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Venus, the “evening star,” blazes in the west as night falls this evening. And if you look carefully, you’ll see another famous celestial object close to its upper right — the Pleiades star cluster.
The eye alone reveals several bright stars that form a tiny dipper. But long-exposure photographs show many more stars, all surrounded by a blue glow — a veil of dust known as a nebula.
There are several kinds of nebulae — vast clouds of gas and dust that fill the space between stars. The Pleiades is surrounded by a reflection nebula. It consists of tiny grains of dust. These grains are the right size to scatter blue wavelengths of light. It’s similar to what happens in Earth’s atmosphere — molecules of air scatter blue light, which is why the sky looks blue.
Another prominent nebula is well to the left of Venus and the Pleiades, a little below the three-star lineup of Orion’s Belt. The Orion Nebula is bright enough to see with the eye alone. It looks like a fuzzy star.
It is an emission nebula — one that produces its own light. It’s part of a giant nursery that’s given birth to thousands of stars. The hottest, brightest stars zap the leftover atoms of hydrogen gas, causing them to glow.
There’s one other type of nebula — a dark one. Its gas and dust are so cold that they don’t produce any visible light. Instead, the dust grains absorb the light of the stars behind them - creating dark “voids” in the night sky.
Script by Damond Benningfield, Copyright 2015