Western Slope Skies - Star-Forming Nebulae

Mar 8, 2019

Credit Art Trevena

Constellation Orion stands high in the south during these March evenings. 

Just south from the east side of the 3 stars of Orion’s belt, you may notice what looks like a fuzzy star.  Binoculars or a small telescope will show that this fuzzy star is actually a glowing cloud, or nebula.  It’s called the Orion Nebula, and the Orion Nebula is just the brightest of many nebulae in constellation Orion.  Astronomers have determined that new stars and planetary systems are forming from these nebulae even today.

At a distance of “only” 1500 light years, or 9 quadrillion miles, this region of Orion is one of the nearest sites of active star formation to Earth.  Many of the bright stars and the surrounding nebulae here comprise what astronomers call the Orion OB1 Stellar Association and the Orion Molecular Cloud.  Their chemistries and other properties reveal that these stars are, astronomically speaking, very young, less than 12 million years old.

UV radiation from Orion’s hot, blue-white stars excites hydrogen and oxygen atoms in these interstellar clouds, so that they emit red and green light, respectively, forming beautiful apparitions, like the Orion Nebula.  Dark, opaque dust clouds, rich in carbon- and silicon-bearing compounds, are also common in this region of space.  Thicker dust clouds like the Horsehead Nebula form ghostly silhouettes when photographed against more distant bright nebulae.  Infrared observations of dense clouds have revealed that the dust and gas are condensing, forming proto-planetary systems, or “proplyds.” Less dense dust accumulations tend to scatter blue light from nearby stars, resulting in reflection nebulae.  Our eyes are not sensitive to color at low light levels, so colors in nebulae are hard to see.  But modern cameras are highly sensitive, resulting in the many beautiful images of nebulae taken by both professional and amateur astronomers.

On some clear and dark March night, gaze upward towards Orion and contemplate the processes going on there now.  These are likely similar to processes that formed our Sun and our Solar System billions of years ago!

You’ve been listening to “Western Slope Skies”, produced by the Black Canyon Astronomical Society.  This episode was written and recorded by Art Trevena.

Web links:

apod.nasa.gov/apod/ap101023.html
www.spacetelescope.org/news/heic1705/
hubblesite.org/image/165/gallery
www.spacetelescope.org/videos/heic0917c/
www.spacetelescope.org/videos/heic0601a/