constellations a Ancient cultures used mythology or everyday items to name constellations 2 Modern astronomy studies 88 constellations 3 Some constellations are not visible all year because Earth revolves around the Sun ID: 748629
Download Presentation The PPT/PDF document "Stars 1. Patterns of stars –" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
StarsSlide2
1. Patterns of stars –
constellations
a. Ancient cultures used
mythology
or everyday items to name constellationsSlide3Slide4Slide5
2. Modern astronomy studies
88
constellations
3. Some constellations are not
visible
all year because Earth revolves around the Sun
4.
Circumpolar constellations
in the northern sky appear to circle around Polaris and are visible all yearSlide6
The central part of the Milky Way with summer constellations Scorpius and Sagittarius shine above Bryce Canyon National Park in southern Utah, USA.Slide7Slide8
B. Star
magnitude
Absolute magnitude—
measure
of the amount of light a star actually gives off
2.
Apparent magnitude—
measure of the amount of a star’s light received on EarthSlide9Slide10
Sirius appears to be a much brighter star than Rigel. However, the opposite is true. Sirius only appears brighter because it is one hundred times closer to Earth than Rigel. Slide11
C. Space
measurement
Astronomers measure a star’s
parallax
—shift in its position when viewed from two different angles
2. Distance is measured in
light-years
—the distance light travels in a yearSlide12
http://hypnagogic.net/sim/Sim/new-parallax/Parallax.htmlSlide13
D. Star
properties
Color indicates
temperature
Hot stars are
blue-white
b. Cool stars look
orange or red
c.
Yellow
stars like the Sun are medium temperatureSlide14
2. A spectroscope breaks the visible light from a star into a
spectrum
a. Spectrum indicates
elements
in the star’s atmosphereSlide15
The Sun’s Energy (WTD)
The energy of the Sun is derived from the fusion of H into He***
The Sun is about halfway through it’s life cycle with another 5 billion yrs left to go Slide16Slide17
Sun’s
layers
—energy
created in the core
moves outward through
the radiation zone
and the convection zone
and into the Sun’s atmosphere
B. Sun’s
atmosphere
1.
Photosphere
—lowest layer gives off light and is about 6,000 KSlide18
2.
Chromosphere
is the next layer about 2,000 km above the photosphereSlide19
3. Extending millions of km into space, the 2 million K
corona
releases charged particles as solar windSlide20
C. Surface
features
Sunspots
—dark
areas cooler than
their surroundings
Temporary
features
which come and go
over days, weeks,
or months
b. Increase and decrease in a 10 to 11 year pattern called
solar activity cycle
2. Sunspots are related to
intense magnetic fields
Videos\Sun Set GOOD.flvSlide21
Solar Eclipse Corona Slide22
Magnetic fields may cause
prominences
—huge, arching gas columns
b. Violent eruptions near
a sunspot are called
solar flares
Slide23
3. Bright
coronal mass ejections
(CMEs) appear as a halo around the Sun when emitted in the Earth’s direction
http://www.tomwujec.com/?page_id=1105Slide24
a. Highly charged
solar wind particles
can disrupt radio signalsSlide25
b. Near Earth’s polar areas solar wind material can create light called an
auroraSlide26
D. Sun is mostly
average
Middle-aged
star
2. Typical
absolute magnitude
with yellow light
3. Unusual—Sun is
not part
of a multiple star system or cluster (most of stars are binary systems) WTDSlide27
Stellar EvolutionSlide28
How I Wonder What You Are ...
Stars have
D
i
f
f
e
r
e
n
t
c
o
l
o
r
s
Which indicate different temperatures
The hotter a star is, the faster it burns its life away.
Write all this down (WTD)
Slide29
A. Classifying stars—Ejnar Hertzsprung and Henry Russell graphed stars by temperature and absolute magnitude in a H-R
diagramSlide30
1.
Main Sequence
—diagonal band on H-R diagram
a. Upper left—hot,
blue
, bright stars
b. Lower right—
cool
, red, dim stars
c. Middle—average
yellow
stars like the Sun
2.
Dwarfs and giants
—the ten percent of stars that don’t fall in the main sequenceSlide31
http://hypnagogic.net/sim/Sim/hr3/HRdiagram.htmlSlide32
A
B
C
D
B.
Fusion
of hydrogen occurs in star cores releasing huge amounts of energy
http://hypnagogic.net/sim/Sim/fusion/Fusion.htmlSlide33
C.
Evolution
of stars
A
nebula
contracts and breaks apart from the instability caused by gravity
Temperatures
in each nebula chunk increase as particles move closer together
b. At 10 million K
fusion
begins and energy from a new star radiates into spaceSlide34
2. The new main sequence star
balances
pressure from fusion heat with gravity
Balance is lost when core hydrogen fuel is
used up
b. Core contracts and heats up causing outer layers to
expand
and cool
c. Star becomes a
giant
as it expands and outer layers cool
d. Helium nuclei fuse to form core of
carbonSlide35
3. A
white dwarf
forms from the giant star
a. Helium is exhausted and outer layers escape into space
b. Core contracts into hot, dense, small starSlide36
4. In massive stars fusion causes higher temperatures and greater expansion into a
supergiant
a. Eventually fusion stops as iron is formed
b. The core crashes inward causing the outer part to explode as an incredibly bright
supernovaSlide37
5. The collapsed core of a
supernova
may form a neutron star of extremely high densitySlide38
6.
The mass of a tremendously big supernova core can collapse to a point, forming a
black hole
Gravity
is so strong not even light can escape
b.
Beyond a black hole’s
event horizon
gravity operates as it would before the mass collapsedSlide39
7. Matter emitted by a star over its life time is recycled and can become part of a new
nebulaSlide40
Galaxies and the UniverseSlide41
Galaxy
—gravity holds together a large collection of stars, gas, and dust
Earth’s galaxy is
Milky Way which
is part of a galaxy
cluster named
the
Local GroupSlide42
2.
Spiral galaxies
—spiral arms wind out from inner section; some have barred spirals with stars and gas in a central barSlide43
3.
Elliptical galaxies
—large, three-dimensional ellipses; most common shapeSlide44
4.
Irregular galaxies
—smaller, less common galaxies with various different shapesSlide45
B. The Milky Way Galaxy—classified as a
spiral galaxy
1. May contain one
trillion
stars
2. About 100,000 light-years
wide
3. Sun orbits galaxy’s core every 225 million yearsSlide46
C. Theories on the
origin
of the universe
1.
Steady state theory
—universe has always existed just as it is now
2.
Oscillating model
—universe expands and contracts repeatedly over timeSlide47
D. Universe is
expanding
1.
Doppler shift
—light changes as it moves toward or away from an object
a. Starlight moving toward Earth shifts to
blue-violet
end of spectrum
b. Starlight moving away from Earth shifts to
red end
of spectrum
2. All galaxies outside the Local Group indicate a red shift in their spectra indicating they are moving
away
from EarthSlide48
E.
Big Bang Theory
—holds that universe began 13.7 billion years ago with huge explosion that caused expansion everywhere at the same timeSlide49
Galaxies more than 10
billion
light-years away give information about a young universe
2. Whether the universe may
eventually stop
expanding and begin
contracting
is unknown