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Although we can't feel it,
our solar system is constantly being changed by a galactic wind.
The wind is composed of gases like hydrogen, helium, oxygen and
neon, which form a very wispy "atmosphere" between stars.
This gas is called the interstellar medium. Like a bicycle
traveling in a crosswind, the wind that the solar system feels is actually a
combination of a solar system's movement relative to the galaxy and the
movement of the interstellar medium itself. The solar wind
pushes out against this galactic wind, forming a bubble called the heliosphere.
The outer boundary is called the heliopause, and is blown
into a teardrop-shape by the galactic wind. IBEX, or the
Interstellar Boundary Explorer is designed to study this region from Earth
orbit and has now made the first direct measurements of hydrogen,
oxygen and neon from outside the solar system.
Many instruments have seen the characteristic spectra of elements outside the solar
system, but IBEX is actually detecting atoms from interstellar
space that punch through the heliopause and strike the spacecraft.
Only some of the atoms that make up the galactic wind can do this.
Much of the galactic wind is made up of
ions, which are atoms with charge due to missing electrons.
the remaining atoms are neutral; they have the same number of electrons and protons.
The ions are deflected by the magnetic field of the sun,
just like the magnetic field of the Earth deflects the solar wind, but the
neutral atoms are unaffected and go straight through.
The measurement of these atoms by IBEX has enabled scientists to get a better
grasp on the environment around our solar system.
The speed of the galactic wind registered around 52,000 miles per hour,
which is about 12% slower than previously thought. At that speed,
it still takes about 30 years for each atom to reach
IBEX from the edge of the solar system. The IBEX measurements
of heavy interstellar atoms, oxygen and neon, show a
difference from the solar system and galaxy as a whole. This puzzle
may mean that the sun has moved out of the region where it formed, or that some
of the oxygen has been captured by dust in interstellar space.
These direct, physical measurements of the universe right on the sun's
doorstep help us understand the history and future of our solar system
and the galaxy. What scientists learn can help protect
human spaceflight and teach us more about our home in the Milky Way.
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