It has the potential to fully transform our view of the Galaxy." The future is bright for chemical cartography "This illustrates the value of chemical cartography in identifying the Milky Way's structure and formation. "A big takeaway is that the spiral arms are indeed richer in metals," Hawkins explained. And, because he used metalicity to chart the spiral arms, hitherto unseen regions of the Milky Way's spiral arms showed up in Hawkins' map. Taking the resultant map, the researcher compared it to others of the same area of the Milky Way created by different techniques, finding that the positions of the spiral arms lined up. In cosmic terms, that represents our stellar neighborhood's immediate vicinity. To confirm this theory, as well as create his overall map of metalicity, Hawkins first looked at our solar system's galactic backyard, which include stars about 32,000 light years from the sun. Conversely, spaces between the arms should be marked by metal-poor stars. If the Milky Way's spiral arms trigger star births as predicted, then they should be marked by young stars, aka metal-rich stars. Thus, young stars are expected to be "metal-rich" or hold a "high metalicity." This stellar cycle of life and death has continued throughout the 13.8 billion-year history of the universe, with every subsequent generation of stars being more metal-rich than the last. Therefore, when metal-enriched clouds of dust and gas collapse to birth stars, this next generation of stars is richer in metals than the last. That means the oldest stars are also composed of mostly hydrogen and helium and are thus "low metalicity" or "metal-poor."ĭuring their lives, these older stars forge heavier elements via nuclear fusion - but when they run out of such fuel, are ripped apart by supernova explosions that spread the metals throughout their cosmic environment. This so-called metalicity serves as an age measurement because the early cosmos was filled with hydrogen and helium, but little in the way of metals. One way of working around this dust veil is by observing exactly how metal-rich the stars that lurk in hidden regions are. That means some regions of the Milky Way’s spiral arms go unobserved. Though young stars can be detected by tracking the bright blue light they emit, observations of this kind can be obscured by thick clouds of dust which present a challenge to even the most advanced telescopes. In other words, identifying an overabundance of young stars implies the location of a spiral arm. As this rotation occurs, it compresses gas and dust to ultimately trigger star births. One traditional way of mapping the Milky Way involves monitoring the concentrations of young stars that are created as the galaxy's very dense spiral arms rotate. The Milky Way galaxy may be a different shape than we thought New Milky Way map reveals the magnificent messiness of our galaxy Gaia spacecraft: Mapping the Milky Way like never before This hasn't prevented scientists from modeling intricate models of the shape of the Milky Way, but Hawkins wanted to verify the accuracy of those models while simultaneously investigating whether chemical cartography can offer an even better view of the Milky Way's arms in general. "You can look around at the buildings and you can see what street you’re on, but it’s hard to know what the whole city looks like unless you’re in a plane flying above it." "It's like being in a big city," Hawkins explained. We simply can't get far enough to observe our galaxy from an outsider's perspective. We're basically analyzing it from the inside, with Earth sitting in the Orion Arm around two-thirds of the way from the central bulge. The difficulty in assessing the Milky Way's morphology comes from the fact that we live in it. However, the exact shape of this striking structure - down to the number of arms our galaxy has - remains uncertain. Finding where the Milky Way's hot young stars hang outįor at least seven decades, astronomers have understood that our galaxy has spiral arms that extend out from the dense concentration of stars, gas, and dust which lie at its heart, known as the "central bulge." "Those maps are revealing things we thought to be true but still need to check."Ĭhemical cartography isn't really a new process, but only recently did scientists manage to develop telescopes with enough observing power to get significant results using the technique. "Much like the early explorers, who created better and better maps of our world, we are now creating better and better maps of the Milky Way," Hawkins said.
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