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?

SUNAfter 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 outwardC. 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 photosphereF. 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 Earthvideo of sun4 min. video of explanation of how s

un 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 2Do note cards / foldables for Lesson

2Do: 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 WSThurs : TEST over Ch 22

(Got your note cards or foldables done??)

You have been reviewing vocab, right?