Lecture Notes: CH 25 Stars and the Universe
25.1 Properties of Stars
A constellation is an apparent group of stars originally named for mythical characters. The sky contains ______constellations.
Star Color and Temperature
______is a clue to a ______.
Stellar Brightness
Apparent Magnitude- is the brightness of a star when viewed from Earth.
Three factors control the apparent brightness of a star as seen from Earth: ______it is, how ______it is, and how ______ it is.
Absolute Magnitude- is the apparent brightness of a star if it were viewed from a distance of 32.6 light-years (or 10 “parsecs”).
A binary star - one of two stars ______of mass (under their mutual gravitational attraction).
______of all stars in the Galaxy (Universe?) are part of a Binary star system
Measuring Distances to Stars
Parallax -slight ______of a star due to the orbital motion of Earth.
The ______have the ______, while those of distant stars are too small to measure.
A light-year is the distance light travels in a year, about ______kilometers.
Fill in the boxes for the H ______R ______diagram:
Note: Mass is key to where a star spends it time but also how it will die!
Describe the location, temperature and luminosity of the Sun ______
25.2 Stellar Evolution
The Life Cycle of Stars - Birth
- ______are the ______place of stars.
- ______continues to make gas (hydrogen) ______and build up pressure.
- When the ______is large enough (1 x 1026 kg) the gravity increases and temperature increases. This ______temperature (______degrees) starts fusion (______atoms ______and become Helium atoms) which ______a lot of ______.
- The cloud lights up and a ______!
The Life Cycle of Stars – Middle Age
- During this time, the star is fusing its hydrogen into helium. It takes millions and billions of years to fuse most of the H into He.
- The ______of heat of fusion ______each other and the star’s volume remainsconstant.
The Life Cycle of Stars – Death
When a star begins to ______, it ______and gravity compacts __
It will then swell to ______of times its original size.
This is called a ______(at the core ______into ______and ______). (called Red Giants because their ______than normal stars and therefore give off red light.) If and when our Sun becomes a Red Giant, the outer edge of the Sun will _____
______(and end all life on Earth) about ______years from now!
When totally ______, the star will die in 1 of 3 ways according to star size:
______DWARF: (______star- low mass); Gravity pressure is ______strong enough to fuse carbon or oxygen into anything. (The star glows white hot for thousands of years and then eventually cools and ______to a ______).
SUPERNOVA: with a more ______– (8X Mass of our Sun ); Gravity compaction produces higher fusion reactions – ______and oxygen ___ silicon and ___.
______: (4H1 He4 4He + 4He 8Be + 4He 12C
12C + 4He 16O Fe (MAXIMUM for star)
When the fusion stops, gravity pushes inward and….
*The result is a massive explosion!
It turns into either a: ______star (______mass) OR
If star turns into a______HOLE: ( its ______has a ______); Same process as medium to large star except the leftover core is so large and dense that ______escape it’s gravitational forces.
*If you enter a black hole, you would be ripped apart, atom by atom, by the intense gravity. (______)
DRAW - STELLAR DEATH - BELOW
Star Facts
•Different stars age at ______. The rate ______and the speed of fusion (hydrogen consumption)
•Stars that are ______and live shorter lives.
•Stars that are less massive burn dimmer and ______lives.
•______-sized stars live about ______years; they’re still around from the Big Bang but too dim to see.
•______-sized stars live about ______years (like ______).
•______-sized stars live about ______years; more than ______at night are massive bright stars.
Where do the atoms in you come from? ______
A star is born when______
When a giant star with A VERY HIGH MASS dies it becomes a(n)
25.3 The Universe
The Milky Way Galaxy
A galaxy is a group of stars, dust, and gases held together by gravity.
______of the Milky Way• large spiral galaxy whose disk about ______and about 10,000 light-years thick at the nucleus.
WE ARE located about ______
Structure of the Milky WayRadio telescopes reveal that the Milky Way has at least three distinct spiral arms, with some splintering.
______Types of Galaxies
•Classified by shape:
–Spiral: disk shaped ______
–______: spherical or egg shaped and ______than spiral galaxies. Contain mostly old stars and are red in color.
–Irregular: do not have a well defined shape or color (between S & E?).
Gravity holds galaxies together in clusters
•Galaxies are ______through the universe. They are grouped together in ______.
GALAXIES: a ______that are relatively close together and move as a unit.
THE UNIVERSE
SuperclusterCluster Cluster Local Group of Galaxies
Of Galaxies
GALAXY GALAXY Andromeda OUR GALAXY (Milky Way)
Our Solar System Other star systems
HOW DID THE UNIVERSE BEGIN?
•Big Bang THEORY: ______years ago a massive ______sent matter and energy traveling into space. After billions of years, the matter in the universe ______to a point where it could ______into ______and other bodies, including YOU!.
Everything is ______, including SPACE!
What happened BEFORE the Universe began? ______
Supporting ______
- The ______of galaxies supports the Big Bang and the expanding universe theories.
- Scientists discovered a type of energy called ______radiation. Scientists think that this radiation/heat was produced during the Big Bang.
- ______have changed
Red Shift, or a ______end of the spectrum, occurs because the light waves are “stretched,” which shows that Earth and the source are ______from each other.
Hubble’s law is a law that states that the galaxies are retreating from the Milky Way at a speed that is ______.
• The ______of distant galaxies indicate that the ______.
The position of the stars (galaxies, actually) have been tracked______; if you input star locations into a computer and ask it to trace current star positions ______to where they were plotted hundreds of years ago, and then extend that star/galaxy’s path back, the ______to a “single point” about 13-15 billion years ago.
But where is the center of the Universe? ______
Not including the Sun, the closest stars to Earth are ______
Which statement is not true of the Milky Way galaxy? ______
An observation of the Red Shift of galaxies suggests that the universe is ______
TRY TO DRAW A PICTURE OF THE BIG BANG over time Below