The Solar System hovers in the middle of an empty region of space called the Local Bubble. No new stars have been born in this region in the past 14 million years, only in space with denser matter blocked at the edge of the bubble. Stars remained in the region before the bubble formed, as did the Sun.
The existence of the local bubble has been known since the 1970s. A recent study by the Harvard and Smithsonian Center for Astrophysics (CfA) in Nature revealed how fast it is expanding and what’s causing it.
After the previous movements of young stars nearby, we have reconstructed the history of our galactic environment
said Catherine Zucker, a Hubble fellow at NASA.
Supernova explosions generated an ever-expanding shock wave, forming a dense envelope of interstellar gas and dust on the surface of a local bubble.
The researchers created a 3-D map of the star-forming regions at the bubble’s edge and their motion, based on data from the European Space Agency’s Gaia space observatory. Based on this, it was found that the shock wave considered as a projectile is currently spreading at a speed of 6.4 kilometers per second.
Photo: Leah Hustak / STScI
The multi-bubble shape of the empty region was created by more than a dozen starbursts.
We were able to calculate how much kinetic energy the expanding surface of the local bubble currently has and compare the amount of energy that would be required from a supernova. Based on that, 15 supernovae were needed for the current projectile
Zucker said. Stellar explosions have occurred in two different groups over the past millions of years.
The Earth is currently in the middle of the bubble, but that’s a coincidence. Our star system was about 1,000 light-years away when the bubble began to form and we only entered this region 5 million years ago.
The observations support the hypothesis that the main driving force for star formation is condensation at the intersection of the shock waves of starbursts. So the local bubble is not unique, in fact, the Milky Way is a lot like cheese with holes.
Otherwise, the solar system would have left the bubble 8 million years from now, but it looks like it hasn’t been around for a long time. The shock wave spreads and disappears once it reaches its maximum limit. This process ends now and the bubble walls will soon slow down to the point that they will dissolve into the surrounding gas clouds.
(Cover Image: NASA/ESA/Getty Images)
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