In 1994, when the Northridge earthquake knocked out power (and therefore light) to Los Angeles, emergency centers received calls from concerned citizens who reported a “giant silvery cloud” hovering over the city.
Sadly, the increase in light pollution over the past century has turned the Milky Way from a common sight into one that many folks have never seen.
The Milky Way used to be visible on every clear, moonless night, everywhere in the world. Credit: Bill Saxton NRAO, AUI, NSF Robert Hurt NASA. Image showing where Earth resides within the Barred Spiral Milky Way. Within this huge spiral structure, Earth and the Sun and its planets are located in one of the spiral arms of the Milky Way (called the Orion Arm) which lies about two-thirds of the way out from the center of the Galaxy (and one third from the center of the galaxy). Imagine a disk with spiral arms reaching out from the center. The current hypothesis is that the bar structure acts as a type of stellar nursery, fueling star birth at their centers. While the Milky Way appears as an arch to our eyes, it is actually a spiral galaxy-a sprawling pinwheel of starlight and dust containing 100 to 400 billion stars! Specifically, it’s a “barred spiral galaxy” because it has a central bar bar-shaped structure composed of stars. Added together, these myriad stars produced the soft glow that we see as the Milky Way. It glows with the combined light of billions upon billions of faraway stars, each too faint for our eyes to resolve. Night Sky Map for December 2023: Rotation of the Starsįrom our vantage point within the galaxy, the Milky Way appears as a huge, shimmering cloud of light arching from the southern horizon to high overhead.
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