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Hubble mosaic of the Crab Nebula

A Hubble Space Telescope picture of the Crab Nebula, a cloud of dust and gas left over from a supernova.

Image courtesy ESA/NASA

Andrew Fazekas

for National Geographic News

Published January 31, 2012

For the first time, a NASA spacecraft has directly observed "alien" particles that came from beyond our solar system, astronomers announced today.

The discovery not only gives us a glimpse of what exists in the so-called interstellar medium—the matter between stars—but also offers clues to the anatomy of our local galactic neighborhood.

Orbiting Earth some 200,000 miles (322,000 kilometers) away, the Interstellar Boundary Explorer (IBEX) spacecraft was able to snag samples of hydrogen, oxygen, and neon that came from interstellar space.

"It's exciting to be able to have these first observations of alien matter—stuff that didn't come from our sun or the planets, but came from the outside of our solar system, from other parts of the galaxy," David McComas, team leader for the IBEX program, said during a NASA news conference Tuesday.

"We think these are really important measurements, because these elements are the fundamental building blocks of stars, planets, and people."

(Related: "Solar System's 'Nose' Found; Aimed at Constellation Scorpius.")

IBEX Find a "15-Billion-Mile Hole-in-One"

Since its launch in October 2008, the IBEX probe has been mapping the boundary of the solar system, called the heliosphere.

This bubble in the Milky Way galaxy is created by solar wind, which is the stream of charged particles that's constantly blowing out from the sun in all directions.

The edge of the heliosphere lies about a hundred times farther from us than Earth does from the sun, and it shields the inner solar system from deadly cosmic radiation.

That's because the heliosphere and its associated magnetic field push away damaging charged particles. These particles—remnants from supernovae that are dispersed through interstellar space—flow toward us at 50,000 miles (80,000 kilometers) an hour.

(Also see "Frothy Magnetic-Bubble Sea Found at Solar System's Edge.")

But half of the particles in the interstellar wind are neutral, and these uncharged atoms can make it into our solar system.

A few of these neutral hydrogen, oxygen, and neon particles then made it all the way to Earth, where IBEX was able to detect them, McComas said during the conference.

"I like to call it the 15-billion-mile [24-billion-kilometer] hole-in-one," he said.

Solar System Rich in Oxygen?

An analysis of the new IBEX data compared the ratios of oxygen to neon from interstellar space with the ratios of these atoms native to our solar system.

The results show that our solar system appears to contain more oxygen than surrounding interstellar space.

This may mean that our solar system migrated to its current location from a more oxygen-rich environment. Or it's possible a lot of oxygen is trapped within dust grains or ice in the interstellar medium.

(Related: "Mystery Space 'Ribbon' Found at Solar System's Edge.")

IBEX also measured the speed of the interstellar wind, revealing that the wind is moving about 7,000 miles (11,000 kilometers) an hour slower than previously recorded.

Combined with previous data on nearby interstellar clouds—gossamer blobs of gas and dust many light-years across—the team was able to more precisely pinpoint our location in the local galactic neighborhood.

Our solar system appears to sit at the edge of one of many low-density interstellar clouds that move through this region of the galaxy—and we may actually exit the cloud in the next few thousand years, the data show.

"It's so exciting to know where our sun is in relation to local clouds. It really puts our sun in context for the first time," said Seth Redfield, an astronomer from Wesleyan University in Middletown, Connecticut, who's involved with IBEX.

"Our location within our local interstellar cloud is important," Redfield added, "because the heliosphere structure changes depending on where it is inside a cloud or outside, and so it has consequences for how well it shields us from those deadly cosmic rays."

The new IBEX results appear in a series of papers in the February edition of Astrophysical Journal Supplements.

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