The Hubble Sequence of Galaxies helps us organize them by appearance. When you don't know anything, first put them in buckets of "this one is like that one", and hope correlations appear. Here, they do! This is part of my complete intro Astronomy class that I taught at Willam Paterson University and CUNY Hunter. • Galaxy Types: Elliptical, spiral, and irregular. • Elliptical Galaxy Characteristics: Lack of spiral arms and dust lanes, composed of older stars. • Elliptical Galaxy Size and Composition: Vary in size from trillions to millions of stars, contain no gas or dust. • Lenticular Galaxies: Disc-like structure with a central bulge, lacking spiral arms and interstellar gas, often mistaken for elliptical galaxies. • Spiral Galaxies: Classified as Sa, Sb, Sc, and Sd based on the size of their central bulge and the tightness of their spiral arms. • Star Formation Indicators: Pink and blue glows in galaxies indicate star formation regions, with pink representing ionized hydrogen and bright stars forming in clusters. • Spiral Arm Features: Regions of active star formation, containing dust, gas, and young stars. • Galaxy Types and Examples: Discussion of spiral galaxies (M101, Triangulum Galaxy, NGC 3310), elliptical galaxies, and lenticular galaxies. • Observational Experience: Description of observing various galaxies through a telescope, noting their structures and the vastness of the universe. • Galaxy Identification: Spiral galaxies are identified by the presence of dust, gas, star formation, and hydrogen emissions. • Star Rotation in Barred Spirals: Stars farther from the center of a barred spiral galaxy rotate faster than those closer in. • Barred Spiral Galaxy Classification: Classification is based on the size of the central bulge and the tightness of the spiral arms. • Star Formation in Irregular Galaxies: Irregular galaxies, like M82, are sites of active star formation, often with unusual shapes and star formation patterns. • M82’s Characteristics: M82 is the brightest infrared galaxy due to intense star formation, with stellar winds driving gas out to tens of thousands of light-years. • Dwarf Irregular Galaxies: These small, dim galaxies are often distorted in shape, contain many hot, young blue stars, and are held together by a significant amount of dark matter. • Galaxy Structure and Composition: Spiral galaxies have a disk, spheroidal component, and rapid rotation, while elliptical galaxies are dominated by random star motions and lack gas and dust.