Download Chapter 25 - OG

Stars and Galaxies
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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
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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.
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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.
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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
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Light-year – distance light travels in 1 year
= 300,000 km/s or 9.5 trillion km in 1 yr.
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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.
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Color = temperature
 HOT are blue – white color.
 Cool are orange – red color
 Yellow – our SUN
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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.
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Read Ch 22 Lesson 1
DO your note cards or foldables for Lesson 1
 Use both NOTES & book.
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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.
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NOT smooth !
Sun rotates faster at equator than at poles.
Sunspots
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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.
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Prominences: HUGE, arching columns of gas.
 Think they are related to intense Magnetic Field of
SUNSPOTS.
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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.
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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
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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.
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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.
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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
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Low Mass Stars
 NEBULA: all stars beginning
 Main Sequence
 Red Giant
 White Dwarf - leftover core – hot dense slowly cooling sphere of carbon.
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Leftover material goes into a NEBULA …
Matter is reused – New star is formed …
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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.
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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.
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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
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EVERYTHING in space.
 90 % is DARK Matter (Matter that emits no light
at any wavelength.)
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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
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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
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Review WS
Thurs : TEST over Ch 22
 (Got your note cards or foldables done??)
 You have been reviewing vocab, right?