• Question: How many different types of stars are there?

    Asked by anon-252361 to Tom, Ry, Paula, Miriam, Chris on 4 May 2020.
    • Photo: Ry Cutter

      Ry Cutter answered on 4 May 2020:

      This is a controversial question! It depends who you ask. Stars are broken into four categories:
      –
      Main sequence*
      Post-Main sequence (AGB stars, Red-giants, subgiants, supergiants, horizontal-branch)
      Dead stars (White dwarfs, Black holes, Neutron stars)
      Pre -main sequence** (Brown Dwarfs, protostars, sub-dwarfs)
      –
      * Main sequence stars are split-up by what we call their spectral type. This means what colour is the star!
      –
      O-type = big blue stars! (Hottest)
      B-type = big blue-white stars
      A-type = biggish white stars
      F-type = White-yellow stars
      G-type = Smallish Yellow-orange stars (our sun is this type!)
      K-type = small orange-red stars
      M-Type = tiny red stars! (The coldest star)
      –
      **Pre-main sequence is often referred to as sub-stellar objects. These are technically not stars because they aren’t fusing hydrogen (they aren’t heavy enough to ignite fusion!)
      –
      All of the classes listed here are split further into sub-groups… but we’ll be here for years if I do that! (for example white dwarfs can be split into DA, DB, DO, and each main sequence has a subsub type. Our sun is a G2V star… it gets messy quick :D)
      –
      Fantastic Question,
      Ry

    • Photo: Miriam Hogg

      Miriam Hogg answered on 5 May 2020:

      Ry has given a very thorough answer but just to add that we have a diagram called the hertzsprung russell diagram (or HR diagram) which graphically represents Main sequence, and post main sequence stars, including white dwarfs.

      It should be noted that the white dwarfs get thier own classification based on the element in thier outer most layer (hydrogen, helium and occasionally carbon) so they dont follow the OBAFGKM classification that the main sequence and giant stars do.

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