Constellations are groups of stars, sometimes in patterns of animals, or objects. Constellations are important because they can help define where in the sky astronomers are looking. (point of reference) Lesson 1: The View from Earth

Remember that waves transfer energy. The amount of energy transferred has to do with the wavelength and frequency. On one end of the spectrum are radio waves which have a longer wavelength and therefore transfer lower energy levels. On the other end of the spectrum are Gamma rays which have a much shorter wavelength and higher frequency and therefore transfer energy at a much faster rate.

Parallax is the apparent change in an objects position based on viewing it from different angles. Astronomers use parallax angles to measure how far objects are in space.

Astronomical units are used to measure distances within our solar system. To measure much greater distances outside our solar system, scientists use light years. Light years are equal to the distance light travels in a year.

1 AU = 149,598,000 kilometers (distance from Earth to Sun) 1 light year = about 9.5 to 10 trillion kilometers The sun is 109 times the diameter of Earth and about 8 light minutes away. Jupiter is about 40 light minutes away Pluto is about 40 AU from the Sun or 5.5 light hours out The next star is 4.5 light-years away! The center of the Milky Way is 25,000 light-years away. Some perspective...

 The apparent magnitude of a star is the measure of how bright it appears from Earth. Apparent Magnitude  The absolute magnitude of a star is the actual brightness of that star.  Scientists usually relate the brightness to the sun.  The term Luminosity is related to absolute magnitude.

How do stars shine?

Interior of Stars Core: hydrogen is fused into helium, some massive stars have iron cores. Radiative Zone: shell of cooler hydrogen above the core Convection Zone: where hot gas moves up toward the surface and cooler gas moves quickly into the interior. Atmosphere of Stars Photosphere: apparent surface of the star. Chromosphere: orange – red layer of a star’s atmosphere Corona: wide, outermost layer of star’s atmosphere. Highest temperature of all 3 atmospheric layers. (crown) Know these layers! Do these layers remind you of another structure you have learned bout?

Globular Cluster Open Cluster Binary

Stars are classified to learn about their past, composition, and future. Stars can be classified by temperature, color, luminosity (brightness), and mass (size)

The H-R diagram classifies stars based on luminosity and temperature. This classification helps scientists determine a stars approximate distance from Earth.

1. What would an astronomer use to explain the distance from the Sun to the planet Neptune?

2. What is the difference between the terms astronomical unit and light year? A. light years measure distances within the solar system but AU are used to measure distances outside it. B. AU years measure distances within the solar system but light years are used to measure distances outside it. C. light years are a much smaller number than astronomical units. D. astronomical units are a much larger number than light years.

3. The term used to describe a stars actual brightness is... A. apparent magnitude B. brightosity C. absolute magnitude or luminosity D. constellation

4. Which answer has the terms in the correct order from smallest object to largest object? A. planet, star, constellation, galaxy, universe B. planet, star, constellation, universe, galaxy C. star, planet, constellation, galaxy, universe D. planet, constellation, star, galaxy, universe

5. The layer of the sun that we see from Earth is the.. A. core B. corona C. photosphere D. radiative zone

6. Which characteristic is related to a stars color? A. mass B. temperature C. luminosity D. composition

7. The layer of the sun where hot gas and cooler gas are circulated is ________________. A. radiative zone B. corona C. photosphere D. convection zone

8. Apparent magnitude is determined by A. distance from Earth (or viewing point) B. distance from the Sun C. actual brightness or luminosity D. color of star

9. When determining luminosity, a _______________ number has the most brightness. A. higher B. negative C. positive D. even

10. The chart used to classify stars based on absolute magnitude and temperature is a ______________________________. A. luminosity chart B. main stage chart C. H-R Diagram D. constellation chart

All stars have a life cycle – a beginning and an end. Stars lifespan depends mainly on their initial mass. All stars are formed the same way.

All stars form deep inside a cloud of gas and cosmic dust called a nebula. Gravity causes the densest parts to collapse, forming regions called Protostars. Protostars continue to contract, pulling in surrounding gas, until their cores are hot and dense enough for nuclear fusion to occur.

A star becomes a main- sequence star as soon as it starts fusing hydrogen into helium. It stays a main sequence star until it runs out of hydrogen. Lower mass stars last longer at this phase because they burn fuel at a slower rate then the high mass stars.

Supernovas can only happen when an aging massive star can no longer generate energy from nuclear fusion and undergoes a rapid gravitational collapse. This collapse releases potential energy that heats up and throws off the outer layers of the star in the form of an enormous explosion. Higher Mass Star composition and fusion levels

Galaxies are huge collections of stars. The universe contains hundreds of billions of galaxies.

Origin and Expansion of the Universe

Doppler Shift Dark Energy The shift to a different wavelength that shows how light travels either towards or away from the observer. Dark energy is a mysterious repulsive force that causes the universe to expand at an increasing rate.