Astronomical distances

1. Astronomical distances • Astronomers have developed units other than kilometers or meters to measure the vast distances in space. • One light year is equal to the distance that light travels through space in one year.

2. Determining distances to closer objects in the universe • Astronomers use a method called parallaxto determine the distance of stars that are closer than 1,000 light years to Earth. • As Earth revolves around the Sun, the nearby stars appear to change positions in the sky over the course of one year.

3. Determining distances to closer objects in the universe • To use parallax, astronomers determine the position of a closer star (moving) in relation to faraway stars (not moving). • Next, they look at the same star six months later, and measure its change in position relative to the distant stars.

4. Telescopes • Telescopes work by collecting the light from a distant object with a lens or mirror and bringing that light into a concentrated point, called the focal point.

5. Telescopes • A refracting telescopeuses lenses to bend, or refract, light, making objects look bigger. • Refracting telescopes are made from a long tube, a glass objective lensthat you point toward the sky, and an eyepiece lens.

6. Telescopes • A reflecting telescopeuses mirrors instead of lenses to gather and focus light. • A concave mirror (called the primary mirror) is placed at the back of a tube. • Thesecondary mirror deflects the light to an eyepiece lens.

7. Telescopes and electromagnetic waves • Astronomers use different types of telescopes to view the different types of waves emitted by objects in space. • A radio telescopeworks like an extremely powerful receiver that picks up radio waves from space. • Infrared telescopesare often placed on satellites that orbit above Earth. • X-ray telescopesare designed to detect high-energy radiation (X-rays) from space.

8. Telescopes and electromagnetic waves • These images of the Crab Nebula were taken with different telescopes. • Each new view gave astronomers more information.

9. Satellites and other space craft • The Hubble Space Telescope is a satellite that orbits Earth out of reach of “light pollution.” • It sends images from deep space to computers back on Earth.

10. Spacecraft • NASA’s Mars Exploration Rover (MER) Mission began in 2003. • Two unmanned rovers, Spirit and Opportunity, were sent to explore the surface features and geology of Mars. Two generations of Mars Rovers: Sojourner and Spirit

11. Spacecraft • NASA’s Phoenix lander launched in August 2007. • The lander contains a robotic arm that digs through the Martian soil and brings samples onboard for scientific analysis.

12. Galaxies • A galaxyis a huge group of stars, dust, gas, and other objects bound together by gravitational forces. • The sun, along with an estimated 200 billion other stars, belongs to the Milky Way galaxy.

13. Types of galaxies • The Milky Way is a flattened, rotating system that contains young to middle-aged stars, along with gas and dust. • Astronomers identify it as a spiral galaxy.

14. Types of Galaxies Astronomers classify galaxies according to their shape. • Spiral galaxies consist of a central, dense area surrounded by spiraling arms. • Barred spiral galaxies have a bar-shaped structure in the center. • Elliptical galaxieslook like the central portion of a spiral galaxy without the arms. • Lenticular galaxiesare lens-shaped.

15. The central black hole theory • Recent studies have suggested that a black hole, with a mass of more than a million Suns, exists at the very center of our galaxy. • The evidence for a huge black hole comes from measurements of the orbital velocities of stars and gas at the center. • One of the strangest predictions of Einstein’s theory of relativity is the existence of black holes.

16. The central black hole theory • The minimum speed an unpowered projectile must have to escape the planet’s gravity is called the escape velocity. • A black hole is an object with such strong gravity that its escape velocity equals or exceeds the speed of light.

17. Distances between galaxies • The distances between stars are 10,000 times greater than the distances between planets. • The distances between galaxies are a million times greater than the distances between stars.

18. Doppler Shift • Doppler shift also occurs with electromagnetic waves, such as visible light, X-rays, and microwaves. • This phenomenon is an important tool used by astronomers to study the motion of objects in space.

19. The expanding universe • Edwin Hubble discovered that the farther away a galaxy was, the faster it was moving away from Earth. • This concept came to be known as the expanding universe.

20. The Big Bang theory • The theory that the universe was expanding implies the universe must have been smaller in the past than it is today. • It implies that the universe must have had a beginning. • Astronomers today believe the universe exploded outward from a single point. • This idea is known as the Big Bang theory.

21. The Big Bang theory • The Big Bang theory says the universe began as a huge explosion between 10 billion and 20 billion years ago. • According to this theory, all matter and energy started in a space smaller than the nucleus of an atom.

22. Evidence for the Big Bang theory • In the 1960s, Arno Penzias and Robert Wilson were trying to measure electromagnetic waves given off by the Milky Way. • The “noise” these scientists found was the cosmic microwave background radiation predicted by the Big Bang theory.

23. Evidence for the Big Bang theory • The proportion of hydrogen to helium is consistent with the physics of the Big Bang. • If the universe were significantly older, there would be more heavy elements present compared with hydrogen and helium.

24. Planetary systems • A star with orbiting planets is called a planetary system. • Scientists now believe that planets are a natural by-product of the formation of stars.

25. How the solar system formed • Scientists think that the solar system was formed out of the same nebula that created the Sun.

26. STARS AND GALAXIESThe Life Cycle of a Star: Stars have a life cycle and evolve over time. The mass of a star controls itsEvolutionLifespan Ultimate fate (how it dies) Our Sun: an average size star:

28. Stars begin as a nebula (cloud of gas and dust) that starts to contract due to gravity. Protostar: temperature increases, millions of years later the gas becomes plasma and fusion begins. Main sequence star: (the longest stage in the life of a star) nuclear fusion (hydrogen fuses into helium) continues in the core of the star...our Sun is a main sequence star. Balancing Act

29. Stars more massive than our Sun may be main sequence stars for only 10 million years • Stars less massive than our Sun may be main sequence stars for 100’s of billions of years • Remember: the larger the star the shorter the life span, the smaller the star the longer the life span

30. A star starts to die when hydrogen runs low: Giant: A star cools as it expands and starts to glow red. Giants can be more than 10 times larger than the sun. White dwarf: outer layers escape into space, the star collapses into a dense hot, dim star smaller than Earth. Path of a star much larger than our sun Path of our Sun

33. Massive Stars die explosively!! Supergiant: Massive stars become larger than giants as they leave the main sequence….they can be 100 to 1,000 times larger than the sun. Supernova: the explosion of a supergiant • Neutron Star: a small dense ball of neutrons that spin after a supernova explosion • Black Hole: the remnants of a supernova that are contracted even more than a neutron star… it is so dense light cannot escape from it.

34. Are Black Holes Important? Every spiral galaxy, like our own Milky Way, is thought to have a supermassive black hole at its center. The black hole at the center of the Milky Way is sort of like the Sun at the center of our solar system - the galaxy orbits the black holes like the planets in solar systems orbit the stars. ultraviolet-light exposure

35. Massive Stars are important because….. During the fusion process of hotter massive stars, elements such as iron, oxygen, silicon and magnesium are created. These are elements needed for life. Composition of Universe

36. Magnitude describes the brightness of a star • Two types of brightness: absolute magnitude and apparent magnitude • Apparent magnitude is the brightness we see here on Earth • Absolute magnitude is the actual brightnessthe star gives off. The more negativethe number, the brighter the star is!

37. ORION CONSTELLATION Betelgeuse Rigel Rigel

38. To figure out how far it is to a star, astronomers look at it from two different positions, called parallax Parallax is a method used to determine distance to a star.

39. STARS ARE CLASSIFIED BY THEIR SIZE, COLOR AND TEMPERATURE • Not all stars are the same colorbecause different elements burn different colors. Some are red, some are blue, etc. • Color tells the temperature of the star • Hotstars are bluish/white andcoolerstars are reddish/orange • Astronomers call this a star’s spectral class. Spectral classes are O, B, A, F, G, K, and M Flame Test Clip

40. O, B, A, F, G, K, and M... (Oh Be AFine Guy Kiss Me) and for you guys: Oh Be A Fine Girl Kiss Me!!

41. Hertzsprung-Russell Diagram (H-R Diagram) • Stars are ranked on the H-R Diagrambased on their temperature and absolute magnitude • Most stars fall in the middle of the diagram, called the main sequence • Very few stars are white dwarfsor giants/supergiants

42. H-R Diagram---shows the life cycle of stars supergiants Main sequence giants Absolute magnitude White dwarfs temperature

43. THE 3 TYPES OF GALAXIES • Our galaxy, the Milky Wayis part of a larger group of galaxies called the Local Group • There are about 30galaxies included in the Local Group There are three types:elliptical, spiral, and irregular • Our galaxy the Milky Way is a spiral galaxy The Andromeda galaxy is an example of a spiral galaxy with huge spiral arms. Astronomers believe the Milky Way resembles this.

44. Elliptical can be football-shaped 2. Elliptical galaxies are the most common 3. Irregular are all the galaxies that are NOT spiral or elliptical, and are not nearly as common Irregular

45. Where Are We in Our Galaxy?

46. Earth, Moon & Sun Relationship

47. Earth and Sun Relationship • Earth completes one revolution around the sun every 365 ¼ days. • Revolution – the time it takes for the Earth to complete 1 orbit around the sun.

48. What is Rotation? • Rotation – the Earth rotates around its axis once every 24 hours. • This is what causes night and day!

49. What Causes the Seasons? • Due to its axial tilt, Earth experiences seasons during its revolution around the sun.

50. Earth and Moon Relationship • The moon revolves around the Earth about once every month.