Hubble’s galaxy classification diagram (the “tuning fork”)
A suggests the existence of black holes
B shows how galaxies evolve from one form to another
C relates galaxies according to their shapes, but not according to any evolutionary status
D explains active galactic nuclei
The correct answer and explanation is :
The correct answer is:
C) Relates galaxies according to their shapes, but not according to any evolutionary status.
Explanation:
Hubble’s galaxy classification diagram, also known as the “tuning fork” diagram, was developed by Edwin Hubble in 1926 to categorize galaxies based on their visual appearance. The diagram arranges galaxies into three main categories:
- Elliptical Galaxies (E) – These are smooth, featureless galaxies that appear elongated or spherical. They are labeled from E0 (nearly spherical) to E7 (highly elongated).
- Spiral Galaxies (S and SB) – These have a distinct central bulge and spiral arms. They are further divided into:
- Regular Spirals (S): With well-defined arms.
- Barred Spirals (SB): Featuring a bar-like structure through the central bulge.
- Lenticular Galaxies (S0) – Intermediate galaxies that share properties of both ellipticals and spirals but lack spiral arms.
Why Option C is Correct:
- The tuning fork diagram does not indicate an evolutionary sequence. Although it appears to show that galaxies might transform from elliptical to spiral forms, Hubble himself did not intend this as an evolutionary track. Instead, it is a morphological classification system based purely on shapes and structures.
- Later studies have shown that galaxies evolve primarily through mergers and interactions, rather than following a single path in the tuning fork diagram.
- Option B is incorrect because galaxies do not evolve in a simple sequence from elliptical to spiral.
- Option A is incorrect because the diagram does not address black holes.
- Option D is incorrect because it does not explain active galactic nuclei (AGN).
Thus, Hubble’s classification relates galaxies based on shape without implying evolutionary links.