Death is a part of, well, life, and is something that happens on small and big scales alike. In fact, the Hubble Space Telescope just detected six dead galaxies from the early universe. However, scientists are baffled as to why the massive galaxies died when they did, given all the fuel near them.
Together with the Atacama Large Millimeter/Submillimeter Array (ALMA), Hubble detected the galaxies (which are believed to have formed approximately three billion years after the Big Bang). Researchers were shocked to discover that the galaxies were unusually dead, and had run out of the elements needed for star formation—namely, cold hydrogen. Lead researcher Kate Whitaker notes that this was the peak period in our universe’s history for star formation, so a fuel source shouldn’t have been an issue. The real question is why did these galaxies live so fast and die so young?
The galaxies were tricky to find, and scientists were only able to do so thanks to strong gravitational lensing—that is, using galactic clusters to magnify and bend light emitted from the early universe. ALMA identified cold dust (an alternate for the hydrogen) and Hubble located the exact region where the stars had originally formed, which led them to be able to show where the galaxies would have formed if there had been more of those vital ingredients.
Those six galaxies were each able to continue expanding since then, but not by normal means, aka by star creation. Instead, they slowly merged with other smaller galaxies (and their contents, like gas); further formation and development beyond that point were extremely limited.
While scientists are thrilled about Hubble’s discovery here, they’re also left wondering about why the galaxies died so rapidly. Mostly, they want to know why—was it rapidly consumed? Did something else siphon the fuel source? It’ll take scientists a while to find the answers here, but in the meantime, we can still be in awe at Hubble’s capabilities decades after it first launched.