1. Astronomy
Earth, Moon, and Sun

2. Days and Years
Astronomy: the study of moon, stars, and other objects in space
Rotation: the spinning of Earth on its axis, this takes 24 hrs
This causes day and night
Revolution: the movement of 1 object around another; 1 revolution = 1 year
Orbit: Earth’s path as it revolves around the sun, its shape is elliptical (egg shaped)

3. Season on Earth
Earth has seasons because its axis is tilted as it moves around the sun
Summer occurs in the hemisphere leaning towards the sun because the sun’s rays are striking it most directly

4. Longest and Shortest Days
Solstice: when the sun is directly over head 23.5° N or S. It is either the longest (summer) or shortest (winter) day of the year
Equinox: (equal night) sun is directly over the equator and day and night are equal

5. Motions of the Moon
The moon revolves around the Earth AND rotates on its own axis every 27.3 days.
This means that a lunar day is the same length as a lunar year!!
As a result, we always see the same side of the moon, that we call the near side

6. Motions of the Moon
The moon’s orbit is an ellipse (egg shape) just like the Earth’s
Perigee – when the moon is closest to Earth
Apogee – when moon is farthest from Earth

7. Motions of the Moon

8. Phases of the Moon
The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth
The lunar cycle, full moon to full moon, is 29.5 days

10. Structure of the Moon The Moon’s diameter is ¼ of the Earth’s
In relation to the planet it orbits, it is the largest moon in our solar system

11. Features of the Moon
Craters: round pits on the moons surface caused by the impacts of meteors

12. Features of the Moon
Maria: dark flat regions on the moons surface that were once lava flows
Highlands: high areas on the moon

13. Eclipses
Lunar Eclipse: when the Earth is directly between the sun and the moon preventing the sunlight from hitting the moon
Solar Eclipse: when the moon is between the sun and the Earth preventing the sunlight from hitting Earth
Occurs at full moon
Occurs at new moon

14. Eclipses Umbra – the darkest part of a shadow
Penumbra – the larger part of the shadow surrounding the darkest part
Solar eclipse
Lunar Eclipse

15. Tides Tides: the rise and fall of water level in the oceans
What causes tides?
Tides are a result of differences in how much the moon’s gravity pulls on different parts of the Earth

16. Types of Tides
There are 2 high tides and 2 low tides each day (25 hour cycle)
Neap Tide: smallest tide, least difference between high and low tide.
Moon phase first and last quarters.
Spring Tide: when there is the greatest difference between high and low tide.
When moon is in new or full phase

17. Tides

18. Origin of the Moon
Collision theory: AKA – Giant Impact Theory - states that the moon formed when an object from space collided with Earth, throwing large chunks of Earth into space which then condensed to form the moon

19. Satellites
Satellite: any natural or artificial object that revolves around an object in space.
Is the moon a satellite?
YES!
Geosynchronous: they revolve around earth at the same rate earth rotates, so they stay over the same place

20. Chapter 2 The Solar System

21. Observing the Solar System
Geocentric: the theory that the Earth is the center of the solar system, supported by Ptolemy (Greek astronomer) WRONG!

22. Observing the Solar System
Copernicus
Galileo
Heliocentric: theory that the Sun is the center of the solar system proposed by Copernicus and proved by Galileo (who was subsequently put under house arrest)

23. Observing the Solar System
Johannes Kepler (German mathematician) analyzed Tycho Brahe’s (Danish astronomer) planetary observations and calculated that planet’s orbits are elliptical
Brahe
Kepler

24. Observing the Solar System
Isaac Newton concluded that inertia and gravity combine to keep planets in orbit.

25. Observing the Solar System
Inertia: the tendency of a moving object to keep moving in a straight line or a stationary object to remain in place.
Gravity: the attractive force between 2 objects; depends on the masses and distance between the 2 objects

26. Rockets
Newton’s 3rd Law: For every action there is an equal and opposite reaction
This law demonstrates how rockets are launched into space

27. The Sun’s interior
The sun’s interior is like a giant furnace producing energy through nuclear fusion
nuclear fusion: the process of combining 2 hydrogen nuclei fusing to form helium
Nuclear fusion occurs in the sun’s core where the temperature is 15 million degrees Celsius
NASA - The Composition of the Sun

29. The Sun’s Atmosphere The sun’s atmosphere has 3 layers:
Photosphere: inner layer of the sun’s atmosphere where light is produced and what we see when we look at the sun
Chromosphere: middle layer of the sun’s atmosphere
Corona: outer layer of sun’s atmosphere only visible during solar eclipses

31. Features of the Sun
Solar wind: stream of electrically charged particles sent out from the corona, causes the aurora borealis
Sunspot: areas of gas on the sun’s surface that are cooler than the surrounding areas

32. Sunspots

33. Features of the Sun
Prominence: reddish loops of gas that link different areas of sunspots

34. Features of the Sun
Solar flares: an explosion of hydrogen gas that results when prominences connect
Solar flares video

35. Mercury Closest to sun No moons No atmosphere Sky is black
450°C during the day and -170°C at night
Image:

36. Venus Similar in size to Earth Revolution (1 yr) = 7.5 months
Rotation (1 day) = 8 months
Rotation is retrograde which means it rotates in the opposite direction or from east to west

37. Venus
Atmosphere is thick and full of carbon dioxide resulting in a strong greenhouse effect
As a result Venus is actually hotter than Mercury, its surface is 460°C, hot enough to melt lead!
Surface of Venus

38. Mars The red planet Thin atmosphere is mostly carbon dioxide
Has an ice cap at its north pole
Has a tilted axis like Earth so it has season
It has 2 moons: Phobos and Deimos

39. The Outer Planets
Jupiter, Saturn, Uranus, and Neptune are known as the “gas giants” because they are much larger than Earth and do not have solid surfaces.
The composition of their extremely thick atmospheres is similar to the gases in the sun
Astronomers think they may have solid cores made of rock, ice, and frozen carbon dioxide

40. Jupiter
Largest planet
Thick atmosphere made of hydrogen and helium

41. Jupiter Has the Great Red Spot, a hurricane like storm
Has 50 confirmed moons & 17 provisional ones
Moons: Io, Ganymede, Callisto, and Europa
Jupiter and its moon Io

42. Saturn 2nd largest planet Has very large rings made of dust and ice
Has 53 satellites including Titan which has an atmosphere

43. Saturn Saturn orbits the sun once every 29 years
Its winds blow up to 1600 ft/s

44. Uranus Twice as far from the sun as Saturn
Discovered by William Herschel in 1781
It takes 84 Earth years for it to orbit the sun
It has 27 moons
Farthest planet that can be seen without a telescope

45. Uranus Looks bluish because of the traces of methane in its atmosphere
Its axis is tilted 90° from vertical so it rotates from top to bottom

46. Neptune Featureless blue atmosphere with some visible clouds
30x farther from the sun than Earth
165 Earth years to orbit the sun

47. Neptune
It has several rings 13 moons including Triton, which is the only 1 known to orbit in the opposite direction as its planet

48. Dwarf Planet - Pluto
discovered in 1930 and long considered to be the ninth planet
From 1979 to 1999, Pluto was actually closer to the Sun than Neptune

49. Dwarf Planet - Pluto
May be the largest of icy objects just beyond Neptune called the Kuiper Belt
Has 5 moons

50. Comets
Comets: chunks of ice and dust whose orbits are usually long narrow ellipses
Comets get their name from the Greek word "kometes" (long hair)

51. Asteroids
Largest space rocks that revolve around the sun that are too small and too numerous to be considered planets

52. Asteroids Asteroids are made up of rock and iron
Most are found between Mars and Jupiter in the Asteroid Belt

53. Meteoroid
a chunk of rock or dust in space that usually come from comets or asteroids
Meteoroids orbit our Sun just like asteroids and planets

54. Meteorite
a meteoroid that passes through Earth's atmosphere and hits Earth's surface

55. Meteor
A meteoroid that enters Earth's atmosphere and burns up

56. Stars, Galaxies, and the Universe

57. Tools of Modern Astronomy
Electromagnetic Radiation: a form of energy (including light) that can travel through space in waves
Visible light: light we can see with our eyes (ROYGBIV = spectrum, or colors, of visible light)
Longest wavelengths:radio, infrared waves
Shortest: Ultra violet, x-rays, gamma rays

58. Tools of Modern Astronomy
Visible Light Telescopes: produce images using visible light
Refracting Telescopes: Uses convex lenses to gather and focus light
Reflecting Telescopes: uses 1 or more mirrors to gather light
Radio Telescope: a device used to detect radio waves (electromagnetic radiation) in space
Others use infrared radiation, UV rays, x-rays, and gamma rays

59. Tools of Modern Astronomy
Observatory: a building that contains 1 or more telescope
Constellation: patterns of stars in the sky
Satellites: Telescopes are placed on satellites because most electromagnetic radiation is blocked by our atmosphere
Hubble space telescope

60. Tools of Modern Astronomy
Spectrograph: breaks light from an object into colors and photographs the resulting spectrum
Astronomers use spectrographs to get info about stars including their chemical composition and temperatures

61. Characteristics of Stars
Universe: all space and everything in it
Galaxy: A giant structure that contains hundreds of billions of stars
Light year: the distance that light travels in 1 year = 9.5 trillion Km
(light speed = 300,000 Km/s)

62. Characteristics of Stars
Parallax: is the apparent change in the position of an object when you look at it from different places.
Astronomers use parallax to measure distance to nearby stars

63. Characteristics of Stars
The main characteristics used to classify stars are:
size
temperature
brightness

64. Characteristics of Stars
A stars color reveals its temperature
blue stars are the hottest and red the coolest
How bright a star looks from earth depends on 2 things:
how far it is from earth
how bright it actually is

65. Characteristics of Stars
Apparent magnitude: a stars brightness as seen from Earth (how bright it appears to be)
Absolute Magnitude: the actual brightness of a star

66. Characteristics of Stars
Hertzsprung-Russell Diagram: a graph relating the temperature and brightness of stars
Main sequence stars: 90% of all stars, where as surface temperature increases brightness increase (like our sun)

68. Birth of Stars
Stars begin life in a nebula

69. Birth of Stars
As gravity pulls the gas and dust of the nebula together a protostar is formed
A star begins life when it is hot enough that nuclear fusion begins
**How long a star lives depends on how much mass it has; small stars burn their fuel more slowly than large stars

70. Deaths of stars
When a star runs out of fuel it becomes a white dwarf, a neutron star, or a black hole
White dwarf: small and medium stars become red giants and then when they run out of fuel become white dwarfs, when it stops glowing it is dead and is called a black dwarf

71. White dwarf

72. Deaths of stars
Neutron star: a giant or super giant star can explode causing a supernova
The material that is left over from the explosion becomes a neutron star which are smaller and denser than white dwarf
podcast

73. Deaths of stars
Black Hole: the remains of the most massive stars collapse into black holes

74. Star Systems and Galaxies
More than half of stars are members of groups of 2 or more stars called star systems
Binary stars: stars systems with 2 stars (75% of all stars)
Eclipsing binary: a star system in which one star periodically blocks the light from another

75. Star Systems and Galaxies
Planets around other stars
51 Pegasi was the 1st found
So far we have only been able to detect very large planets
- “Goldilocks conditions” – Conditions (size, distance from the sun etc.) that are “just right” to support life or for life to evolve

76. Star Systems and Galaxies
4 main types of galaxies:
Spiral: these have arms that radiate outward like pinwheels (milky way)
Elliptical: these look like flattened balls, contain billions of stars, and have little gas and dust between the stars
Irregular: galaxies without a regular shape
Lenticular – smooth disc galaxies of older stars, they have used up the material between the stars

77. History of the Universe
Big bang: the initial explosion that resulted in the formation and expansion of the universe
According to this theory, the universe formed billion years ago
The universe is always expanding: Edwin Hubble discovered that the galaxies are moving away from each other
Our solar system and sun were formed about 5 billion years ago