the outside.

What preliminary computations on the data shows is that the boundary layer between interstellar flight and the “solar system bubble” is likely somewhere between 10 and 14 billion miles from the Sun, most likely 11 million miles. Voyager is already 11 billion miles in, which means it could cross into interstellar flight at any time from now on.

“These calculations show we’re getting close, but how close? That’s what we don’t know, but Voyager 1 speeds outward a billion miles every three years, so we may not have long to wait,” said Ed Stone, Voyager project scientist, based at the California Institute of Technology in Pasadena.

MORE RELATED: Harvesting gas from Uranus could power interstellar flight

Soon enough, indeed, Voyager-1 will become the first man made object to completely leave our solar system, and travel far enough as it can. It’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 well before 2020, it will be able to continue its space journey. It is expected to pass the constellation Camelopardalis in around 40,000 years.

Voyager-1’s sister probe, Voyager-2, is currently lagging behind about 2 billion miles but it will also most certainly reach the interstellar barrier in about 6 years.

The new findings have been reported by Krimigis and his colleagues in this week’s edition of Nature.