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Lab 11: Galaxies and Clusters of Galaxies

Part 1- Galaxy Classification:

The method of classifying galaxies devised by Hubble is called the [Hubble Tuning Fork].

2 Major Classifications of Galaxies:

1. Elliptical (E): Have a [halo] distribution with a [NON-DEFINITE] structure.



2. Spiral (S): Have a [disk] distribution with a [DEFINITE] structure. All stars, gas, and dust are concentrated in the [disk].

Sub-classifications of galaxies:

Elliptical
	E0 = Spherically shaped
	E1...6 = Increasing "Flatness" of Shape
	E7 = Very Flattened
Spiral
	Normal (S)
		Sa = Large nucleus, Arms tightly wound
		Sb = Medium-sized nucleus, Arms not so tightly wound
		Sc = Smaller nucleus, Arms loosely wound
		Sd = Very small nucleus, Wide-opened arms
	Barred (SB)
		SBa = Strong bar, Large nucleus, Arms tightly wound
		SBb = Medium-strength bar, Medium-sized nucleus, Arms not so tightly wound
		SBc = Faint bar, Smaller nucleus, Arms loosely wound
		SBd = Slightly detectable bar, Very small nucleus, Wide-opened arms

Part 2- Distance to Galaxy Clusters:

Clusters of galaxies are groups of galaxies that are [gravitationally bound] together.

When looking at the Virgo cluster, we assume that the galaxies in this cluster are at the [same distance].

Another key idea that we need to consider is that the angular size of a cluster will depend on its [distance], assuming their [True Sizes] are the same. (Refer Lab 4)