Study of the universe (Earth as a planet and beyond)

 Stars produce energy through nuclear fusion. This requires extreme heat and pressure.  A star is born when the temperature hydrogen can fuse into helium is reached (~120 million Kelvin) FUSION

 Fusion force outward = gravitational force inward (forces are balanced and stable)  Once the star runs out of hydrogen in the core, the star is UNSTABLE and begins to die.

Temperature of stars is indicated by COLOR Blue = highest energy = hottest Red = lowest energy = coolest

Luminosity (actual brightness) is impacted by 2 variables: TEMPERATURE & SIZE Higher temp = higher luminosity Bigger size = higher luminosity

 Apparent Magnitude – how bright a star appears to us on Earth (does not indicate actual luminosity)  Absolute Magnitude – how bright a star would appear if all stars were equal distance away

H-R diagram allows astronomers to determine the stage in a star’s life cycle based on where it falls on the diagram. Based on temperature and absolute magnitude. **About 90% of stars on the H-R diagram are main sequence**

 Formation of the Solar System: Formation of the Solar System:

 A large gas cloud ( nebula ) contracted through gravity  The sun formed in the center  ‘Seeds’ of matter began to clump together in a disk, and their gravity attracted more matter, eventually forming planets  Solar wind blew the remaining dust away.

1. Stars begin formation in a nebula –a cloud of gas and dust

2. Protostar – gases contract, heat up (fusion has NOT started yet in the core)

3. Main Sequence – hydrogen fusion has begun in the core; star is STABLE

4. Red Giant - Hydrogen runs out in core, fusion stops, gravity wins - Star begins to collapse, which causes enough heat and pressure to begin helium fusion in core - Star expands and cools **Star is UNSTABLE and is dying**

5. Nova – explosion of a low mass star, which leaves behind a… Planetary nebula –a cloud of gas and dust surrounding the star’s remnant core

White dwarf- very dense carbon-oxygen core left behind after the nova of a low mass star **The size of the Earth but the mass of the sun!

1. Nebula  2. Protostar  3. Main Sequence  4. Red Supergiant  ….

Once the core of the red giant runs out of helium, if the temperature is high enough it can begin fusing even heavier elements. Chain of nuclear fusion: Stable stars: Hydrogen  Helium Dying stars: Helium  Carbon  Heavier Elements  Iron Iron is the heaviest element that can be fused in the core of a star.

5. Super Nova – massive explosion of an unstable high mass star; source of heavy elements

FUSION in the cores of STARS! Teachers' Domain: The Elements: Forged in Stars (4 minute video) Teachers' Domain: The Elements: Forged in Stars (4 minute video)

6a. Neutron Star (Pulsar) – EXTREMELY DENSE rapidly spinning core of a massive star left behind after a super nova explosion **measures only 10 miles across with 300,000 times the gravity of earth and about 1.5 times the mass of our Sun!

6b. Black hole – final stage of an extremely massive star, with a gravitational field so intense that even light cannot escape **smaller than the City of Stafford!

1. Higher star mass = faster fusion reactions = shorter life span (usually hotter & brighter) 2. Lower star mass = slower fusion reactions = longer life span (usually cooler & dimmer)

Star Size Comparison:

 … and how do scientists think it came to be there?

Big Bang Theory – theory that the universe started from a single point, and has been expanding ever since.

Structure: Universe  Galaxy Superclusters  Local Group  Milky Way Galaxy  Solar System

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1. How many solar systems are in our galaxy? So far.. about 150 with new discoveries every year 2. How many stars are in our galaxy? billion 4. How many galaxies are in the universe? Hubble has observed over 3000, but it is estimated that there are over 500 billion!

Earth to Sun: 93 million miles or 1 Astronomical unit (AU) ** 8 minutes for sunlight to reach Earth ** 8 minutes for sunlight to reach Earth Solar System (from Sun to Keiper Belt): 40 AU **takes 5 ½ hours for sunlight to reach Pluto **takes 5 ½ hours for sunlight to reach Pluto Outside of our solar the distances are so great we have to use a new unit: the light year. (LY)

Sun to next nearest star (Alpha Centauri): 4.3 LY Milky Way Diameter: 100,000 LY Sun to Andromeda galaxy (nearest galaxy): 2.9 million LY Limit of observable universe: about 15 billion LY

The Electromagnetic Spectrum (light)

Stars emit all wavelengths; all types of electromagnetic radiation. The only type you can see is visible light! Where does this energy come from???? FUSION

The Electromagnetic Spectrum: Looking Through Galactic Space Clouds:

a. Wavelength represented by color b. Highest energy (shortest wavelength) = (shortest wavelength) = BLUE BLUE c. Lowest energy (longest wavelength) = (longest wavelength) = RED RED Teachers' Domain: Wavelength (quick interactive) Teachers' Domain: Wavelength (quick interactive)

ELEMENTS: Every element emits its own characteristic spectrum (fingerprint) 1. We can use this to determine the elements that make up the atmospheres of stars and planets!

MOTION: Can determine the speed & direction of moving celestial objects Doppler effect – apparent change in wavelength of radiation or sound that indicates whether an object is moving towards or away Understanding the Doppler Effect: =WCEhidp8tiA =WCEhidp8tiA

Red shift - wavelength stretches as objects move away from each other, shifting the visible spectrum to the red end Blue Shift - wavelength shortens as objects move toward each other, shifting to the visible spectrum to the blue end