The “local bubble”. This is what astronomers call a kind of shell of around 1,000 light years that surrounds our solar system. It is thought to have been formed by multiple explosions of massive stars in supernovae. A few million years ago. And since its surface concentrates gas, gas and dust, stars are born there. Astronomers recently managed to map it (see article below). Today researchers from the Center for Astrophysics at Harvard University (USA) unveil a new 3D image. That of its magnetic fieldmagnetic field.
Note that the Milky Way looks a bit like a piece of Emmental. With many cosmic superbubbles similar to our local bubble. Learning more about the local bubble should therefore allow astronomers to better understand the evolution and dynamics of these superbubbles. But also their influence on the birth of stars and more generally on the shape of large galaxies.
Better understand the role of magnetic fields
Convinced that magnetic fields play an important role in many astrophysical phenomena, the researchers combined data from multiple space missions (GaiaGaia and Planck-Planck) to observe the polarization of light near our solar system. A polarization created by magnetically aligned dust particles. And which reveals the orientation of the magnetic field acting on it.
From the 2D map they obtained, the researchers switched to 3D, assuming that most of the interstellar dust producing the observed polarization resides on the surface of the Local Bubble and that the theories predict that the magnetic field would be “carried” into the surface of the bubble it’s extended are correct. “As technology and our understanding of physics improve, we can improve the accuracy of our map and hopefully confirm what we’re seeing,” says Alyssa Goodman, an astronomer at Harvard University, in a press release. But already, astronomers can begin to study the influences of magnetic fields on star formation in superbubbles and better understand how these fields influence many other cosmic phenomena.
We are passing through a huge bubble of gas with stars forming on its surface
Our solar system is navigating a particularly empty region of space. Surrounded by what astronomers call a local bubble. And today they tell us how this bubble was formed. After the explosion of several supernovae.
Article by Nathalie MayerNathalie Mayer published on 01/16/2022
Astronomers have known for decades that it exists around our solar system like a gigantic bubble. A “local bubble” that’s still about 1,000 light-years across. Today, researchers from Harvard University and the Space Telescope Science Institute (STScI) report that they have discovered that all of the youngest stars around us are located right on the surface of this bubble. All younger stars, but also several known star-forming regions and some molecular clouds – these are dense areas where stars can form successfully. Based on these observations, these astronomers tell us the story of this strange bubble.
Did you know ?
The existence of our local bubble was revealed in the 1970s and 1980s by optical, radio wave, and X-ray observations, which showed that our little corner of the Milky Way is about 10 times thinner than average.
It all started almost 14.5 million years ago. With a fairly intense star formation phase. Then with the supernova explosion of fifteen massive stars. A series of explosions that began pushing out interstellar gas and dust. Let’s stay in a sparse region. And further, a bubble-like structure is formed, the surface of which has exactly the right properties for star formation.
According to astronomers, this local bubble is still expanding today. At a speedspeed of almost 6.5 kilometers per second. That’s about 23,400 kilometers per hour. A high speed in our magnitude. But speaking of an astronomical phenomenon, researchers believe our local bubble “has lost its clout.” And practically reached a plateau.
Other bubbles in the Milky Way?
To rewrite the history of this amazing bubble, astronomers have relied on numerous tools. Models of supernova-supernova, stellar motion – particularly according to data from the European space mission Gaïa – or even 3D maps of the matter that precisely surrounds our local bubble.
The researchers point out that it is fortunate that our Sun is almost at the center of this bubble today. The result of his journey through the Milky Way. He led it there about 5 million years ago. According to astronomers, evidence that this type of structure must also exist elsewhere in our galaxy. Because if these giant bubbles were rare, it would be statistically unlikely that we would find ourselves at the heart of any of them.
So our Milky WayMilky Way would look a bit like cheese with holes. Holes – the bubbles – dug by dying stars, supernovae, and at the edges of which you can see forming stars. Now researchers just need to map some of these bubbles. To determine their shape, size and location. And why not, their ways of interacting. A new way to understand the role of end-of-life stars in star formation, but also in the evolution of galaxies.
Who created the local bubble, where is the sun? supernovae…
In the 1970s, it was highlighted that the local bubble in which our Sun and its planets currently orbit would have been formed by the sequential explosion of multiple supernovae, a cosmic fireworks display that occurred about 10 million years ago. However, another interpretation is possible: solar wind exchanges charge with the neutral gases of the interstellar medium. In order to decide between them, a research team has developed a special instrument. Result: The supernova hypothesis is strengthened.
Article by Xavier DemeersmanXavier Demeersman published on 09/09/2014
As we recently mentioned, according to a study that made the cover of Nature, our galaxy, the Milky Way, in which we live belongs to a galactic supercontinentsupercontinent created by its discoverers Laniakea (“immeasurable celestial horizons” in Hawaiian). was called. So much for the very large format painting. On a more modest scale, our Sun is currently evolving in one of the lobes of what astrophysicists have called the “local bubble” since its discovery in the 1970s and 1980s.
Estimated to be 300 light-years long, its shape resembles that of a peanut or an hourglass. Its density is very low (0.001 atoms per cubic centimeter) and the temperature of the gases is particularly high in all directions, as first X-ray observations show.
Abundance of supernovae
To explain these voids in the interstellar medium, a series of supernovae is proposed as the main scenario. Remember that these explosions of stars of incredible power (the energy involved can exceed the energy developed by the Sun for a few million years) are not uncommon in the Milky Way. Astronomers estimate that our galaxy has one every fifty years on average. If many escape us (the 1604 Kepler supernova was the last observed in our galaxy), it is largely because they are obscured by star clouds and dust from the galactic disk.
However, things were very different in our neighborhood 10 million years ago. In fact, it appears that several members of a massive star cluster literally burst out like popcorn, leaving huge residual bubbles that are still expanding today! This must have happened at a reasonable distance from Earth, since our biospherebiosphere does not appear to have suffered shockwaves and bears no stigmata for that period of time.
Supernovae seem to have created the bubble
The hypothesis of a local bubble dug by the explosion of stars is not unanimous in the scientific community. F. Scott Porter, one of the authors of the article published this summer in Nature (July 27, 2014 issue), recalls: “For the past decade, researchers have questioned the interpretation of supernovae, suggesting that most, if not all, of this soft X-ray radiation is the result of charge exchange”. A fee swap? To them, these are waves of electrically charged particles emitted by our star (the solar wind) on neutral gas beaches because the glow observed in the X-ray field produces the same effect as ancient supernova remnants.
To decide between the two proposals and shed light on this issue, the researcher teamed up with Massimiliano Galeazzi (University of Miami) and his team to develop a detector sensitive and capable of this wavelength to distinguish the two signatures. Launched on December 12, 2012 at an altitude of about 275 km, her baby, named DXL (Diffuse X-ray Emission from the Local Galaxy), spent just five minutes in space before returning to Earth with valuable data on the charge exchange in the solar system. Finally, after several months of research, it appears that about 40% is of solar origin. So ancient supernovae would be responsible for everything else.
“This is an important discovery,” concludes Professor Galeazzi, as it “touches our understanding of the region near the Sun and can therefore serve as a basis for future models of the structure of our galaxy.” Together with new measuring devices, DXL is scheduled to make the next jump into space in December 2015.