Our solar system is making its way through the vast and inhospitable regions of the Milky Way. It is filled with gases ten times thinner than the interstellar medium. The Sun's path through the Milky Way has now brought the solar system into the center of the region. Its width is currently estimated at 1,000 light-years, but it is slowly growing and expanding at a rate of more than 6 km/s.
Space Tunnel
The gas in this region is not only thin (1/10th of the average density of the interstellar medium, or 0.5 atoms per cubic centimeter), but also very hot, just below 1 million degrees Celsius. It stretches 300 light-years within the spiral arm of the Milky Way constellation Orion and is known as the local bubble. The solar system has passed through it for at least 5 million years in the past, up to 10 million years according to some estimates.
The gas density now is 0.1 atoms per cubic centimeter. There are others that are adjacent to our local bubbles; They are connected to each other by tunnels. For example, bubble I is 500 light-years from the sun. There are also Bubble II and Bubble III. However, scientists do not rule out that there may be more.
For decades, scientists have suspected the existence of this giant bubble that travels across the Milky Way. But only recently has this been confirmed. Last year, an accurate map of the region and a computer model of the evolution of the local bubble were compiled. In conclusion, this made it possible to confirm one of the hypotheses of its appearance.
Cold shell
The Gaia Astrometry Space Telescope tracks the precise movements and positions of stars and is considered to have produced the most accurate map of the Milky Way's periphery. The data he collected showed that all seven star-forming regions and young stars adjacent to us were located on the surface of the local bubble.
This confirms the hypothesis that it was formed as a result of the death of a supernova. After all, it is only in this process that the outer area is the most compacted due to the action of the shock wave. The cloud of gas and dust is pushed out and gathers into a thick, cold empty shell. Nova is born in it because there is plenty of fuel.
The researchers went one step further and created computer models of gas clouds and star motion and rewind them to the past. It was later discovered that local bubbles began to exist 14.4 million years ago as a result of the explosion of 15 supernovae. They erupted continuously for millions of years. The last supernova died about 2 million years ago.
Look for bubbles
At first, the bubble expanded at a rate of about 100 km/s, now it is much smaller - 6.7 km/s. Interestingly, nothing happened inside the bubble, and scientists understand why we are in a almost empty part of the Milky Way. This may be because the solar system is much older than the native bubbles. In general, when the first supernova exploded to produce it, the Sun was far away from the region and was the closest to enter the region by cosmic standards.
There are still two star clusters with supernovae in the local bubble. Their age is estimated to be 15-16 million years. They are located at the edge of the shell. In the future, scientists hope to find more of these bubbles in order to better understand them.
This will answer the question of how these bubbles can become stellar nurseries that interact with each other. And how galaxies like the Milky Way evolved.
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