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Formation d’étoiles, étoiles, galaxie, supernovæ

Local bubble in the origin of stars in the vicinity of the galaxy

The Milky Way, with nearly 200 billion stars, is rich in gas. Far from being evenly distributed, the latter accumulates in certain areas and neglects others. This is the case of the Sun’s neighborhood that forms the “local bubble,” a cavity surrounded by an envelope of neutral gas and dust, and filled with hot and not very dense plasma as Lucky Puspitarini and Rosine Lallement, of the Paris Observatory, and their colleagues observed in 2014. For the first time, using data From the Gaia Space Telescope, Kathryn Zucker, of the Harvard and Smithsonian Center for Astrophysics (CfA), and colleagues traced the history of this region. calendar ? Most stellar nurseries (the clouds of gas that generate young stars), located 650 light-years from the Sun, may have formed after the creation and expansion of the Local Bubble, 14 years ago. million years ago.

The existence of the local bubble has already been known to scientists since the end of the 1970s. The gas surrounding one or more supernovae (a violent explosion marking the end of life for massive stars) whose masses and trajectories were calculated by Dieter Brechwerdt, of the Berlin Institute of Technology, and colleagues, could have exploded in 2016. Stars born within The same cloud with similar masses ends in a time window of only a few million years. However, astronomers have not yet succeeded in reconstructing the exact shape and stretching of the local bubble.

The Gaia satellite, by producing a highly accurate catalog of the position and movement of the stars near the Sun, has opened the possibility to learn more about the history of the local bubble. Katherine Zucker and her colleagues mapped this region in three dimensions, including the location of seven molecular clouds where new stars are forming. The researchers showed that these clouds are present on the surface of the local bubble.

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According to the researchers’ model, the sequential explosion of about fifteen supernovae, which began 14 million years ago, will be the source of this plasma bubble. The progenitor stars of the supernova are likely in the star-rich association of Scorpius and Centaurus, which are now about 400 light-years from the Sun.

Far from repairing, the bubble will continue to grow at a speed of about 6 kilometers per second. The resulting shock wave will accumulate at the bubble edges for gas and dust, conditions that lead to star formation.

If the solar system is currently at the center of the bubble, that’s just the result of chance. 14 million years ago, the Sun was a far cry from the first star to explode in a supernova. It would have entered the bubble nearly 5 million years ago and would continue on its own course. When bubbles are assumed to be rare, the probability of being in the center of such a bubble is extremely low. This logic suggests that galactic gas, on the contrary, will be dotted with a large number of such bubbles. A result that raises many questions: Do bubbles collide? How do they react? How do they cause stars to be born? Is it possible to appoint them? etc.