In the 1700s, Charles Messier, a French astronomer, spent countless hours scanning the sky in search for comets. Given the limited optical technology of the time, he occasionally came across blurry objects that appeared similar to comets, yet remained fixed in the sky. Messier carefully cataloged over a hundred of these “distracting” objects, which today are known as Messier objects and include galaxies and planetary nebulae.
Messier is certainly not alone in having a catalog of astronomical objects containing one’s name. Take those starting with ‘A’ for example: we have the Anderson Catalog (binary stars), Allen Catalog (planetary nebulae), Apriamashvili Catalog (open star clusters), Alvan Clark Catalog (also binary stars)… To me, this is a bit of a nightmare, especially considering the overlap in objects among many of these. (Check out a non-exhaustive Wikipedia list of astronomical catalogs here).
There is some hope and order, however. Given the global scale in which astronomy research takes place, the International Astronomical Union was formed to address the need for researchers to be able to communicate amongst each other with consistent naming conventions and more modern, standardized catalogs.
For objects outside the Milky Way, the convention is simple enough: an abbreviation of the catalog name, followed by a space and then an alphanumeric listing (standards here). For example, the galaxy pictured above is the 4291st object in the New General Catalog, so it is called NGC 4291.
NGC 4291 is a wind-blown galaxy located around 320 million light-years from Earth in the Coma constellation. This is one of my favorite galaxies, perhaps because the galactic dust has very little star formation activity, giving it a ghostly, starless appearance.
(These data were originally acquired for this 2006 scientific proposal, which sought to identify Cepheid variables, which are stars that help astronomers calibrate distances across the universe. I combined two 41 minute exposures from Hubble’s Advanced Camera for Surveys centered at bands 814nm and 606nm).
The galaxy below, also a spiral galaxy, shows a bit of a different story with much more active star formation. NGC 6814 is located in the Aquila constellation 75 million light-years away. The data here are from 2013, following a similar proposal to use features within this galaxy to contribute to the understanding of the scale of the universe.
Based on observations made with the NASA/ESA Hubble Space Telescope, and obtained from the Hubble Legacy Archive, which is a collaboration between the Space Telescope Science Institute (STScI/NASA), the Space Telescope European Coordinating Facility (ST-ECF/ESA) and the Canadian Astronomy Data Centre (CADC/NRC/CSA).