Astronomy Review Guide

Review Guide for Astronomy Summative

Concept 3: Earth in the Solar System

PO1: Explain the phases of the Moon in terms of the relative positions of the Earth, Sun, and Moon.

Earth’s Moon  Our moon is the closest celestial object to Earth.  A moon is a naturally occurring satellite or an object that orbits another object.  It takes one month for our moon to orbit the Earth.  Our moon orbits the Earth twelve times for every time that the Earth orbits the Sun (a year).  When the moon lies between the Sun and the Earth so the entire side of the moon is dark and the moon is not visible it is called the new moon.  When the moon is aligned with the Sun and Earth, with the Earth being in the middle, and then entire side of the moon facing Earth is bright and visible it is called a full moon.  When we see the right hand half of the moon lit up it is called 1st quarter.  When we see the left hand half of the moon lit up it is called 3rd quarter.  A gibbous moon is when we see more than one quarter of the moon.  A crescent moon is when we see less than one quarter of the moon.  Between a new moon and a full moon we see more and more of the moon and it is called a waxing moon.  Between a full moon and a new moon we see less and less of the moon and it is called a waning moon.  After a new moon, we begin to see the right hand portion of the moon first.  The moon does not produce its own light but instead reflects the sun’s light.  To identify the phases remember that it goes from right to left, light to dark  (1) New Moon (2) Waxing Crescent (3) 1st Quarter (4) Waxing Gibbous (5) Full Moon (6) Waning Gibbous (7) 3rd Quarter (8) Waning Crescent

PO2: Construct a model for the relative positions of the Earth, Sun, and Moon as they relate to corresponding eclipses.

Eclipses  Eclipses occur when one object blocks sunlight from another.  The two types of eclipses are solar (Sun is blocked from Earth’s view) and lunar (moon is not visible from Earth).  Solar eclipses occur when the moon passes between the Sun and the Earth blocking the Sun from view on Earth.  Lunar eclipses occur when the Earth passes between the moon and Sun blocking the sunlight from reaching the moon.  When the Sun’s disk is covered in a total solar eclipse the corona of the Sun is visible.  A full or total eclipse is when the entire Sun or moon is blocked from view and a partial eclipse is when only a portion of the Sun or moon is blocked from view.  Total solar eclipses are the rarest type of eclipse.

PO3: Explain the interrelationship between the Earth’s tides and the Moon.

Tides  The tides on Earth are created by the moon’s gravitational pull on Earth.  Any single location on Earth will experience two high tides and two low tides per day.  High tide is experienced when the moon is directly overhead or exactly on the opposite side of the Earth.  Spring tides occur when the sun and moon line up and their gravitational pulls combine to create larger tidal differences.  Neap tides occur when the sun and moon are at 90 degree angles to each other and their gravitational forces counteract each other and create smaller tidal changes.

PO4: Explain the seasons in the Northern and Southern Hemispheres in terms of the tilt of the Earth’s axis relative to the Earth’s revolution around the Sun.

Seasons  The reason for seasons is that the Earth is tilted at 23 ½ degrees and so the length of daylight changes along with the angle at which the Sun’s rays strike the Earth.  When your hemisphere (northern or southern) is titled toward the Sun you are experiencing summer.  When your hemisphere (northern or southern) is tilted away from the Sun you are experiencing winter.  When the hours of daylight and night times are equal in both hemispheres (northern and southern) it is called and equinox and it occurs in the fall and spring of the year. (September 21 and March 21)  The longest day of the year is called the summer solstice. (June 21)  The shortest day of the year is called the winter solstice. (December 21)  The Sun appears higher in the sky during the summer and stays up longer.  The Sun appears lower in the sky and is not up as long in the winter.  It is hotter in the summer and colder in the winter because the angle that the Sun’s rays hit the Earth changes throughout our orbit of the Sun since we are tilted at twenty three and a half degrees on our axis.  When it is summer here in North America, it would also be summer in China since it is also in the Northern hemisphere. (seasons are opposite by hemisphere) PO5: Identify the following major constellations visible (seasonally) from the Northern Hemisphere: (1) Orion (2) Ursa Major (Great Bear) (3) Cygnus (4) Scorpius (5) Cassiopeia

Constellations  A constellation is a group of stars that form a pattern or imaginary picture.  We see different constellations throughout the year because we are orbiting the Sun and are located at different positions in our solar system throughout the year.  Constellations that are located near the poles and that can be seen throughout the year are called circumpolar constellations.  There are eighty-eight identified or named constellations according to the International Astronomical Union.

PO6: Explain the relationship among common objects in the solar system, galaxy, and the universe.

The Planets  The inner planets are relatively closer together than the outer planets.  The outer planets are relatively farther apart than the inner planets.  The inner planets are rocky or terrestrial.  The outer planets are gas giants, except Pluto.  The outer planets have rings, except Pluto.  The outer planets have many more moons than the inner planets.  Saturn is most well known for its rings but is also the second largest planet in our solar system.  Jupiter is the largest planet in our solar system.  Pluto is the smallest planet in our solar system.  If you did not count Pluto as a planet, Mercury would be the smallest planet in our solar system.  The order of the planets, starting from the Sun, are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto (My Very Educated Mother Just Served Us Nine Pizzas).  The planets orbit the Sun in elliptical orbits.  The inner planets (between the Sun and the asteroid belt) include Mercury, Venus, Earth, and Mars.  The outer planets (beyond the asteroid belt) include Jupiter, Saturn, Uranus, Neptune, and Pluto.  An astronomical unit or AU is the distance that the Earth is from the Sun and is equal to about 93 million miles.  Because Mercury has long days (rotates slowly in its axis) and short years (orbits the sun quickly) the Sun appears to move backward at times.  Venus is the brightest object in the sky besides the Sun and our Moon.  Venus is known as Earth’s sister planet because it is just about the same diameter and mass as Earth.  Venus is the hottest planet because its atmosphere is 97% carbon dioxide creating a severe greenhouse effect.  Venus is considered probably the least fit planet for living things.  Venus is the most volcanic planet in our solar system.  Mars is known as the Red Planet because of its reddish iron-rich soil.  Mars is probably the most similar to Earth of all the planets because it has seasons, polar ice caps, volcanoes, and wind storms.  Mars contains the largest volcano in our solar system (Olympus Monds) along with a huge canyon named Valles Marineres.  Even though Saturn is the second largest planet in our solar system, its density is so low it could float if it were thrown into a huge lake.  Uranus is tipped ninety degrees over onto its side so that its rings appear to circle it from top to bottom.  Because Uranus is tilted ninety degrees on its side, it experiences strange seasons with one pole in sunlight for forty two years and the other in darkness for forty two years.  Neptune is bluish in color due to the methane gases.  Pluto was declassified as a planet in 2006 by the International Astronomical Union and is now considered a “dwarf planet.”  Unlike the other outer planets that are gas giants, Pluto is made of frozen ice and rock.  Pluto is the only planet whose orbit crosses another planet’s orbit (Neptune).

Meteoroids, Meteors, Meteorites  Meteoroids are pieces of rock moving in space.  A meteor is a meteoroid that has entered our atmosphere and is burning due to the friction with the atmosphere.  Another name for a meteor is a shooting or falling star.  A meteorite is a piece of material from space that lands on Earth.  A meteorite is a meteor that has not completely burned up in Earth’s atmosphere and therefore impacts the Earth.  One of the most famous meteorite craters in the United States is located near Flagstaff, Arizona.

Comets  Comets are also called dirty snowballs because they are frozen chunks of ice and dust that orbit the Sun.  A comet’s tail can extend for millions of miles.  Comets come from the Oort Cloud and Kuiper Belt which are beyond Pluto in our solar system.  One of the most famous comets is Halley’s Comet which can be seen every seventy-six years.  As comets near the Sun they melt and the solar wind pushes the particles away from it creating a tail.  A comet’s tail always points away from the Sun.  A comet’s tail lengthens as it nears the Sun and shortens as it moves away from the Sun.  Comets orbit the Sun in an elliptical orbit meaning that they get close to the Sun and then very far from the Sun.  A comet does not radiate light of its own but instead reflects the Sun’s light so we can see it.

Asteroids  Most asteroids are found in a region between Mars and Jupiter called the asteroid belt.  Scientists believe that asteroids may be pieces of a planet that was torn apart millions of years ago.  An asteroid crashing into the Earth is thought to be the reason that the dinosaurs became extinct.  Asteroids are fragments of rock and metal that orbit the Sun.  Asteroids are generally irregular in shape rather than spheres.  Asteroids are usually reddish or black in color.  Asteroids are often called minor planets.  The area near Jupiter where no asteroids are found is called the Kirkwood Gap.  Asteroids are thought to be what caused the craters on many of the planets and the moons.  An asteroid is a fragment of matter similar in composition to planets that orbits the Sun.  When asteroids collide and break apart they might become meteoroids.

Miscellaneous Astronomy  The Big Bang Theory explains the formation of the universe by stating that everything at one time was in a single sphere that exploded and as gravity took effect on that matter it clumped together in some regions creating our planets, moons, etc.  If it is noon where you are, it is midnight on the exact opposite side of the Earth.  The Earth rotates on its own axis and it takes twenty-four hours to rotate once equaling a day.  The Earth’s rotational period is twenty-four hours.  The Earth orbits the Sun and it takes three hundred and sixty five days to complete one orbit equaling a year.  The Earth’s orbital period is how long it takes to orbit the Sun once.  The Earth’s orbit around the Sun is almost a perfect circle so the distance between the Earth and the Sun does not change throughout the year.  The Earth’s northern pole points almost directly at the North Star or Polaris.  We move just under one degree per day in our orbit around the Sun.  Our galaxy, the Milky Way, is a spiral galaxy that from the side looks like a flat disk with a bulge in the middle and from the top it looks like an “octopus in a washing machine.”  Astronomy is the scientific study of space including the planets, stars, galaxies, comets, and nebulae.

PO7: Describe the sun's structure and energy. (i.e., layers of sun, production of energy in stars, visible and invisible parts of electromagnetic spectrum.

The Sun  The sun appears to rise in the east and set in the west because the Earth is rotating on its own axis.  Sunspots are cool areas and appear as dark patches on the Sun.  Sunspots are caused by magnetic fields within the Sun slowing down the radiation of heat in some areas.  Sunspots are a form of solar storm.  The Earth’s magnetic field protects us from most harmful solar radiation.  The northern and southern lights appear where Earth’s magnetic field interacts with the solar wind or sun’s magnetic radiation.  The Sun is the most massive object in our solar system making up 99.86% of the solar system’s mass.  One million Earth’s could fit within the Sun.  The outer layer of the Sun’s atmosphere that is visible during a total solar eclipse is called the corona.  The solar wind is a continuous stream of high-energy particles released into space in all directions from the Sun.  The Sun is the center of our solar system because it is the largest object and therefore has the greatest gravitational pull capturing us and the other planets and causing our orbits of it.  The Sun produces energy through nuclear fusion which is the conversion of hydrogen atoms into helium atoms.  The Earth is one astronomical unit (AU) form the Sun which is about 93 million miles.  Solar storms on the sun include sunspots (dark patches), flares (explosions that burst from sunspots) and prominences (bright arches of gases)

Stars  The distance that light travels in one year is called a light-year.  Polaris is another name for the North Star.  A galaxy is a huge collection of stars, planets, and other celestial bodies.  The Sun is the only star in our solar system.  The billions of stars are located way beyond the planets in our solar system.  Stars are present in the sky during the day but cannot be seen because the Sun is brighter, and closer, than the stars.  Stars are born out of nebulae or clouds of dust and gas.  A star is a glowing ball of gas.  A supernova is an exploding star.  Neutron star  Pulsar  White dwarf  Black hole  Color and temperature  The life cycle of a star is dependent upon the mass of a star.