Astronomy is filled with ideas that share too many different names. For instance, an Quasar is also a QSO is also an Active Galactic Nuclei. In our solar system, where we once had a bunch of specific objects, we now have terrestrial planets, gaseous planets, asteroids, and icy bodies (and 1 star too). As science starts to understand more and more about our universe, we’re finding that more and more of the things we used to break into many small groups are really different versions of the same object just seen from different vantages or in different environments.
This is scientifically a wonderful thing: Being able to understand what a black hole that is actively feeding looks like as a function of feeding rate and angle of view allows us to say something based on the physics of the system, where as having a bunch of names associated with a bunch of different images is more like leaf collecting without taking DNA samples. Being able to understand how an icy object looks in the solar system both when it is out near Pluto, and when it is making a plunge past the Sun allows us to see how materials get distributed through the solar system. The more we learn, the more we see everything can be broken down into a series of fewer and fewer large boxes.
It is unfortunate, however, that our understanding didn’t come before we had a chance to come up with 40 million names for what we now know are related objects. For instance, all of the following objects are active galactic nuclei: QSOs, Qausars, Seyfert 1s, Seyfert 2s, BL Lac objects, Blazers, and LINERs. Similarly, novae, dwarf novae, classic novae, recurrent novae, Z Cam objects, U Gem objects, and SU Urs objects are all types of cataclysmic variables. The journey to our understanding was a long one, and it came by bringing together many small groups of objects, one at a time, and seeing that at their core they are all the same.
What we are realizing there is a taxonomy of the sky. Just as I am a [mammal, primate, hominid, homo sapiens], a star system might be [binary, cataclysmic variable, U Gem object].
But while we have a clear and agreed upon language for discussing the names of biologicals, such a precise language doesn’t yet exist in astronomy. If I want to find all the latest papers on galaxies with actively feeding supermassive black holes that have observable broad and narrow line absorption regions and tiny little radio jets, I need to search on the terms active galaxy, radio galaxy, Seyfert 1, and active supermassive black hole. This lack of precision in language slows the progress of research. One team may make huge strides, developing their own methods and vocabulary and publishing in one set of journals with one set of keywords, while another group makes parallel and complementary progress, developing different methods and vocabulary while publishing in a different set of journals with another set of keywords. If the teams don’t happen to meet at a conference or have someone point out one another’s work, it could be a couple years into the research before they realize they are doing something that would greatly benefit from collaboration.
As our ideas are unifying we need to take care to unify our language as well. We need to take care to use all appropriate keywords and not be lazy as we check boxes, and we need to take the time to do literature searches on every possible archaic turn of language as well. Even though we now know Andromeda is a galaxy (really, it is), there are those that still call it the Andromeda Nebula. It won’t be easy to change our language habits, but it will be good for the soul (or at least good for those of us doing literature searches) if we can find a way to manage it.