Transcript Stars, Galaxies, and the Universe

Stars, Galaxies, and the
Universe
Chapter 22
Page 752
Lesson 1 The Sun
Local star-only star in our solar system
Produces energy from hydrogen
Much larger than any planet
Contains 99.9% of the mass of solar system
Has layers and atmosphere
Has sunspots and solar winds
How is energy produced from the
Sun?
Consists mostly of hydrogen and it turns
into helium to produce energy
 This change is created when hydrogen
particles collide (fusion)
 The energy is the source of light and
warmth that make life possible on Earth

Sun’s Interior
Core: Center of Sun made from dense
gas, temps of 15 million degrees Celsius
 Radiative Zone: Thick layer that energy
passes through, hot and dense, no fusion
occurs
 Convection Zone: transfers energy by
moving heated gas/liquid (convection),
carry energy to surface

Sun’s Exterior
Outer layers are the Sun’s atmospheremuch less dense
 Photosphere: Visible layer of Sun, bumpy
texture
 Chromosphere: Thin middle layer, gives off
a pinkish light
 Corona: Outer layer, extends several
million kilometers
(p. 757)

Sun’s Features
Magnetic fields: near surface
 Sunspots: on photosphere that are cooler
areas
 Flares: eruptions of hot gas from the
surface, near sunspots
 Prominences: huge loops of gas that
extend to the corona
 Winds: electric particles that flow from the
corona

Auroras
When solar winds enter our atmosphere,
they release energy, which can produce
beautiful glowing light in the sky.
 Sometimes referred to the northern or
southern lights since they occur near the
poles.
 Can destroy orbiting satellites and harm
astronauts

Interesting Facts
Takes sunlight about 8 minutes to reach
Earth
 Can only see chromosphere and corona
light during solar eclipse
 Sunspot activity lasts about 11 years
 Solar winds extend throughout our
atmosphere

Lesson 2 Stars
Stars change over their life cycle
 Classify stars by their characteristics
 Like our Sun, stars are huge balls of
glowing gas that produce energy by fusion
 Stars look like small points of light
because they are very far away
 Amount of light from a star and distance
determine brightness to us

Light Year
Distances between stars is measured in
light years by astronomers
 It is the distance light travels in a year
 9.5 trillion kilometers or 6 trillion miles
 Outside solar system, the closest star to
Earth is about 4 light years away

Parallax
Another way astronomers measure
distance
 Shift in position of an object when viewed
from different locations
 Plot positions from opposite sides of Earth

Star Size
Giant and supergiant – larger than SunBetelgeuse
 Dwarf-much smaller than the Sun
 Betelgeuse is one of the brightest stars
even though it is 522 light years

Color/Temperature
Most stars appear white
 Some are blue or red
 Temperature determines color
 Cool-red, Hot- white, In between-blue
 Chart on page 765

Life Cycle of a Star
Stars are not permanent
 Birth, maturity and death
 Varies depending on the mass of the star

Birth-Death
Form inside a cloud of gas and dust
(nebula)
 Matter does not disappear at death
 Matter forms another nebula or combines
with an existing star

Neutron Star
Collapsed core of a supergiant star
 Emits visible light
 High mass star

Black hole
A star with an extremely high mass leaves
behind an invisible hole
 Astronomers can sometimes detect matter
and energy around the hole

Star Systems
Most stars do not exist alone
 Stars are held together by the force of
gravity between them
 Binary system has 2 stars
 Multiple system has more than 2 stars

Lesson 3 Galaxies
Galaxies have different sizes and shapes
 Our solar system lies within the Milky Way
galaxy
 Galaxy is a huge group of stars, gas and
dust held together by gravity
 Milky Way is shaped like a disk with a
bulge
 It has a hazy appearance

Types of Galaxies
Spiral
 Elliptical
 Irregular
 Pictures on page 772

Center of Galaxies
Most large galaxies seem to have
supermassive black holes at their centers
 Milky Way black hole = 3 million times the
size of the Sun
 Distant galaxies have bright centers called
quasars
 Quasar means “seems like a star”
 Galaxies sometimes collide

Lesson 4 Universe
Galaxies are moving farther apart in the
universe meaning the universe is
expanding
 Universe is all space, energy and matter
 The universe does not expand into
anything since there is nothing outside the
universe

Doppler Effect
Change in the observed wavelength or
frequency of a wave that occurs when the
source of the wave or the observer is
moving
 Occurs with light and sound
 Light wavelengths will seem stretched of
compressed while moving (p. 777)

Review
Read and study page 780
 Review on page 781 # 9-20

Keep notes titled, legible and organized
 Bring notes to class
