Stars

Stars Star: a large celestial body that is composed of gas and that emits light.

Stars

States of Matter Temperature is a measure of energy Low energy = Solid Medium energy = Liquid High energy = Gas Higher energy = Plasma Plasma gives off light: lightning, flames, fluorescent light bulbs, northern lights, stars

Nebula Clouds of gases and dust Mostly hydrogen Birthplace of stars and solar systems

Protostar Nebula collapses and pressure/temperature builds Fusion Begins

How a Star Works Nuclear Fusion At 15,000,000 oC hydrogen atoms (protons) fuse to form helium A small amount of matter (solid stuff) is converted into energy Einstein figured out how much energy: E = mc2

Gravitational Collapse Gas pressure and heat push outwards Gravity pulls inward Equilibrium (everything equal or balanced)

New star clears out the nebula

Stars

The Hertzsprung-Russell diagram (HR Diagram)

Light Year A light year is the distance light travels in one year Light travels at 186,000 miles each second One light year is 5,869,713,600,000 (that’s almost 6 trillion miles!) The sun is 8 light minutes away from Earth. The next closest star to Earth is 4 light years away.

Dwarf Stars Variety of “colors”. Most common type. Yellow Dwarf includes our own sun Brown Dwarf – failed stars that never heated up enough to explode into a normal star White Dwarf – collapsed stars that are slowly burning away the last of their fuel Black Dwarf – non-luminous (no light) dead stars

Brown Dwarf “Almost” star Bigger than a Jupiter-type planet, smaller than a true star Hot core, but not star-hot No (or little) fusion

Red Dwarf Small, cool star Longest life span >10,000,000,000 (10 billion) years Most numerous Active fusion in core

Yellow Dwarf Our sun Active fusion in core Lifetime about 10,000,000,000 years Our sun is about 5,000,000,000 old

Red Giant After a yellow dwarf burns up its fuel it cools and contracts Temperature again rises and the star expands rapidly Becomes a red giant Our sun will be about the size of the Earth’s orbit (bye bye Mercury, Venus, Earth!)

Giants – Super Giants Giants Super Giants 1 thousand times brighter than the sun 200 times larger Super Giants 10 million times brighter Thousands of times larger

Binary Stars Two stars orbiting each other Most common form of stars in the Milky Way Jupiter 2 – 3 times more massive, we (don’t) exist in a binary star system

Binary White Dwarf System

Alpha Centauri – Proxima Centauri Earth’s next closest neighbor star – 4 light years away

Planetary and Astronomical Scales

Supernova Massive stars Rapidly uses up hydrogen, fuses larger atoms Requires energy instead of giving off energy Stellar collapse causes rapid increase in pressure and temperature Star explodes Inner layers compressed into extremely tight ball of matter

Supernova Visible X-ray

Neutron Star Neutron Star (Super Massive…Heavy!!!) Under collapse, protons and electrons combine to form neutrons. 10 km across

Black Hole Mass of core > 5 x Solar mass Gravitational force so strong not even light can collapse Center of most galaxies Eats other stars Not even compacted neutrons can support weight of very massive stars

Pulsars Neutron star that emits EM Radiation – radio – gamma Pulse rotates rapidly causing the signal to fade in and out Pulses occur as often as once per second

X-Ray Binaries In close binary systems, material flows from normal star to Neutron Star or Black Hole. X-rays emitted from disk of gas around Neutron Star/Black Hole.

Star Groups Constellations: one of 88 regions into which the sky has been divided in order to describe the locations of celestial objects; a group of stars organized in a recognizable pattern.

Galaxy Galaxy: a collection of stars, dust, and gas bound together by gravity.

Galaxies You are here.

Spiral Galaxies Spiral Galaxy: the most common type, where there is a nucleus of bright stars and a flattened arms that spiral around the nucleus. The arm consists of young stars, gas, and dust.

Milky Way = Our Galaxy Around 100,000,000,000 stars Spiral Galaxy 100,000 light years across

Elliptical Galaxies Elliptical Galaxies: are extremely bright in the center and do not have spiral arms. Elliptical galaxies have few young stars and contain little dust and gas.

Irregular Galaxies Irregular Galaxies: have low total masses and are fairly rich in dust and gas. (only a small percentage of total galaxies)

Quasars Quasar: quasi-stellar radio source, a very luminous object that produces energy at a high rate. (very distant objects located in the center of galaxies)

The Big Bang Theory Cosmology: the study of the origin, properties, processes, and evolution of the universe.

Hubble Space Telescope Research The Hubble Telescope allowed researches to see that hundreds of galaxies have large red shifts; therefore, they are moving away from earth very fast.

The Universe is Expanding!

The Big Bang Theory Big Bang Theory: the theory that all matter and energy in the universe was compressed into an extremely small volume that 13 to 15 billion years ago exploded and began expanding in all directions.

The Big Bang Theory Cosmic Background Radiation: radiation uniformly detected from every direction in space, considered a remnant of the big bang.

Dark Energy / Dark Matter Dark Matter: matter that does not give off light but that has gravity that we can detect. (23% of the universe) Dark Energy: acts as a force that opposes gravity.

And the rest…