Science, Maths & Technology
In the night sky: Orion
...HR) diagram below. The diagram plots stellar luminosity against temperature, and was first constructed by the Danish astronomer Ejnar Hertzsprung in 1906 and then, independently, by the American Henry Norris Russell, using a more extensive set of data, in 1913. Note that temperature, which is plotted on the horizontal axis, decreases from left to right. [An image shows...