1. Astronomy

2. Astronomy Vocabulary Big Bang Theory: the tremendously powerful explosion of an incredibly dense mass about 15-20 billion years ago that produced the expanding universe that exists today. Celestial object: something in space, such as a star or planet. Constellation: stars that appear to be grouped in patterns forming the outlines of people, animals, and physical objects in the sky. Doppler effect: the apparent change in wave frequency as an energy source moves toward or away from the observer. Galaxy: a system of billions of stars. Luminosity: relative brightness of something. Polaris: the North Star, which is located almost directly above Earth’s geographic North Pole. Red shift: as a source of visible light moves away from the observer, the wavelengths increase, creating a shift toward the red end of the visible spectrum. Star: a fixed luminous point in the night sky that is a large, remote incandescent body like the sun. Solar System: includes our Sun, the nine planets, and many Moons, and all the other objects that revolve around the Sun. Universe: all existing matter and space considered as a whole; the cosmos.

3. The Universe The universe is everything! –All matter, time, energy, and space is part of the universe. How old do scientists believe the universe is? –10-15 billion years old (Earth is 4.6 billion years old) Where do we think the universe came from/how did it form? –The Big Bang Theory : 1.The universe started as a single point where all matter and energy were condensed 2.That point was extremely dense 3.This point became unstable and there was an outward explosion 4.All matter and energy spread away from that point and continues to move away from the center of the universe today

4. Proof of the Big Bang Theory What proof do we have? –The Doppler Effect - shows us a change in wavelength as the distance between two objects increases or decreases Red Shift – when an object is moving away from us the wavelength increases, or gets longer. Think about two people holding a slinky between them and walking away from each other – THE WAVELENGTH INCREASES (stretches out) Blue Shift – when an object is moving towards us the wavelength decreases, or gets shorter. Think about two people holding a slinky between them and walking towards each other – THE WAVELENGTH DECREASES (pushed closer) –Now apply this to the visible light portion of the Electromagnetic Spectrum (p. 14 ESRT). This shows red on the increasing wavelength side and blue on the decreasing wavelength side. Label your diagrams with “red” and “blue” – Normal energy pattern – Red shift – same energy pattern as normal, moved to – the red side of spectrum - this is from an object – moving away from us – Blue shift – same pattern as normal, moved to the – blue/violet side of the spectrum, this is from an object – moving towards us

5. Size Classification Put these objects in increasing order: –galaxy, solar system, star, universe Universe galaxy solar system star planet moon __________________________________________________________________________ largest smallest Galaxy – a group of millions of stars held together by gravity –Ex: Our sun is part of the Milky Way Galaxy. It is a spiral shaped galaxy. top view side view (profile)

6. p. 15 ESRT Characteristics of Stars What variables are used on the y-axis to classify stars? –Luminosity (brightness compared to the sun, assuming an equal distance) –Size (small to massive) What variables are used on the x-axis to classify stars? –Color (blue on the left to red on the right) –Temperature (hotter on the left to cooler on the right, in °K) What are the different categories of stars? –Supergiants –Giants –Main Sequence –White Dwarfs Label each group with it’s life stage –Main Sequence – Early Stage –Supergiants – Intermediate Stage –Giants – Intermediate Stage –White Dwarfs – Late Stage

7. ESRT Practice Draw a line horizontally through the sun across the entire chart. Stars above this line are more luminous (brighter) and more massive than the sun. Stars below this line are less luminous and less massive. Draw a line vertically through the sun across the entire chart. Stars to the right of this line are cooler than the sun and stars to left of this line are hotter. What type of star is the sun? –Main Sequence Which has a higher temperature, Barnard’s Star or Sirius? –Sirius Which star is more luminous, Procyon B or Polaris? –Polaris What color is Betelgeuse? –Orange What type of star is Rigel? –A supergiant Which is bigger, Alpha Centauri or the Sun? –Alpha Centauri LOOK at the sun! It is in the middle of the chart. This means that the sun is average in every possible way. It is average in size, temperature, and luminosity.

8. Life Cycle of Stars (Stellar Evolution) Stars form in a nebula (a cloud of dust and gas particles) when gravity pulls enough mass together Stellar evolution (the life cycle of a star) is determined by how massive it is. Look at the diagram → Stars create energy though the process of nuclear fusion. Hydrogen molecules in the star fuse together and create Helium and energy (light and heat). H + H → He + energy