Scientists take bite of 'alien' space cloud that encompasses us
Our solar system is adrift in an "alien" cloud, recent headlines have trumpeted. But that news is actually tens of thousands of years old. What's new is that NASA has, at long last, tapped into this interstellar wonder.
NASA's IBEX spacecraft (IBEX stands for Interstellar Boundary Explorer) is about the size of a bus tire, but it's performed a mighty task.
For the first time, IBEX has directly measured chemical elements of an "'alien' cloud that has blown into the solar system," said Eric Christian, an IBEX mission scientist at NASA. The agency reported its findings in a series of papers this week.
This so-called Local Cloud is a longtime visitor. It arrived, scientists believe, thousands upon thousands of years ago from a group of super-giant stars "found by looking back in the direction of the cloud's movement," Christian said Wednesday in an interview with the Los Angeles Times.
"The space between stars is mostly empty, but there is gas there," Christian said.
"The denser parts of interstellar space are called clouds," he added. There are several clouds near our solar system, he said; we're at the edge of the Local Cloud.
But solar wind and the solar magnetic field effectively blew "a bubble" in this cloud -- a bubble in which we live -- so "almost everything we've measured before comes from the sun or the solar system."
Now we've bitten into that alien space cloud.
What NASA found by collecting gases directly from the cloud was "the same chemical elements ... found on Earth and in the sun and solar system, but the amount of each element [specifically the oxygen to neon ratio] was different than that in the solar system and different than the galaxy as a whole," Christian said.
But why is there less oxygen in the Local Cloud? Perhaps the oxygen has been caught by small particles of dust between the stars, maybe as water ice, he speculated. Or perhaps the super-giant stars from which the cloud appears to have originated are somehow different.
Understanding the Local Cloud will help us better understand that previously mentioned solar bubble -- our heliosphere -- which acts as a shield against harmful cosmic rays, Christian said, and may have affected the development of life on Earth.
"We need to understand the size and shape of this shield," which is affected by the speed of the inflowing interstellar wind, Christian said. IBEX, by the way, also measured this wind and showed that it was not as strong as previously thought.
"As we look for nearby solar systems," he added, "understanding our shield helps us understand the 'astrospheres' around other stars and whether it affects the habitability of planets in those nearby solar systems."
IBEX's measurements set the stage for more interstellar excitement.
In the next couple of years, Voyager 1 will pass out of the heliosphere, Christian said, "and become our first interstellar probe."
-- Amy Hubbard
Image: Artist's rendering of IBEX. Credit: NASA