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SESK: Stuff Everyone Should Know · sesk.info/astro-hubble-tuning-fork-branches

What do the two prongs of Hubble's tuning fork represent?

They represent unbarred and barred spiral galaxies.

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  1. Young and old ellipticals
  2. Nearby and distant galaxies
  3. Unbarred and barred spirals ✔

Why: Hubble's morphology diagram places ellipticals along the handle. The fork then separates ordinary spirals from barred spirals.

Huh, didn't know that: The lenticular type S0 sits near the point where the diagram divides.

The dad joke
Hubble brought a tuning fork because galaxies have stellar arrangements.
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References

Answer: Unbarred and barred spirals. Hubble's morphology diagram places ellipticals along the handle. The fork then separates ordinary spirals from barred spirals.

  1. Types of Galaxies openstax.org/books/astronomy/pages/26-2-types-of-galaxies
    On the right, you can see the basic spiral shapes illustrated, alongside images of actual barred and unbarred spirals.
    Checked 2026-10-10.

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