Space is a pretty empty place. But it’s not completely empty, as a new map of the interstellar space surrounding the 1,000 light-years around the sun shows.
Using the light from 1,857 stars, a team of French and American astronomers were able to measure the density of the gas surrounding us by examining fine differences in the starlight. They confirmed the presence of the Local Cavity, represented by the white area above, which scientists think was swept of gas by an old supernova explosion.
“Nobody knows for sure, but the consensus of opinion is that there was a giant supernova that went off about five or ten million years ago and the big explosion cleared everything out of the way and left a big hole in the interstellar medium,” said astronomer Barry Welsh at the University of California Berkeley.
The Local Cavity has radius about 260 light-years. The area is so empty that if you were to fly along scooping up the hydrogen atoms in the interstellar medium between our solar system and the edge of the cavity, you’d only have collected enough to fill half a coffee cup with them, Welsh said.
The Local Cavity is surrounded by a wall of relatively denser gas. But the wall isn’t impenetrable. It’s riddled with “interstellar tunnels” that lead from one pocket of less dense gas to another.
The work builds on a 2003 map and was published in the journal Astronomy and Astrophysics. It incorporates more than twice the data as the previous map. By mapping this gas, Welsh said we were filling in major blanks in our knowledge about the galaxy.
He said that our previous maps of our local area just had the stars, but not the gas, which was like “a map of the USA that just has the cities.”
