The Great Nebula

My wife and I were walking back from a friend’s house one winter night. “Is that a nebula?” Cory asked. No, I explained, light pollution in Salt Lake City is far too bright to let us see a nebula. I’ve seen them without magnification in dark skies, but here it’s impossible.

When we reached our home she stopped. “It really looks like a nebula,” she said, pointing. No, I said — then saw where she was aiming, directly at the Orion constellation. The center “star” in Orion’s sword was fuzzy, even seen from a neighborhood with far too much light glare.

It is the Great Orion Nebula.

The Orion nebula, known as Messier 42, or M42, is the centerpiece of the winter sky. Tonight, assuming the weather is clear and the light pollution isn’t horrific, you might glimpse Orion’s glory, possibly even without binoculars.

Find the constellation Orion the Hunter, which is one of the easiest to recognize. The part we’re talking about looks like a kite with its tail hanging down. The upper left edge of the kite is Orion’s belt and the tail is called Orion’s sword. At 9 p.m. the sword glitters in the south-southeast around 40 degrees above the horizon line, discounting any mountains. Ten degrees is about the height of a clenched fist held at arm’s length, placing the sword four fists above the horizon.

(Halfway back toward the horizon and to the left is brilliant Sirius, the Dog Star. As Dave Bernson, president of the Salt Lake Astronomical Society, joked during Tuesday’s SLAS meeting, Sirius ranks as “the second brightest” star in the sky. The brightest is the sun.)

The central “star” in Orion’s sword is not a star. It’s the Orion Nebula, a vast bundle of gas and dust that contains thousands of stars.

In a modest telescope the spreading folds of gray drapery and a dazzling star cluster pop out stunningly. A long-exposure telescopic photo shows subtle, lovely pastel pinks and purples; a clump of searing large bright stars, and many scattered smaller ones. The brightest stars are fiercely hot, blazing in the early stages of their lives.

The brightest section, dubbed the Trapezium, holds four gargantuan stars that light up the surrounding nebulosity.

Here is a view of part of the Orion Nebula that I took over several nights, made of many separate images stacked on top of each other and stitched together in a mosaic. The adjacent smaller round nebula actually is part of the same cloud but has a separate designation as M43.

The Orion Nebula is not abnormally large. It’s spectacular only because of its nearness to Earth, roughly 1,500 light-years away. A light-year is the distance that light travels through space in one year, plowing along at 186,000 miles every second.

NASA says the nebula is about 40 light-years across. My photo, seen through the link above, is something like six light-years from side to side, with much of the nebula beyond the field of view.

To get an idea of nebular dimensions, consider the Tarantula Nebula, within a nearby galaxy called the Large Magellanic Cloud, 180,000 light-years away. Bernson said if the Tarantula Nebula were as close as the Orion Nebula, “it would cover a quarter of the visible sky” and would be bright enough in places to be seen in daytime.

What is the Orion Nebula? “It’s a stellar nursery,” he said.

It came about through the gravitational collapse of a vast cloud of dust and gas, with stars igniting and burning in the tighter knots of material. NASA calls it “a cavern of roiling dust and gas where thousands of stars are forming.”

I call it beautiful.

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