Voyager Makes an Interstellar Discovery

Science@NASA ^ | 12.23.2009 | Dr. Tony Phillips

[PeaceBeWithYou]

December 23, 2009: 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.

To read the original research, look in the Dec. 24, 2009, issue of Nature for Opher et al's article, "A strong, highly-tilted interstellar magnetic field near the Solar System."

[PeaceBeWithYou]

Right out of Roddenberry's Star Trek.

Clickable pics open in a new window

Voyager flies through the outer bounds
of the heliosphere en route to interstellar
space. A strong magnetic field reported by
Opher et al in the Dec. 24, 2009, issue of
Nature is delineated in yellow.

An artist's concept of the Local Interstellar Cloud,
also known as the "Local Fluff."

The anatomy of the heliosphere. Since
this illustration was made, Voyager 2
has joined Voyager 1 inside the heliosheath,
a thick outer layer where the solar wind is
slowed by the pressure of interstellar gas.

[allmost]

Archaic tech. Let’s try again :)

[The Drowning Witch]

My God....We’re motes of sand a-drift in a river the size of the Mississippi.

[DesertSapper]

"an interstellar cloud that physics says should not exist"

Then it must not be there because physicists know everything!

[Frantzie]

VeeGer is still sending back data? Didn’t another one leave the solar system?

[GeronL]

cool!!

Solar Systems are like bubbles in the fluff!

[Skooz]

bfl

[Blood of Tyrants]

We are less than that.

[SaxxonWoods]

“There could be interesting times ahead!” says Opher.

There should be elaboration upon such a statement. This isn’t the Perils of Pauline. Or is it?

[dog breath]

Massive amounts of hot air and fluff, at first I thought this was another article about Obama.

[ProtectOurFreedom]

Thanks for posting. This really hits home for me as my Dad lead the program to develop and manufacture the powerplants that power Voyager 1 and 2. I really enjoy reading about these amazing spacecraft.

[buccaneer81]

Space ping!

[colinhester]

How cool!

[The Magical Mischief Tour]

Then it must not be there because physicists know everything!

No... that would be Algore.

[jonrick46]

Does this mean that we have to traverse a 4000 degree “fluff” zone on our way out of the solar system? That appears like this is an impenetrable zone that keeps man trapped inside the solar system.

[El Sordo]

If only we were that big.

[Centurion2000]

Best $$ ever spent on a space probe ... 30+ years and STILL working ... paid in full.

[Nik Naym]

“Then it must not be there because physicists know everything! “

That’s funny, physicists will be the first to tell you that they do not.

[Centurion2000]

My God....We’re motes of sand a-drift in a river the size of the Mississippi.

Less than that. If the sun were a basketball in New Orleans, the nearest star would be a basketball ..... in Moscow, Russia.

[Pan_Yan]

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