The Castor-and-Pollux Gemini Dioscuri system contains several red dwarfs classified as type 'dM1e' stars.
I believe the d is dwarf, the M is M-type (redundantly designating a red dwarf?).
What do the '1' and 'e', specifically, stand for?
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Sign up to join this communityThe Castor-and-Pollux Gemini Dioscuri system contains several red dwarfs classified as type 'dM1e' stars.
I believe the d is dwarf, the M is M-type (redundantly designating a red dwarf?).
What do the '1' and 'e', specifically, stand for?
The 9 main spectral types (the classical OBAFGKM ones plus the more recent L and T ones for brown dwarfs) indicate the general features seen in the spectra and are in descending of temperature (O is hottest, T is coolest). Each spectral type is subdivided from 0 to 9 e.g. M0, M1, M2... M9, again in decreasing temperature order.
Normally there is then a luminosity class which is a Roman numeral from I (supergiants) to V (dwarfs) except in this case, they have indicated the dwarf nature with a 'd' prefix instead. (Since you could have a M giant e.g. a M1III with similar surface temperatures and therefore spectral appearance, the M-type doesn't redundantly designate a dwarf star).
Finally there is a series of suffix letters for unusual features in the spectra. In this case this is 'e' for "emission lines present" - there is a table of these, along with brief summaries of the other parts of the spectral type classification at this site.