Astronomers Spot Galactic Wind From Early Universe
The ejection of molecular gas from a galaxy 12 billion light-years away may have kept an early galaxy from burning out too quickly
Researchers have detected a cosmic wind in a galaxy 12 billion light-years away, the first time the phenomenon has been observed at such a distance and so long ago in the universe's past. But a galactic wind isn’t anything like sea breezes on Earth. It’s believed to be a regulatory mechanism that helps determine how quickly a galaxy creates stars, reports Rafi Letzter at LiveScience. This latest look at a galactic wind from the early universe can help astrophysicists understand why galaxies evolve like they do.
In general, there are several roads galaxies can go down when they form. In one scenario, they live fast and die young. For reasons that are not well understood, some galaxies begin to churn out massive stars using the gravity and gasses available to them, producing stars 1,000 times faster than other galaxies, which has earned them the name “starburst galaxies.” The massive stars they produce don’t last long, eventually exploding into supernovae that are powerful enough to overcome the force of gravity and fling gasses and other materials into space. Over time, that loss of matter leads to the end of the galaxy. One such fast-burning galaxy was just revealed last week, a monster starburst galaxy called COSMOS-AzTEC-1 that will likely burn itself out after just 100 million years.
But not all starburst galaxies go down in a blaze of glory. Instead, some are believed to slow down their furious pace of star formation by ejecting some of their molecular gasses into a halo around the galaxy via galactic wind. According to a press release, that star-fuel either drifts away into space or rains back down into the galaxy at a later date, setting off more rounds of star formation. In essence, the wind slows down the furious pace of star formation creating a self-regulating mechanism that keeps the galaxy from burning out so quickly.
That galactic wind is what astronomers observed in the new study published in the journal Science. Using the Atacama Large Millimeter/submillimeter Array (ALMA) based in Chile, researchers detected the gas outflow from a galaxy called SPT2319-55, which was churning out stars when the universe was just 1 billion years old.
While astronomers have seen similar winds in other galaxies, this is by far the oldest instance of cosmic wind recorded, which will help researchers understand the earliest eons of galaxy formation.
“Galaxies are complicated, messy beasts, and we think outflows and winds are critical pieces to how they form and evolve, regulating their ability to grow,” says astronomer Justin Spilker of the University of Texas at Austin, the study’s lead author, in a statement.
Finding the wind was no easy feat. The signals from these galaxies in the distant past are faint and often obscured by other information raining down on us from the sky.
To amplify the signal, the astronomers used a technique known as gravitational lensing. In this technique, astronomers look for a massive celestial body—like a large galaxy or black hole—between the telescope and the object they hope to see to get a better view of a super-distance object to get a better view of a super-distance object. If it’s in the right position, the gravity of the massive foreground object warps light around it, amplifying the light behind it and creating multiple images of the target object.
In this case, the astronomers used a large galaxy within the line of sight of SPT2319-55, which brought ancient galaxy into focus. Using a computer program, they were unable to unscramble and combine the images created by the gravitational lens.
Amber Jorgenson at Astronomy reports that ALMA detected bursts of galactic wind shooting out from the galaxy at 500 miles per second. They also found the chemical signatures of hydroxyl in the wind, a prominent component in star-forming regions, meaning the wind was venting star-fuel into space.
The next question is whether these types of winds were common in early galaxies or if SPT2319-55 is a special case.
“So far, we have only observed one galaxy at such a remarkable cosmic distance, but we'd like to know if winds like these are also present in other galaxies to see just how common they are,” Spilker says in the press release. “If they occur in basically every galaxy, we know that molecular winds are both ubiquitous and also a really common way for galaxies to self-regulate their growth.”
Letzter at LiveScience reports that researchers aren't certain whether the galactic wind will allow SPT2319-55 to live a long, fulfilling cosmic life. It’s possible that the wind is not strong enough to slow down runaway star formation, meaning the galaxy might die young anyway. It’s also possible that there is so much dark matter around the galaxy that it will trap any gasses expelled by the galactic wind, preventing the gasses from falling back into the galaxy and eventually starving it of star fuel and leading to its extinction.
Whatever happens, it’s likely all that galactic wind won’t go to waste. Another recent study shows that half of our own Milky Way galaxy is made of material ejected by galactic winds in other galaxies, suggesting that even if SPT2319-55 burned out long ago, part of it probably still lives on somewhere.