APOD 3.4

Star Colors in Orion (11 Feb. 2011)

This picture shows the stars in the constellation Orion. This photograph shows the stars kind of smeared out because the photographer used a photographing technique called a step-focus technique. This technique requires the photographer to take a series of 35 consecutive exposures. When combined, these exposures make trails of stars moving from left to right through the frame that changes focus in steps. Starting and ending with the camera out of focus makes a sharply focused exposure near the middle of the series which is why it resembles the shape of a bowtie. In the upper left, is the red supergiant Betelgeuse. Below center is the pinkish Orion Nebula, and near the center right edge is W Orionis.

This picture was interesting because it's related to what we just learned in class, how stars are different colors and why. The red stars, like Betelgeuse, appear red because they are cool. They have surface temperatures around 3,000 K. Blue stars are hotter and have temperatures over 30,000 K. But it's size and distance away affects how bright it actually appears to us. It was also interesting to learn about this photographing technique and how they photograph stars to see their true colors. In this photograph, you can easily distinguish the different colors of the stars and how bright they appear. Although, there may also be other factors that contribute to the color like W Orionis. It's red color is enhanced by it's carbon-rich composition.