NASA spacecraft reveals new observations of interstellar matter
February 1, 2012
A great magnetic bubble surrounds the solar system as it cruises through the galaxy. The sun pumps the inside of the bubble full of solar particles that stream out to the edge until they collide with the material that fills the rest of the galaxy, at a complex boundary called the heliosheath. On the other side of the boundary, electrically charged particles from the galactic wind blow by, but rebound off the heliosheath, never to enter the solar system. Neutral particles, on the other hand, are a different story. They saunter across the boundary as if it weren't there, continuing on another 7.5 billion miles for 30 years until they get caught by the sun's gravity, and sling shot around the star. There, NASA's Interstellar Boundary Explorer lies in wait for them ... (Credit: NASA)
NASA’s Interstellar Boundary Explorer (IBEX) has captured the best and most complete glimpse yet of what lies beyond the solar system.
The new measurements give clues about how and where our solar system formed, the forces that physically shape our solar system, and the history of other stars in the Milky Way.
The Earth-orbiting spacecraft observed four separate types of atoms including hydrogen, oxygen, neon and helium. These interstellar atoms are the byproducts of older stars, which spread across the galaxy and fill the vast space between stars.
IBEX determined the distribution of these elements outside the solar system, which are flowing charged and neutral particles that blow through the galaxy, or the so-called interstellar wind.
In a series of science papers appearing in the Astrophysics Journal on Jan. 31, scientists report finding 74 oxygen atoms for every 20 neon atoms in the interstellar wind. In our own solar system, there are 111 oxygen atoms for every 20 neon atoms. This translates to more oxygen in any part of the solar system than in nearby interstellar space.
NASA's Interstellar Boundary Explorer (IBEX) studies the outer boundaries of the solar system, where particles from the solar wind collide with particles from the galactic wind (credit: NASA)
“Our solar system is different than the space right outside it, suggesting two possibilities,” says David McComas, IBEX principal investigator, at the Southwest Research Institute in San Antonio.
“Either the solar system evolved in a separate, more oxygen-rich part of the galaxy than where we currently reside, or a great deal of critical, life-giving oxygen lies trapped in interstellar dust grains or ices, unable to move freely throughout space.”
The new results hold clues about the history of material in the universe. While the big bang initially created hydrogen and helium, only the supernovae explosions at the end of a star’s life can spread the heavier elements of oxygen and neon through the galaxy. Knowing the amounts of elements in space may help scientists map how our galaxy evolved and changed over time.
Exploring the interstellar medium
Scientists want to understand the composition of the boundary region that separates the nearest reaches of our galaxy, called the local interstellar medium, from our heliosphere. The heliosphere acts as a protective bubble that shields our solar system from most of the dangerous galactic cosmic radiation that otherwise would enter the solar system from interstellar space.
IBEX measured the interstellar wind traveling at a slower speed than previously measured by the Ulysses spacecraft, and from a different direction. The improved measurements from IBEX show a 20 percent difference in how much pressure the interstellar wind exerts on our heliosphere.
“Measuring the pressure on our heliosphere from the material in the galaxy and from the magnetic fields out there will help determine the size and shape of our solar system as it travels through the galaxy,” says Eric Christian, IBEX mission scientist, at NASA’s Goddard Space Flight Center in Greenbelt, Md.
The IBEX spacecraft was launched in October 2008. Its science objective is to discover the nature of the interactions between the solar wind and the interstellar medium at the edge of our solar system.
The galactic wind streams toward the sun from the direction of Scorpio and IBEX has found that it travels at 52,000 miles an hour. The speed of the galactic wind and its subsequent pressure on the outside of the solar system's boundary affects the shape of the heliosphere as it travels through space (credit: NASA/Goddard Scientific Visualization Studio)
The Southwest Research Institute developed and leads the IBEX mission with a team of national and international partners.
The spacecraft is one of NASA’s series of low-cost, rapidly developed missions in the Small Explorers Program. Goddard manages the program for the agency’s Science Mission Directorate at NASA Headquarters in Washington.
Among the six U.S. institutions on the IBEX mission are the University of New Hampshire (UNH), the LMATC, SwRI, the University of Texas, San Antonio, MIT, and the University of Chicago.
See also:
February issue of The Astrophysical Journal Supplement Series (written by IBEX team members)
IBEX: Glimpses of the Interstellar Material Beyond our Solar System (NASA)
IBEX Team, UNH Scientist Present Mission Findings Today at NASA Press Conference (UNH)
