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Voyager Makes an Interstellar Discovery

eaglewingone

Alphans
The solar system is passing through an interstellar cloud that physics says should not exist. In the Dec. 24th issue of Nature, a team of scientists reveal how NASA's Voyager spacecraft have solved the mystery.

"Using data from Voyager, we have discovered a strong magnetic field just outside the solar system," explains lead author Merav Opher, a NASA Heliophysics Guest Investigator from George Mason University. "This magnetic field holds the interstellar cloud together and solves the long-standing puzzle of how it can exist at all."


The discovery has implications for the future when the solar system will eventually bump into other, similar clouds in our arm of the Milky Way galaxy.

Astronomers call the cloud we're running into now the Local Interstellar Cloud or "Local Fluff" for short. It's about 30 light years wide and contains a wispy mixture of hydrogen and helium atoms at a temperature of 6000 C. The existential mystery of the Fluff has to do with its surroundings. About 10 million years ago, a cluster of supernovas exploded nearby, creating a giant bubble of million-degree gas. The Fluff is completely surrounded by this high-pressure supernova exhaust and should be crushed or dispersed by it.

"The observed temperature and density of the local cloud do not provide enough pressure to resist the 'crushing action' of the hot gas around it," says Opher.

So how does the Fluff survive? The Voyagers have found an answer.

"Voyager data show that the Fluff is much more strongly magnetized than anyone had previously suspected—between 4 and 5 microgauss*," says Opher. "This magnetic field can provide the extra pressure required to resist destruction."


NASA's two Voyager probes have been racing out of the solar system for more than 30 years. They are now beyond the orbit of Pluto and on the verge of entering interstellar space—but they are not there yet.

"The Voyagers are not actually inside the Local Fluff," says Opher. "But they are getting close and can sense what the cloud is like as they approach it."

The Fluff is held at bay just beyond the edge of the solar system by the sun's magnetic field, which is inflated by solar wind into a magnetic bubble more than 10 billion km wide. Called the "heliosphere," this bubble acts as a shield that helps protect the inner solar system from galactic cosmic rays and interstellar clouds. The two Voyagers are located in the outermost layer of the heliosphere, or "heliosheath," where the solar wind is slowed by the pressure of interstellar gas.

Voyager 1 entered the heliosheath in Dec. 2004; Voyager 2 followed almost 3 years later in Aug. 2007. These crossings were key to Opher et al's discovery.


The size of the heliosphere is determined by a balance of forces: Solar wind inflates the bubble from the inside while the Local Fluff compresses it from the outside. Voyager's crossings into the heliosheath revealed the approximate size of the heliosphere and, thus, how much pressure the Local Fluff exerts. A portion of that pressure is magnetic and corresponds to the ~5 microgauss Opher's team has reported in Nature.

The fact that the Fluff is strongly magnetized means that other clouds in the galactic neighborhood could be, too. Eventually, the solar system will run into some of them, and their strong magnetic fields could compress the heliosphere even more than it is compressed now. Additional compression could allow more cosmic rays to reach the inner solar system, possibly affecting terrestrial climate and the ability of astronauts to travel safely through space. On the other hand, astronauts wouldn't have to travel so far because interstellar space would be closer than ever. These events would play out on time scales of tens to hundreds of thousands of years, which is how long it takes for the solar system to move from one cloud to the next.

"There could be interesting times ahead!" says Opher.

http://science.nasa.gov/headlines/y2009/23dec_voyager.htm
 
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VTracy

Alphans
Interesting stuff, thanks for posting:thumbup:

I wished they would've speculated about the effects of leaving the heliosphere on the two spacecraft.

Will the magnetic fields have an effect on them, and their electronics?

How long will these two be able to transmit data? Do they still send pics?
 

eaglewingone

Alphans
Interesting stuff, thanks for posting:thumbup:

I wished they would've speculated about the effects of leaving the heliosphere on the two spacecraft.

Will the magnetic fields have an effect on them, and their electronics?

How long will these two be able to transmit data? Do they still send pics?

I do not think that it would affect their electronics at all.Both spacecraft are still in communication with Earth and relaying data.Remember it takes 15 hours(Voyager 1) and 11 hours(Voyager 2) to send commands to the spacecraft, at the speed of light from Earth.Both spacecraft is suffering of a slow paralysis.It has enough power until 2020-2025 but other things are slowly shutting down. It losing precious hydrazine fuel with keeps it oriented and many of its sub systems have failed.Some systems are being turned "off" because many scientists want to not overload the systems that are working and conserve power.The first will be its gyro stabiliers which is the piece of equipment that keeps the antenna pointing toward Earth will go out around 2015. You can get Voyager updates at this link. As on 12/3/2009, the spacecraft performance was nominal:

http://voyager.jpl.nasa.gov/mission/weekly-reports/index.htm

The last picture it sent was a "family portrait' of the Solar System in 1990.
http://nssdc.gsfc.nasa.gov/photo_gallery/photogallery-solarsystem.html
 
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VTracy

Alphans
Thanks eagle:thumbup:


I guess since the last pic was in 1990, that means no more pics.:cry:

Too bad, I can only imagine what this little craft is seeing now.
 

VTracy

Alphans
Just checked out the site. Wow, 10 billion miles from the sun!!!

Just thinking, 2015 is the arrival time for New Horizons to the Pluto system.
 

eaglewingone

Alphans
Thanks eagle:thumbup:


I guess since the last pic was in 1990, that means no more pics.:cry:

Too bad, I can only imagine what this little craft is seeing now.

Both spacecraft are too far away for photo exposures.The Sun is one of many stars in the background. The Voyager 2 scan platform is also stuck but it can relay data that is useful from other insterments. When it reached Neptune, the Voyager 2 scan platform jammed so they had to take longer photo exposures so they had to use more hydrazine to orient the spacecraft.
 
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