Telescope spots galaxy refueling in the early universe

first_img Email Sign up for our daily newsletter Get more great content like this delivered right to you! Country As a result, the early generations of stars were rich in hydrogen. Burning this fuel made them grow large and burn hot and fast. They emitted intense radiation, which heated up all the gas in the galaxy, making it unable to cool and coalesce into new stars. When these supercharged early stars ran out of fuel and exploded as supernovae, they would have blasted the interstellar gas right out of the galaxy.This prediction poses a problem for astrophysicists: If the early generation of stars was ridding galaxies of cool gas, galaxies would soon die, unable to create any new stars and evolve any further. Theorists think that sustainable galaxies must draw in fresh cool gas from surrounding space. But astronomers couldn’t check the galaxies of that primordial era, before the universe was 1 billion years old, because they appear to us as specks of light.Enter ALMA. Its dishes collect wavelengths about a millimeter or less—much shorter than those detected by traditional radio telescopes. Such signals are produced not by brilliant stars but by cooler objects such as gas. ALMA, sited high up in the mountains of northern Chile and still under construction, is also orders of magnitude sharper and more sensitive than similar telescopes because it is made up of many separate dishes—66 when completed—all working together as one giant instrument. Maiolino’s team used 30 of ALMA’s dishes to look for the faint glow of ionized carbon—a marker for the sort of cool gas from which stars form.Focusing on a galaxy called BDF3299, just 800 million years after the big bang, the team reports online this month in the Monthly Notices of the Royal Astronomical Society that it could see some carbon in its center and a large clump of carbon gas just to one side. That clump of gas didn’t have any stars associated with it, so the researchers concluded that it was cool fresh fuel either orbiting BDF3299 or in the process of falling into it. “Accretion of cool molecular gas is thought to be a key mechanism in galaxy evolution. This is the first time it has been seen at work in such a primordial system,” Maiolino says.Other experts concur. “We know refueling has to go on in the early universe to get to the galaxies we see today. This is a nice first glimpse of that,” says astronomer Timothy Davis of the University of Hertfordshire in the United Kingdom, who was not involved in the study. “Without the sensitivity of ALMA it would be impossible to see this sort of detail. It’s pretty vital.”The team has just received new data from ALMA with higher quality and greater resolution, so over the next few weeks they hope to tease out more details of the infalling gas. “We’ll be able to pin down details of the accretion process,” Maiolino says. Astronomers using a powerful radio telescope in Chile have observed cold molecular gas falling in toward the center of a galaxy—and so fueling star formation—back at a time when the universe was just a few hundred million years old. The find—made by the Atacama Large Millimeter/submillimeter Array (ALMA)—could help astronomers understand how early galaxies grew into the ones we observe today.“The models predicted just what we saw, which is something really exciting,” says team leader Roberto Maiolino of the University of Cambridge in the United Kingdom. “That means we are going in the right direction on understanding how galaxies formed.”Galaxies and stars in the early universe are thought to have been very different from those we see around us now. Most of their ingredients were simple hydrogen and helium from the big bang. Other, heavier elements were rare in that early epoch, as most were only later forged in the furnaces of stars that had to die and explode for those elements to get mixed in with the hydrogen.center_img Click to view the privacy policy. 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