Nearby galaxy gives window into early universe

first_imgA nearby dwarf galaxy is giving astronomers a unique view of what the first stars and galaxies in the universe may have looked like. The early universe was made up almost exclusively of the hydrogen and helium created shortly after the big bang. All the other stuff we have today was made by stars burning hydrogen and helium as fuel, fusing them into heavier elements, and then spewing them out when they explode as supernovae at the end of their lives. Models suggest that the first generation of stars, made almost exclusively of hydrogen and helium, were unlike anything we see today—huge monsters hundreds of times the mass of the sun pumping out intense high-energy radiation. Such stars are thought to have played a role in the epoch of reionization—a period before the universe was 1 billion years old during which all the gas it contained was stripped of electrons, becoming ionized—but they are too far away to be studied. Now, a team of astronomers has surveyed a dwarf galaxy called IZw 18 (pictured above), which has the least heavy elements of any galaxy in the nearby universe. They found a large region of the galaxy giving off a signal of helium being ionized. It takes intense radiation to knock electrons from helium, so the team suggests this month in The Astrophysical Journal Letters that IZw 18 may be the home of modern-day equivalents of those primordial, bright, supergiant stars. Studying them more closely could teach us more about conditions during the epoch of reionization.last_img

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