Classifying Stars. Scientists classify stars by: 1. Temperature 2. Brightness

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1 STARS

2 Classifying Stars Scientists classify stars by: 1. Temperature 2. Brightness

3 Star Temperature 1. The color of a star tells us about its temperature. Blue stars are the hottest, 7500 C- 40,000 C. Our sun is yellow in color, in the middle of the temperature scale, from 5000 C C. Red stars are the coolest, less than 3500 C.

4 Betelgeuse- Red Star- Coolest Rigel- Blue Star-Hottest CONSTELLATION ORION

5 Brightness or Magnitude 1. Stars are also classified by their brightness. 2. Apparent Magnitude- The brightness of a star as seen from Earth 3. Absolute Magnitude- The actual brightness of a star.

6 Brightness or Magnitude Example: The SUN has an absolute magnitude of 4.8 when compared to the other stars. The SUN has an apparent magnitude of because it is so close. The lower the number the brighter the star.

7 Another Example of absolute and apparent magnitude. B A Which light is brighter, A or B?

8 Light A is brighter than light B. We see the apparent magnitude of the lights (how they look to us) If lights A and B were next to each other they would look the same because the two lights are exactly the same. Their absolute magnitude is the same. Distance makes them look different. The same is true for stars. Two stars could be the same brightness but their distance from us makes their brightness different.

9 Life Cycle of A Star

10 Life Cycle of A Star Stars are classified as either: 1. Average Stars 2. Massive Stars

11 Life Cycle of Average Stars (Our Sun) 1. Stellar Nebula 2. Protostar 3. Main Sequence 4. Red Giant 5. Planetary Nebula 6. White Dwarf 7. Black Dwarf

12 1. Stellar Nebula 1. All stars begin their lives as clouds of dust and gas called a stellar nebula. 2. Also called Stellar Nurseries

13 2. Protostar 1. Matter in the gas cloud will begin to come together into a dense region called a protostar. 2. As the protostar continues to condense, it heats up.

14 PROTOSTAR

15 3. Main Sequence Stars 1. The longest part of a star s life; heat and light is released 2. The life span of a star depends on its size. 3. Smaller stars (the Sun) will burn for several billion years 4. Our Sun is in its main sequence.

16 Average sized star like our Sun during main sequence. Massive star larger than our Sun during main sequence

17 4. Red Giant and Red Supergiant 1. Eventually, the star's fuel will begin to run out. 2. Our Sun will expand into what is known as a red giant. 3. Massive stars will become red supergiants.

18

19 5. Planetary Nebula Formed when shells of gas or atmosphere thrown out by some stars near the end of their lives

20 Planetary Nebula

21 6. White Dwarfs (Average Star Death) The leftover core of a star Burns as a white dwarf until they cool down. Can shine for billions of years before cooling completely

22 White Dwarf

23 7. Dark Dwarf A dark ball of matter The last phase of an average star s life

24 Life Cycle of a Massive Star 1. Stellar Nebula 2. Protostar 3. Blue Giant 4. Red Supergiant 5. Supernova 6. Neutron Star (Pulsar) OR 7. Black Hole

25 Massive Stars 1 & 2. Same as average star (stellar nebula, protostar 3. Blue Giant- Main sequence of Massive stars. 4. Red Supergiant 5. SUPERNOVA- the star collapses triggering a violent explosion known as a supernova.

26 Massive Stars (Larger than our Sun) Become Red Supergiants.

27 Red Supergiant becomes Supernova in a giant explosion,

28 Massive Stars 6. Neutron Star (Pulsar)- If the remaining mass of the star is about 1.4 times that of our Sun, it will collapse further 7. Black Hole- If the remaining mass of the star is more than three times that of the Sun, it will collapse and what is left behind is an intense region of gravity called a black hole.

29 Supernova Becomes a Neutron Star

30 OR It becomes a Black Hole This is an illustration, not an actual black hole!!

31 Life Cycle of a Massive Star 1. Stellar Nebula 2. Protostar 3. Blue Giant 4. Red Supergiant 5. Supernova 6. Neutron Star (Pulsar) OR 7. Black Hole

32 Types of galaxies spiral has bulge in middle and arms spiral outward; Milky Way elliptical round or flattened balls; contain only old stars irregular no regular shapes; generally bright, young stars quasars active young galaxies with black holes at their centers