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Stars and Galaxies Constellations: patterns of stars Represents mythological characters, animals or familiar objects. • Modern astronomy divides sky into 88 constellations. • Stars are found in specific locations in sky … Polaris, Sirius, Betelgeuse Ursa Major; Ursa Minor and others APPEAR to circle around POLARIS (North Star) . Are visible ALL YEAR LONG Other constellations come and go in the sky due to Earth’s revolution around Sun. Absolute Magnitude: measure of the amount of light start gives OFF. Apparent Magnitude: measure of the amount of light RECEIVED on Earth. A dim star can appear bright if closer to Earth. A bright star can appear dim if it is far away from Earth. One Way = PARALLAX “The apparent shift in the position of an object when viewed from two different positions. “ THE NEARER AN OBJECT IS to the observer, the GREATER the parallax is. Example – thumb Light-year – distance light travels in 1 year = 300,000 km/s or 9.5 trillion km in 1 yr. AU – average distance Earth is from Sun = 150 million km. Luminosity – true brightness of an object. Use Luxes = measure light intensity. Closest Star to Earth? SUN After Sun, Proxima Centauri = 4.2 light years away. Color = temperature HOT are blue – white color. Cool are orange – red color Yellow – our SUN Composition = observing spectra (like a prism) Light passes thru a spectroscope (spreads light into different wavelengths) - breaks into colors (like a rainbow) w/ dark lines in between. Lines tell us what elements are in the star. Every chemical element produces a unique pattern of dark lines ~ just like a finger print. ** Can also tell energy level Low energy: newer stars emit radio & infrared waves. Higher energy: exploding stars emit ultraviolet & x-rays. Read Ch 22 Lesson 1 DO your note cards or foldables for Lesson 1 Use both NOTES & book. DO: P. 806 (1-8 only) Why so important? •Makes life possible! •Center of our System. •Source of most energy on Earth In Universe … Just an ordinary – * Yellow * Main Sequence Unique in one way: IT IS NOT BINARY (Pair of stars – orbit each other) List ~ Inside to Atmosphere A. Core: where fusion takes place – which is Sun’s energy. B. Radiation Zone: how Energy travels outward C. Convection Zone:(circulates) how Energy travels outward and circulates D. Photosphere: where light is given off (lowest layer of atmosphere) Often called the “surface” E. Chromosphere: above photosphere F. Corona : * largest layer of atmosphere. (Rays you drew off a circle when you were little ) * Charged particles escape from here and create Solar Wind. NOT smooth ! Sun rotates faster at equator than at poles. Sunspots Area that appear darker than rest. Cooler than surrounding area. Intense magnetic fields. Ever since Galileo – we’ve been studying them! Not permanent – appear and disappear. 11 yr. cycle of min. and max. # of sunspots. Prominences: HUGE, arching columns of gas. Think they are related to intense Magnetic Field of SUNSPOTS. Flares: violent eruptions ~ gases near a sunspot sometimes brighten and then shoot out at high speed. CMEs: coronal mass ejections Usually occur during Sunspot Maximums Highly charged solar wind material Cause Auroras (Northern Lights) – electrical currents that ionize gas in Earth’s atmosphere. Can disrupt radio signals; power outages, etc. Video of CMEs hitting Earth video of sun 4 min. video of explanation of how sun works •Most stars fit into MAIN SEQUENCE. •Usually: temp. is at the bottom. •Notice: Brighter stars have Magnitudes w/ neg. numbers. (Intensity goes UP.) **KNOW: hottest / brightest = top left coolest / faintest = lower right Read Lesson 2 Do note cards / foldables for Lesson 2 Do: worksheet on H-R diagram. * Two Important diagrams: NEED to know how to read them!!! #1) H-R Diagram: Hertzsprung and Russell (scientists) ▪ Stars arranged by brightness and temperature ▪ Shows (USUALLY): the hotter the star – the brighter the star. #2 ) Life of a Star Diagram – handout. * Shows how star evolves. * Two paths – depends on mass of star. Temps are so high causes Hydrogen to FUSE into Helium! REACTION causes high amounts of energy to be released. Happens in the CORE of STARS – only place w/ temps high enough. High Mass Stars NEBULA: all stars beginning Def: large cloud of gas & dust Main Sequence - most stars … until uses up its Hydrogen!! Red Supergiant - core contracts – causes temp to increase then COOLS Supernova : outer portion of star explodes (def = huge explosion that destroys a star) ▪ Neutron Star – consists only of Neutrons in dense core ▪ Black Hole – core collapses until there is no volume – gravity so great nothing can escape - not even LIGHT Low Mass Stars NEBULA: all stars beginning Main Sequence Red Giant White Dwarf - leftover core – hot dense slowly cooling sphere of carbon. Leftover material goes into a NEBULA … Matter is reused – New star is formed … Definition of Galaxy Large group of stars, gas, and dust held together by gravity. *Universe consists of hundreds of billions of galaxies. *Most galaxies are in clusters not spread evenly in universe. Types of Galaxies: Spiral : has “arms” Elliptical: looks like a football – oval shape Irregular: all the rest that don’t fit into the other 2 categories. Our Galaxy: Milky Way : Ours is w/ the Local Group (about 30 galaxies) Think it’s a SPIRAL but could be barred (have bars) Sun is NOT in center – one of the arms – orbits around EVERYTHING in space. 90 % is DARK Matter (Matter that emits no light at any wavelength.) Scientist used: Doppler Shift to learn that UNIVERSE is expanding Doppler Shift: ▪ RED – ▪ object moving away ▪ wavelengths of light stretch (expand) ▪ BLUE – ▪ object moving toward ▪ wavelengths of light compress 12 to 15 billion yrs ago, universe began w/ explosion Everything is expanding …from that explosion Once again … Catholic Scientist came up w/ the idea Review WS Thurs : TEST over Ch 22 (Got your note cards or foldables done??) You have been reviewing vocab, right?