Scientists Map A Giant Bubble 1,000 Light-Years Old That Surrounds Earth
Our planet is surrounded by a "giant bubble" 1,000 light-years across. Now, astronomers have made the first 3D map of its magnetic field.
The giant structure, known as the Local Bubble, is a hollow bubble of hot, diffuse plasma surrounded by an outpouring of cold gas and dust that forms its surface stars. It's just one of the many hollows in the Milky Way - what makes our galaxy look like an enormous slice of Swiss cheese.
Great bubbles are shock waves caused by the death of many massive stars that explode at their ends in massive supernovae that spew out the gas and dust needed to give birth to new stars. Over time, other stars, like our own, wander into the cavities left by these explosions.
Although there are some ideas about the formation of superbubbles, astronomers are still not sure how these giant bubbles evolve by interacting with our galaxy's magnetic field, and how this affects the formation of stars and galaxies.
To find out more, a team of astronomers, working on a summer research program at the Harvard-Smithsonian Center for Astrophysics, mapped the local bubble's magnetic field.
Theo O'Neill, who was at the time an undergraduate student in astronomy, physics and statistics from the University of Virginia, said: "Space is full of these wonderful bubbles that lead to the formation of new stars and planets and affect the general shapes of galaxies.
By learning more about the exact mechanisms that drive the Local Bubble, which the Sun lives in today, we can learn more about the evolution and dynamics of superbubbles in general.”
The Milky Way, like many other galaxies, is filled with a magnetic field that gently draws stars, dust and gas into mind-boggling structures like giant, bone-like filaments. Arguably, astronomers aren't sure what gives rise to the galaxy's magnetic fields.
"From a fundamental physics standpoint, we've known for a long time that magnetic fields must play important roles in many astrophysical phenomena," Harvard astronomer Alyssa Goodman, who was one of the mentors for the research program, said in the statement.
But studying these magnetic fields has been very difficult. Computer simulations and surveys of the skies today may be good enough to start integrating magnetic fields into our broader picture of how the universe works, from the motions of tiny dust grains onwards to the dynamics of galaxy clusters.”
To map the magnetic field, the astronomers used previous information from the European Space Agency's (ESA) Gaia space telescope, which inferred the approximate boundaries of the Local Bubble from concentrations of distant cosmic dust.
However, the researchers turned to data from another ESA space telescope, Planck, which showed faint emissions of polarized light from the dust.
Because the polarization, or direction of vibration, of the light is a major endowment to the magnetic field acting on the dust, astronomers have used it to stitch data points together into the vast three-dimensional tapestry of the superbubble's surface.
To make their map, the researchers note, they made some big assumptions that they would need to test — in particular that polarized dust is located on the surface of the bubble — but, once fine-tuned, they believe it could become an invaluable tool for studying star formation across the galactic backyard.
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