Stars have to form from something. But some galaxies are making more stars than they should be able to, given their reserves of star-forming gas. So where is the celestial star-fuel hiding? Apparently it’s intergalactic. Here’s more from Phys.org:

Previous research in the field of star formation suggested that some galaxies are producing more stars than what their reserve of star-forming gas would allow…. “Observations of galaxies are similar to looking through an airplane window at night and seeing bright city lights surrounded by darkness. Finding this fuel source is like discovering that in the darkness lies the farms and supply routes that support the populations in the cities,” explains [Arizona State University astronomer Sanchayeeta Borthakur]

To determine where the gas might be originating, Borthakur used a statistical method known as cross-correlation (to measure the association between two quantities), and data from two publicly available astronomy catalogues…. With those data, she was able to quantify how gas-rich galaxies are associated with clouds seen in the intergalactic medium.

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