Astronomy Earth and Moon Solar System Stars and Galaxies

Effects of Gravity Gravity – force of attraction between any two objects Mass – amount of matter that an object contains Orbit – curved path that an object follows as it revolves around another object

Earth’s Movement Revolution – movement of one object in its orbit around another object; a single revolution takes about 365 days The various positions of the Earth in relation to the Sun will cause seasons in some parts of the world Solstices – Sun is directly on the Tropic of Cancer or Tropic of Capricorn Equinoxes – Sun is directly on the Equator

Moon’s Movement Revolves completely around the Earth in about 29 days Rotates on it’s axis about once every 29 days Therefore, we always see the same side of the Moon Phase – change in the Moon’s appearance as it orbits the Earth 4 main phases: New, First Quarter, Full, Third Quarter

Eclipses Lunar eclipse – passing of the Moon through the Earth’s shadow; Earth is between the Sun and the Moon Solar eclipse – passing of the Moon between the Earth and the Sun; Moon casts a shadow on the Earth

Solar Eclipse

Lunar Eclipse

Tides Tides – regular rising and falling of the Earth’s major bodies of water Moon’s gravity causes ocean water to pile up on the side of the Earth facing the Moon Other factors that affect tides are wind, ocean temperature, and water flowing into the ocean

Moon’s Surface Maria – low, flat plains on the Moon’s surface that appear as dark areas Crater – circular low area surrounded by a rim, usually caused by an object hitting the ground Apollo Missions: Between 1969 and 1972, seven trips to the Moon. –Measure moonquakes, moon rocks and dust, approximately 4.6 billion years old –No other people have visited the Moon since.

The Solar System Star – glowing ball of hot gas that makes its own energy and light Planet – large object in space that orbits a star, such as the Sun Moon – natural satellite that orbits a planet Solar system – a star, such as the Sun, and all of the objects that revolve around it in space.

The Solar System

The Sun Made of hydrogen (H) and helium (He) Rotates on an axis; parts rotate at different rates Temperature: Outer 5,500 °C, Inner 15,000,000 °C. Nuclear reactions fuse two hydrogen atoms to make one helium atom

Parts of the Sun Atmosphere – envelope of gas surrounding an object in space Photosphere – inner layer of the Sun’s atmosphere that gives off light Chromosphere - middle layer of the Sun’s atmosphere that can be seen during an eclipse; has a distinctive red color Corona – outer layer of the Sun’s atmosphere Sunspots – cooler areas of the Sun that give off less energy

The Inner Planets Inner planets: Mercury, Venus, Earth, Mars; closest to the Sun All are solid and have a high density Similar in size and have a low mass Rocky

Mercury Closest to the Sun Fastest moving; revolves in 88 days Virtually no atmosphere Many craters Surface Temperature: 427 °C facing Sun, -187 °C away from Sun

Venus Hottest planet: 460 °C Greenhouse effect: warming of the atmosphere because of heat trapped by Sun Rotates from east to west; 243 Earth days

Earth Mild surface temperature that changes little Dense protective atmosphere Only planet to have liquid water

Mars Reddish color; iron oxide Similar rotation with Earth; 24 hrs, 38 min. Longer revolution; 687 Earth days Thin atmosphere; colder Two moons Only frozen water exists

The Outer Planets Jupiter, Saturn, Uranus, Neptune Made of frozen gas and liquid, with a small solid core All have a ring system Large size and high mass Low density Many moons High gravity

Jupiter Largest planet Colorful bands of gases where storms take place Fast rotation; 10 hours Great Red Spot; spinning windstorm which has lasted 300 years

Saturn Second largest planet 1000 individual rings, most visible and largest Stormy bands of clouds along the surface Rotates quickly; 11 hours Revolves once every 29 years

Uranus Rotates on its side; once every 17 hours Revolves once every 84 years At least 11 rings and 22 moons

Neptune Greenish blue atmosphere because of methane gas Four rings Great Dark Spot – as big as the Earth Rotates once every 16 hours Revolves once every 164 years

Pluto No longer considered a planet; dwarf planet No rings and thin atmosphere One moon Crosses Neptune’s orbit part of the time Rotates once every 6 days Revolves once every 248 years.

Other Objects in Solar System Asteroids – rocky objects, smaller than a planet, that orbit a star Asteroid belt – region between Mars and Jupiter where most asteroids orbit Sun Meteor – brief streak of light seen when an asteroid enters the Earth’s atmosphere and burns up Meteorite – asteroid that hits the surface of a planet or moon after traveling through space Comet – ball of ice, rock, frozen gas, and dust that orbits the Sun

Asteroids

Meteors and Meteorites

Comets

Stars Stars shine because of a process called fusion Fusion – process by which particles combine to form a new particle The source of energy for the Sun is hydrogen fusion By combining hydrogen atoms, the Sun produces a constant supply of energy in the form of heat and light.

Stars Magnitude – brightness of a star; determined by distance from Earth and amount of energy Apparent magnitude – how bright a star looks Absolute magnitude – how bright a star actually is if all the stars were the same distance from the Earth The more negative the magnitude, the brighter the star. Color – blue is hottest, red is coldest

Distance to Stars Light-year – distance that light travels in one year –1 light-year = 9.5 trillion kilometers Astronomical Unit (AU) – the distance between the Earth and the Sun –1 AU = 149,598,000 kilometers Parallax – the apparent shift in a star’s position because the position of the Earth –Used to measure distances of starts

Distance to Stars

The Life of a Star A star’s life cycle begins in a nebula, a cloud of gas and dust in space. Balance between gravity and fusion. Gravity causes a collapse, fusion causes heat and expansion Main sequence star – star, like our Sun, that is fusing gases together giving off light and heat.

The Life of a Star As fusion uses up hydrogen, the star expands to about 100 times it’s original size – Red Giant. Gravity overtakes the mass of the star, and it collapses. Temperature begins to increase and the outer layer is blown off forming a nova; brilliant explosion of a Red Giant. Center of nova becomes a small, white, hot dense star – white dwarf

The Life of a Star Star more massive than the sun, as it uses up hydrogen, it becomes a supergiant Supergiant collapses and becomes a supernova, a brilliant explosion of a supergiant. After the gases have left, a neutron star may remain; very small, very dense star However, if gravity is large, a black hole may form; a region in space with tremendous gravity that light cannot escape.

Constellations Constellation – pattern of stars seen from the Earth

Galaxies Galaxy – group of billions of stars Our galaxy is the Milky Way galaxy –100,000 light years thick and 10,000 light years wide Three types based on shape: –Elliptical –Irregular –Spiral