Astronomy Notes Image From: http://www.astronomy-pictures.net/spiral_galaxy.jpg;

Stars The Sun An object made of gas that gives off energy mainly hydrogen helium The Sun medium in size & life span compared to other stars primary energy source for all processes on Earth much closer to Earth than any other star! about 4 ½ billion years old

Magnitude = how bright/luminous H-R Diagram: Shows the relationship between color, temperature, magnitude (brightness) & size of stars. Color = temperature Magnitude = how bright/luminous Our Sun is a main sequence star. Magnitude 2 of 11

2. Gravity pulls material into a sphere that becomes dense, hot Black Dwarf Iike our Sun! Nebula 1. Large cloud of gas & dust where stars form. 2. Gravity pulls material into a sphere that becomes dense, hot & ignites. 4. Outer layers come off 5. Collapses to just its core 3. Expands or Explodes! 3 of 11

Galaxy A large grouping of stars in space. 3 types Spiral – bulge in center & distinctive spiral arms Example: Our galaxy, The Milky Way Our solar system is located within an arm Elliptical – spherical or elongated Irregular 1 2 3

Terrestrial Planet: a rocky, INNER planet Our Solar System 5 of 11 Terrestrial Planet: a rocky, INNER planet Mercury closest to the sun no atmosphere full of craters very hot during day; freezing cold at night Venus Similar in size to Earth Hot, thick & poisonous atmosphere Earth – home! Mars known as the “red planet” because of its iron-rich soil

Gas Giant: large, OUTER planet that is made mostly of gases Jupiter largest planet known for its storm, “The Great Red Spot” Saturn known for its ring system Uranus known for blue-green atmosphere Neptune blue-green atmosphere like Uranus Also has a storm, “The Great Dark Spot”

Moon A natural satellite of a planet. The outer planets have many of them! Image From: http://sos.noaa.gov/images/Solar_System/moon.jpg; Definition: www.thefreedictionary.com

Other Rocky Bodies... Asteroids asteroid belt between Mars & Jupiter small, rocky body that revolves around the Sun Meteoroids – in space (like asteroids), but usually smaller Meteors – (meteor shower); a bright streak of light caused by the rock burning as it streaks through the atmosphere Meteorites – piece of rock that has landed on Earth without completely burning up, possibly making a crater Comet – a body of ice, rock and dust that forms a tail as it gets close to the Sun 8 of 11

Light Year A measure of how long it takes light to travel through space in one year. 9 of 11 Image From: http://uniqhorns.com/images/milkyway.gif; Definition: www.thefreedictionary.com

Electromagnetic Spectrum 10 of 11 Electromagnetic Spectrum The range of all the waves that can travel through matter as well as empty space. Scientists use different portions of the spectrum to learn about the universe. Ex: light waves can tell us what elements stars are made & if they are moving away or towards other objects. R O Y G B I V Image From: http://www.lcse.umn.edu/specs/labs/images/spectrum.gif Definition: www.thefreedictionary.com

Theories on the Origin of the Universe Steady State – has always been the same Oscillating Model - began by expanding, has slowed down & is now contracting Big Bang - *the dominant theory 12 to 15 billion years ago Universe began as a dense point that exploded It rapidly expanded & began to cool down, forming stars, etc. Evidence discovery of cosmic background radiation red shift in EM spectrum suggest it is still expanding 11 of 11