2. Chapter 19 The Universe Beyond Chapter 15 The Universe

3. Types of stars Color and temperature of stars both depend on the size of the star. Bigger stars are hotter. Smaller stars are cooler. Colors of stars ColorSurface Temp. 0 C Blue (30,000+) Blue-White (10,000-30,000) White (7,500-10,000) Yellow (5,000-7,500) Orange (3,500-5,000) Red (< 3,500) OBBAAGGKKMMOBBAAGGKKMMBAGKM

4. Spectrum –S–Scientists can analyze the light coming from stars to determine the types of elements present in the star –B–Black lines indicate the light absorbed by specific elements in the star

5. Apparent magnitude How bright a star appears to be from Earth –Our sun appears to be the brightest star in the sky because it is the closest ( -26.8 on the apparent mag. scale)

6. Absolute magnitude How bright a star actually is, as if all stars were the same distance away –Our sun is only average compared to other stars (+4.8 on the absolute mag. scale). 1234512345

7. Parallax Scientist use a method called parallax to calculate the distance of stars. Earth in January Earth in July sun Very distant stars Closer stars seem to move more

8. Parallax causes nearer stars to appear to move more over the course of the year.

9. Constellations are used as maps to help guide our way as we look at the stars above. The names and “pictures” they appear to form come from stories from many cultures. Canis Major (The big dog) –Sirius, one of the brightest stars in or night sky, is called the Dog Star, and the hot summer season is called the dog days since Canis Major rises at the height of summer. Cassiopeia (The Vain Queen) –Found near the celestial north pole. –In the Greek legend she bragged about her beauty and was punished by the sea god, Poseidon, who placed her in the sky.

10. Cygnus (The Swan) –In the Greek legend Zeus disguised himself as a swan from time to time. –Its brightest star, Deneb is one of the brightest stars in the sky –Seen in the summer night sky. Orion (The hunter) –Easily identifiable by the three stars of his belt during the fall and winter –Betelgeuse, the hunter’s right shoulder, is a red supergiant star. If it was in our sun’s place it would extend to the orbit of Jupiter. It will explode in a supernova explosion sometime in the next 1000 years. When this happens it will be brighter than the full moon and even visible during the day for weeks. –There are several interesting objects located around this constellation.

11. The distance between stars is measured in light years ( the distance light travels in one year) because they are so far apart. –The next nearest star to our sun is 4 light years ( nearly 38.7 trillion kilometers away or 252,000 A.U.) 10,000 light years

12. Section 2 The Life Cycle of Stars

13. Red dwarves Smallest, coolest, dimmest stars –Less than 1 solar mass Last the longest, 100 billion years Although they are less visible than the brighter blue and white stars, 2/3 of the 370 stars closest to Earth are red dwarf stars. The closest star after our sun is Proxima Centauri, a red dwarf seen from the southern hemisphere. Proxima centauri is our closest neighbor star after the sun.

14. Yellow stars Like our sun, medium size and temperature –Around 1 solar mass Last for 10 billion years

15. Blue/White Giants Largest, hottest, brightest stars –5 solar masses or more Shortest lasting stars, maybe only 10 million years Sirius

16. Red Giants/ Supergiants Dying stars that are running out of fuel These stars (former red, yellow and blue stars) have swollen up due to internal pressure, their surfaces have cooled Betelgeuse

18. White dwarves Small, shrunken stars that no longer have fusion happening. They glow only due to the high temperature of their cores, heat gathered from when they burned their fuel. They become black dwarves when they cool enough to stop glowing.

19. caSmall stars lead quiet, calm lives and have quiet, calm endings ar ntLarge stars lead short, violent lives and have violent endings eatu How a star dies depends on its size and temperature

20. 4 3 2 1 Small stars (smaller than our sun) 1. Red dwarves live as long as 100 billion years before using up all of their hydrogen fuel. 2. They will swell into red giants, many times larger than it was before. 3. When the fusion process fails gravity causes the star to shrink into a white dwarf ( about the size of its core), which will slowly cool into a black dwarf.

21. 2 1 Medium Stars ( like our sun) 1. Yellow stars like our sun will be able to continue the fusion process for 10 billion years. 2. As the fuel runs out they will swell into red giants. Sometimes the star may shrink and swell repeatedly, called a variable star.

22. 5 4 3 3. These red giants may blow off their outer layers as rings of gases, called planetary nebula, as the last of its fuel is spent. 4. When the fusion process fails gravity causes the star to shrink into a white dwarf ( about the size of its core), which will slowly cool into a black dwarf.

23. 2 1 Massive Stars (several times larger than our sun) 1. White and blue giants burn up their fuel in as little as 10 million years. 2. These stars swell into red supergiants, some as big as our entire solar system.

24. 3 3. These may shrink and swell before they finally explode in a massive supernova explosion. a. Supernovas create all of the larger elements in one instant. b. Supernovas are as bright as the entire galaxy for a short time before they begin to fade. c. The outer layers are blown outward, the inner layers are blown inward creating super-dense cores called neutron stars, which are only 20-100 km across, but are still heavier than our sun.

26. 4 d.A spinning neutron star is called a pulsar because the beam of energy from the pole sounds like a pulse on Earth. e.A very large star creates a very small neutron star, called a black hole. *Black holes are at least three times more massive than our sun but less than 10 km across

27. A black hole is the core of an exploded star. The material is so dense that the speed needed to escape it is faster than the speed of light. This means that any object that gets too close would not be able to escape. The existence of black holes was first proposed by Albert Einstein as a result of his Theory of General Relativity. He called them “dark stars”, but suggested these monsters could not possibly exist for real. They have been observed due to the effect of their massive amounts of gravity on surrounding objects

28. Hertzsprung-Russell Diagram H-R Diagram is a chart comparing a star’s brightness (luminosity) to its surface temperature. BRIGHTNESS SURFACE TEMPERATURE White Dwarves dim bright hotcool Blue Giants Red Dwarves Red Giants and Supergiants MAIN SEQUENCE STARS Main Sequence stars are normal “adult” stars not in the process of dying NORMAL ADULT STARS NORMAL ADULT STARS NORMAL ADULT STARS (LUMINOCITY)

29. BRIGHTNESS SURFACE TEMPERATURE 10 -4 20,000 0 3,000 0 Sol Sirius NameBrightnessSurface Temperature ( 0 C) Type Sol4.85840Main Sequence VanMaanen’s14.213,000White Dwarf Sirius-5.125,500Blue Giant Proxima Centauri 10.33,200Red Dwarf Betelgeuse-5.73,200 Red Giant (supergiant) vanMaanen’s Star Betelgeuse Proxima Centauri 3,500 0 10,000 0 6,000 0 5,000 0 7 4 2 0 -2 These are main sequence stars too

32. Section 3Galaxies

33. Types of Galaxies Spiral galaxies have a central bulge and distinctive spiral arms Our home galaxy, the Milky Way, is an example Formed slowly, giving time for gravity to create the spiral structure Barred SpiralSpiral

34. Elliptical galaxies are spherically shaped and have been cleaned out of nebula, which means few new stars are forming Form quickly, before gravity has a chance to change the shape

35. Irregular galaxies do not fit the other categories These are small galaxies being distorted by gravity from other nearby galaxies Large Magellanic Cloud (LMC) – a neighbor to our Milky Way Galaxy (a satellite to our galaxy). It was seen by Ferdenand Magellan as he circled the world. It can only be seen from the southern hemisphere.

36. Galaxies have several parts o Each star is its own solar system (containing planets and other objects) o Nebula (gas and dust clouds where new stars form), seen as dark lines.

37. Active galaxy centers –S–Supermassive black holes are thought to be at the center of most galaxies. Contain millions of solar masses Quasars are very distant objects only visible because they emit huge amounts of energy. These are massive blackholes eating material. Quasars are the brightest objects in the universe and are used to measure the size of the universe.

39. The Big Bang Theory The Big Bang Theory describes the formation of the universe resulting from a massive explosion of a single object which generated all matter and energy that currently exists in the universe. This model explains the observations being made and has been confirmed by huge amounts of data. Working backwards scientists have determined that the Big Bang Event occurred 14 billion years ago. While new evidence and observations all continue to confirm this theory, new discoveries seem to indicate that the universe is accelerating as it expands. This was not expected and is difficult to explain.