The Sun is a star that provides Earth with the energy that drives most of our diverse and amazing biology. But where and how do stars form? We can see places where stars are forming right now in our late winter sky. The Great Nebula in Orion is one of these places, and it’s sometimes called a “stellar nursery.” The Orion Nebula is visible to eyes unaided within “Orion’s sword”, just south and east of Orion’s “belt stars.” Binoculars and telescopes provide even better views. Nebula is the Latin term for “cloud”, and indeed the Orion Nebula and thousands of similar nebulae within our Milky Way Galaxy are interstellar clouds. Interstellar clouds are the more concentrated parts of the interstellar medium, the highly dispersed gases and dust particles that exist between stars. These clouds, or nebulae, are composed of mostly hydrogen and helium, plus a smattering of heavier constituents, including oxygen, nitrogen, sulfur, iron, organic molecules, and various minerals. When hydrogen, oxygen, and other atoms within nebulae are excited by ultraviolet radiation from nearby stars, they glow in visible light, allowing us to see and photograph the nebulae.
Parts of nebulae may collapse gravitationally, when influenced by nearby supernova explosions, interactions between adjoining molecular clouds, or in some cases, collisions between galaxies. As parts of a nebula collapse, filaments of matter fragment into denser cores. This collapse increases temperature and pressure, and the cores become protostars. Continued collapse of protostars, in part from material flowing inward from a surrounding disk, increases temperatures further. This causes ionization and fusion of heavy hydrogen, known as deuterium. The progressing collapse increases temperatures and pressures yet higher, ultimately triggering fusion of common hydrogen, producing helium at temperatures exceeding ten million degrees F. The start of hydrogen fusion stops the collapse, resulting in an equilibrium. Thus, a new star is born. Disks of icy and rocky particles that surround new-born stars are likely the seeds from which planets, asteroids, and comets originate. Nuclear fusion in stars produces immense amounts of electromagnetic radiation, ranging from high energy gamma rays and X-rays, ultraviolet light, visible light, infrared light, and radio waves. It’s the Sun’s light, produced by hydrogen fusion, that energizes Earth’s biosphere.
So, some night this week gaze upward toward the Orion Nebula and contemplate new beginnings in our Universe!
You’ve been listening to “Western Slope Skies”, produced by the Black Canyon Astronomical Society and KVNF Community Radio. I’m Art Trevena.
https://hubblesite.org/contents/media/images/2006/01/1826-Image.html
https://science.nasa.gov/universe/stars/
https://science.nasa.gov/missions/hubble/hubble-views-a-turbulent-stellar-nursery/
https://science.nasa.gov/missions/hubble/hubble-peers-into-a-dusty-stellar-nursery/
