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 CMEs hitting Earth  video of sun video of sun  4 min. video of explanation of how sun works 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 beginningDef: 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?