3 ms·
That's the naming convention for exoplanets. It descends from the naming conventions for multiple star systems defined by the International Astronomical Union [
by tomr_stargazer 6y ago
That's the naming convention for exoplanets. It descends from the naming conventions for multiple star systems defined by the International Astronomical Union [0], in which the brightest (and usually gravitationally dominant) member of a multiple system receives designation "A", the second-brightest gets "B", and so on. Note the capitals. Planets, being considered a lower-mass extension of stars, get lower-case letters accordingly; so the first planet gets "b", the next planet gets "c" and so on. There is no lowercase "a" in a star-planet system. (I guess you might have that if you found binary planets without a star system; that would be very unusual).
Source: my PhD in astrophysics, and:
[0] https://en.wikipedia.org/wiki/Exoplanet_naming_convention https://en.wikipedia.org/wiki/Exoplanet_naming_convention
- sp332 6y agoSo in this case the binary system together is 1A? Or is the brighter star 1A, the planet is 1b, and the black hole is 1C because it's darker?
- deleted 6y ago[deleted]
- tomr_stargazer 6y agoI had to look at the paper itself to figure this out, but - in this paper, they designate the binary (star + stellar remnant) together as M51-ULS-1, and the planet actually orbits the two members together (a so-called circumbinary planet [0]). The logic of the nomenclature system actually breaks down in such cases - here's a quote from the Wikipedia article on naming conventions [1] stating as much: 'According to Hessman et al., the implicit system for exoplanet names "utterly failed with the discovery of circumbinary planets", and they state that it is unhelpful. ' So, yeah, take that for what you will. [0] https://en.wikipedia.org/wiki/Circumbinary_planet https://en.wikipedia.org/wiki/Circumbinary_planet [1] https://en.wikipedia.org/wiki/Exoplanet_naming_convention#Circumbinary_planets_and_2010_proposal https://en.wikipedia.org/wiki/Exoplanet_naming_convention#Ci...