Star Formation Might Depend on Galactic Magnetic Fields

The Hubble captured this image of Arp 220, the aftermath of a galactic merger about 250 million light-years away. It's the brightest of the three galactic mergers closest to Earth. Astronomers studied Arp 220 with the Submillimeter Array (SMA) to determine the role magnetic fields play in the formation of stars. Image Credit: NASA/ESA/STScI/HST

A galactic merger is a chaotic event. When two massive structures like galaxies merge, their powerful gravitational forces wrench stars out of their usual orbits in a process called violent relaxation. In essence, the merging galaxies are evolving rapidly, and small perturbations can be amplified as the system moves toward a more stationary state.

Intuition suggests that this chaos should disrupt the galaxy, including its star formation, but new observations of the Arp 220 galaxy merger show that something else happens: the merger creates a massive magnetic field that traps gas and encourages more stars to form.

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