Light Years, Important People, Galaxies

1. Light Years, Important People, Galaxies 8th Grade

2. Standard 8.E.4: The student will demonstrate an understanding of the universe and the predictable patterns caused by Earth’s movement in the solar system. • 8.E.4A.1: Obtain and communicate information to model the position of the Sun in the universe, the shapes and composition of galaxies, and the measurement unit needed to identify star and galaxy locations

3. Milky Way Galaxy • The Sun is a star in the Milky Way galaxy located in a spiral arm about two-thirds of the way from the center of the galaxy.

7. Galaxy Reminder • The sun is a star in the Milky Way galaxy. • The sun and its planets are located about 2/3 of the way from the center of the galaxy

8. WHAT IS A GALAXY? • Galaxies are made up of gas, dust, and billions of stars held together by gravity, and have different shapes.

9. How big are galaxies? The largest galaxies have more than a TRILLION stars. There are BILLIONSof galaxies in the universe.

10. Galaxy Shapes • Galaxies have 3basic shapes

11. 3 Types of Galaxies As you look at this image, you will notice many different types of galaxies. Edwin Hubble, the astronomer for whom the Hubble Space Telescope is named, began to classify galaxies in the 1920s, mostly by their shapes. We still use the galaxy names that Hubble originally assigned.

13. Spiral Galaxies A nucleus of bright stars and two or more spiral arms Spiral galaxies appear to have a bulge in the middle and arms that spiral outward, like pinwheels. The spiral arms contain many bright, young stars as well as dust and gas. Relatively few new stars are forming in the central bulge. The milky way is a spiral galaxy

14. The Milky Way

15. Elliptical Galaxies Spherical or flattened discs About one third of all galaxies are simply massive blobs of stars. Elliptical galaxies have very bright centers and very little dust and gas. Because there is so little gas, there are no new stars forming, and therefore elliptical galaxies contain only old stars.

16. Irregular Galaxies NO DEFINITE SHAPE When Hubble first classified galaxies, he had a group of leftovers. He named them “irregulars.” Irregular galaxies are galaxies that do not fit into any other class. As their name suggests, their shape is irregular.

17. Can you find examples of spiral, elliptical, and irregular galaxies?

18. Guess the Galaxy

20. Light Years • Because distances in space are so great that conventional numbers are too large to work with, astronomers use a unit of measurement called light year to measure the distance to stars and galaxies in space. The distance in one light year is equal to the distance light travels in one year. • Crazy Fact: The milky way galaxy is 150,000 light years across it’s middle • Our Neighbor: The closest galaxy to us, the Andromeda Galaxy, is 2.5 million light-years away

21. What is a Light Year? • Light Years is a measure of distance, not time. It is the total distance that a beam of light, moving in a straight line, travels in one year. • Light travels 9.46 x 1012 km (5.88 x 1012 miles) in a year. This means that the light that we are seeing from objects in the sky is from the past.

22. How old is the light? • Light from the sun takes 8 minutes to travel from the sun to Earth • The light from the nearest large galaxy, Andromeda, was emitted 2.5 million years ago. Therefore, the images we see of these objects are how they looked at the time in the past when their light left them. • The further away an object is, the older the light is that we are receiving from it.

23. Collisions • The shapes of galaxies can change over time as a result of various factors including collisions with other galaxies and the evolution of the galaxy itself.

24. The sun is about 150,000,000 km away from earth. Why is the light from the sun about 8 minutes old when it reaches your eye?

25. If the North Star is 360 light years away, it takes 360 years for its light to reach earth. If it is now 2014, the light from the North Star we see now is from the year 1654.

26. Important Astronmers(a.k.a. old dudes with beards)

27. Astronomers • There are multiple historical figures that have contributed to our current understanding of the Sun’s location in the Milky Way. The following are included: • o Johannes Kepler • o Galileo Galilei • o Tycho Brahe

28. Galileo Galilee • Father of modern astronomy • Improved the telescope • Proved heliocentric model of the universe (sun is the center, not the earth)

29. Johannes Kepler • Proposed elliptical orbit of planets around the sun • Also said earth revolves around the sun, not the other way around

30. Edwin Hubble • Classified galaxies by their shape • He is who the Hubble Space Telescope (a REALLY powerful telescope used by NASA) is named after!

31. What is a Parallax? • Astronomers use a method called parallax to determine how far away stars are. Parallax is a method that astronomers used to determine how far away stars are. Stars seem to shift their position when viewed from Earth because of Earth’s revolution about the Sun. This is referred to as a parallax shift. Astronomers use the diameter of Earth’s orbit to determine the parallax angle across the sky.

32. Why the controversy? • Both men got in trouble for saying that the earth revolved around the sun! • At the time, many people thought the earth was the center of the universe

33. TOMORROW The CREATION and EXPANSION of the Universe!