Bell Ringer If the sun were about the size of a golf ball, and it were placed on the goal line of a football field, where would the Earth be? Neptune? About how many Earths could I put side by side from one side of the Sun to the other? Most of space is just _____________________

Science Matters 3D printing

3D Printers “Additive Manufacturing” Fancy hot glue gun… Layer by layer Plastic / Metal Could help with a mission to Mars, use materials already there.

3D bioprinting Same principle working with cells Burn victims Organ transplants Blood transfusions

Physics 228 Galaxies

Spiral Nebulae vs. Island Universes The Great Debate: what is the nature of the spiral nebulae? Shapely vs. Curtis, April 26, 1920 at the National Academy of Science in Washington, D.C. Each scientist presented, then took part in a joint discussion. Shapley believed the spiral nebulae to be part of our own Galaxy. Curtis believed them to be separate, completely different galaxies, external to our own. Result: no clear conclusion reached. Harlow Shapley Heber Curtis

Debate Solved, Hubble 1929 Hubble found a way to measure distances of galaxies using special kinds of stars. By measuring these stars, he determined M31 (a galaxy) was almost 1,000,000 light years away. WELL outside our Milky Way Galaxy Side note: Hubble was actually a bit off. Actual distance to M31 is ~ 3 million ly.

Galaxies Galaxies are large collections of stars that are all bound together by gravity, usually by some sort of black hole in the center. They come in many different shapes and sizes. Classification used to organize galaxies to help scientists better understand them.

Classification

Spiral Galaxies Sa: big bulge, tightly wound arms, little gas and dust Sa (NGC 2841) Sb (NGC 3031, M81) Sc (NGC 628, M74) Sa: big bulge, tightly wound arms, little gas and dust Sb: medium bulge, moderately wound, moderate gas and dust Sc: small bulge, loosely wound, lots of gas and dust

Barred Spiral Galaxies SBa (NGC 4314) SBb (NGC 4548, M91) SBc (NGC 613) Sa: big bulge, tightly wound arms, little gas and dust Sb: medium bulge, moderately wound, moderate gas and dust Sc: small bulge, loosely wound, lots of gas and dust

Grand Design vs. Flocculent Spirals M81: Grand Design Spiral NGC 2841: Flocculent Spiral Grand Design: prominent, well-defined spiral arms. Flocculent: “puffy” arm structure, not well-defined arms.

Elliptical Galaxies Characteristics: Smooth, ellipsoidal, tend to be reddish (Lots of older stars) No dark dust, little gas, no spiral arms, no star formation Old stars; no unified rotation: random motions of stars. Classification label “En” where n is a number equal to 10 times the ellipticity, ε, (rounded to nearest whole number). E0 are the roundest E6 or E7 are the flattest seen a b

Elliptical Galaxies E0 (NGC 4486) E3 (NGC 4365) E6 (NGC 4564)

S0 – Lenticular Galaxies Characteristics: Intermediate between ellipticals and spirals. Flatter than ellipticals Also called “Lenticular Galaxies” Resemble spirals, but have younger stars.

Irregular Galaxies Characteristics: Amorphous, lacking in shape. Rich in gas and dust, have a lot of star formation Example: Small and Large Magellanic Clouds (SMC, LMC)

Dwarf Galaxies Dimmest galaxies. Dwarf ellipticals (dE), dwarf spheroidals (dSph), and dwarf irregulars (dIrr). An estimated 90% of the galaxies in our immediate neighborhood are dwarfs. Leo I, dwarf spheroidal galaxy, d ~ 250 kpc

Peculiar Galaxies Don’t fit into any of the classes. Often galaxy mergers. NGC 7252 Cartwheel Galaxy

https://www.youtube.com/watch?v=OVDWVJGXRIk What kind of galaxy is the Milky Way? How far across is the Milky Way? Write down one other fact you learned.