The Universe Tonight
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Astrophysics with the Eyeball
By Josh Walawender, Post Doc for the Institute for Astronomy at Hilo
Our home galaxy, the Milky Way, can be seen streaming across the sky in the early evening in winter and summer from here in Hawaii. This "river of stars", made up of billions of distant suns, is marred by dark patches where the light of those distant stars is blocked by clouds of interstellar dust. This dust is the raw material of star birth. In the densest clumps within these interstellar clouds, hundreds or even thousands of stars of different sizes and colors are born in these stellar nurseries. Although the process of stellar birth takes millions of years, we can look up at the night sky and see many of these regions at various "ages" and piece together the story of the early life of a star. As these stars age and grow, they will destroy their parent cloud through stellar winds, radiation, and supernovae. At this stage, they are sometimes visible as spectacular emission nebulae such as the Great Nebula in Orion which will be prominent in Hawaii's sky that night.
As groups of young stars evolve, they will emerge from their parent cloud and be visible as a scattering of jewel-like stars cast against the backdrop of a black sky. These "open clusters" still represent very young stars. As they age, the stars will slowly drift apart to become part of the general population of stars in the galaxy, the ones visible when you look up at night. Our Sun was once part of one of these stellar nurseries, and later, part of a cluster of stars. Now, roughly 5 billion years later, it's stellar siblings have all drifted away, but we can watch as other stars are born and evolve and understand our own star's origin.
Josh Walawender studied astrophysics at UC Berkeley and received his PhD from the University of Colorado. He now works for the Institute for Astronomy in Hilo and studies star formation and evolution.