Stamp Collecting

One thing astronomers do is attempt to classify the objects they see by common properties. For example, stars that display similar chemical fingerprints in their spectra will be assigned a certain spectral type. Galaxies can be grouped by shape such as spiral, barred spiral, elliptical, and my favorite, irregular. Here’s a chart from NASA showing the numbers of exoplanets discovered as grouped by size of planet.

[image error]

Back in my college days, we called this “stamp collecting.” It’s a somewhat dero...