The first task for this puzzle was, as usual, to identify the three pictures at the top of the puzzle page. We also, however, had to identify what order they were in; why the first one was first, for example. Here are the three pictures, with corresponding descriptions and information:
This is the picture of a nebula; specifically, the Eagle Nebula. Nebulas are the first stage in the life of a star; stars are formed within nebulas.
This picture is a star chart, showing different kinds of stars and their processions, or 'lives'. The life of a star occurs, logically, after its birth, so it makes sense that this picture follows that of the birth of a star.
This is the picture of a supernova, the death of a star. Specifically, it is of the crab nebula. One form of a star's 'death' is a supernova, so this follows the logical progression so far: Birth, Life, and Death.
The second part of this puzzle is to analyze and understand the star chart diagram:
This chart compares the relative temperature and luminosity (the amount of light given off by a star) of a given set of standard stars. This kind of chart is also known as an 'H-R' diagram. "Normal" stars, or stars that follow the "main sequence", start off their lives in the lower-right corner of the chart, and, as they burn up their hydrogen, eventually work their way up the sequence until they are at the top left corner of the graph.
Astronomers use this diagram to understand the present stage of life of stars, and to learn about stars as well. The temperature of a star can be determined by analyzing its spectrum; given the temperature of a star, and the assumption that the star follows the main sequence, the star's luminosity can be determined and its age can be approximated. The luminosity of a star, when compared to the actual star's brightness when seen from Earth, can give some idea of the distance of the star from Earth; or, if that distance is known, of the kinds of objects between here and there, obstructing the view of the star. The age of the star is also the time from when the star first formed; this time can help us understand what the universe was like in its early days.
As implied before, this chart is placed in between the other two pictures because it describes the life of an average star. As a result, the sequence of images goes as follows: Star Birth, Star Life, and Star Death.