If there is a full moon visible from Paris one evening, twelve hours later in Australia there will be a full moon visible.

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1 Astronomy: Semester Review Topics, Concepts and Ideas After a full moon, about how long is it until the next new moon? Two weeks If there is a full moon visible from Paris one evening, twelve hours later in Australia there will be a full moon visible. Full moon Directly above the Earth's equator lies the Celestial equator in the sky. All celestial objects rise in the East and set in the West because the Earth is rotating from west to east. When it is summer in North America is the Earth farthest to the Sun. The equinox is the time when the number of daylight hours equals the number of nighttime hours everywhere on the Earth. When the Moon and the Sun lie exactly in the same direction in the sky, what phase of the Moon would you see? New Full Moon sets at Sunrise. On March 21 and September 22 the Sun rises exactly due east and sets exactly due west. In the Northern Hemisphere, between what dates does the location of the Sun's rising and setting shift a little farther south each day? From June 21 until December 21 Because the Earth revolves around the Sun the constellations that are visible in the sky at night change with the seasons The ecliptic is the extension of the Earth's path on the celestial sphere. The ecliptic is tilted with respect to the celestial equator causes the seasons. The tilt of the Earth's spin axis relative to the Earth's orbit causes the seasons. During the equinoxes the Sun is on the ecliptic, the Sun is on the celestial equator, the Sun rises due east and sets due west The Third quarter phase of the Moon sets at noon. The full Moon phase occurs when the Earth is between the Sun and the Moon. The new Moon phase occurs when the Moon is between the Earth and the Sun. The first quarter phase of the Moon you would expect to see high in the sky at 6:00 pm. Waning crescent phase of the Moon you would expect to see rising at dawn. If the Moon sets at 10 a.m. today, approximately what time did the Moon set yesterday? 9:10 a.m.

2 During a full Moon phase you might expect to observe a lunar eclipse. During a new Moon phase you might expect to observe a solar eclipse. Solar eclipses can occur during new Moon. Relative to the stars, the Moon moves from West to East. For someone in the northern hemisphere stars rise in the east and set in the west For someone in the southern hemisphere the situation is the same stars also rise in the east and set in the west. The motion of the Sun relative to the stars is from West to East. During a solar eclipse, the Moon casts a small circular shadow on the Earth. Lunar eclipses do not occur every full Moon, because the path of the Earth is tilted relative to the ecliptic. A lunar eclipse is visible from any location on the night-side of the Earth. An annular eclipse occurs when the Moon's shadow does not completely reach the Earth during a solar eclipse. At totality during the lunar eclipse, the Moon generally appears reddish in color. 7 (five solar and two lunar) or 7 (four solar and three lunar) is the maximum number of eclipses that can occur in a year. Eclipses generally occur in pairs, with a solar eclipse about two weeks before or after a lunar eclipse. An annular solar eclipse occurs when the Moon in its orbit is farthest from the Earth, and, so not able to cover the complete disk of the Sun. The stars move parallel to the celestial equator. Are the Sun and the Moon ever above the horizon at the same time? Yes, sometimes. The moon appears larger when it rises than when it is high in the sky because it's an illusion from comparison to objects on the horizon. Kepler's third, or harmonic, law states that the Semi-major axis of an orbit cubed equals the period squared. The paths of the planets on the sky are tilted with respect to the celestial equator by about 23 degrees. Copernicus' heliocentric model failed to work as well as it might to predict the positions of planets because Copernicus insisted the orbits were circular.

3 One of Tycho Brahe's major contributions to astronomy was to prove that a supernova (exploding star); much farther away than the planets was and a comet; outside the Earth's atmosphere. Eratsothenes was the first person to measure the circumference of the Earth. One of the methods used to date supernova remnants (the remains of exploded stars) today is by using the records of ancient Chinese, Japanese, and Korean astronomers. The Sun, Planets, Earth and Moon pass through the zodiac. Occasional east to west motion of the planets relative to the stars over many successive nights is retrograde motion. In Heliocentric models, the Sun is assumed as the center of the solar system. During retrograde motion, a planet moves from East to West relative to the stars. Retrograde motion is discernible by watching a planet over the course of many nights. Galileo was the first to observe the phases of Venus. In Copernicus' model of the solar system, the planets orbited the Sun in circular orbits. Tycho Brahe's major contribution to astronomy is his extensive series of measurements of planetary positions. Kepler used the extensive records of planetary positions measured by Tycho to discover that the orbits of the planets are elliptical. Kepler's first law states that the orbits of planets are elliptical, with the Sun at one focus. From Kepler's second law, we conclude that the planets do not move with constant speed. From Kepler's third law, we conclude that Mars completes a full orbit much faster than Pluto. Observations indicate that it takes Saturn longer than Jupiter to complete one orbit about the Sun. This is in agreement with Kepler s third law. The time between the vernal equinox and the autumnal equinox is somewhat greater than the time between the autumnal equinox and the vernal equinox. This is a result of Kepler's second law. Imagine the much more massive Jupiter were to switch places with the less massive Mercury. Which of the following would accurately describe the outcome? Jupiter would orbit the Sun in less time than it did before. The pattern of Little Dipper in the sky is an example of an asterism. An easily recognizable group of stars that seems to make a pattern or figure is called an asterism.

4 It is important to increase your camera's exposure time when taking astronomy pictures because cameras receive very little light from the astronomical sources and so a longer exposure time allows for more light to be collected. Polaris is a star that almost stays stationary in the sky throughout the night. A star which is located on the celestial equator would have a 0 declination. If you are standing on the Earth's South Pole, the South celestial pole would be on your zenith. Right Ascension and declination for a star remains the same throughout the night. In Opposition configuration Mars would appear the brightest. In the Conjunction configuration an outer planet will be farthest from the Earth. Venus never appears opposite to the Sun in the sky because Venus can go maximum only 47 away from the Sun with respect to us. Star-trail photography is photography resulting from the Earth's rotation smearing the star image in to a streak. Your eyes respond best in the dark to the color of blue. Declination is measured in degrees, north or south of the celestial equator. Right ascension is measured in hours along the celestial equator, starting from the vernal equinox. Declination is analogous to latitude in geographic coordinates. Right ascension is analogous to longitude in geographic coordinates. The time between two successive superior conjunctions of Mars is equal to the synodic period of Mars. Mercury appears brightest at the location of greatest elongation It takes the human eye about twenty minutes to adapt to the darkness of the night sky. Inertia is the property that summarizes a body's tendency to stay in the state of rest or motion. Newton's first law of motion states that a body at rest stays at rest unless a force is applied to it and a body in motion stays in motion unless a force is applied to it.

5 The recoil experienced when firing a shotgun is a consequence of Newton's 3 rd law. In your office, you have a rolling chair and a rolling filing cabinet. The chair weighs 10 pounds, and the filing cabinet weighs 50 pounds (it's partly full). If you push both of them away with about the same strength the chair will accelerate about 5 times as much as the cabinet. The force that pulls an upward going ball back to the Earth and keeps the Moon in its orbit is called gravity. If you double the distance between two bodies, the force of gravity between them would decrease by a fourth. The Moon is gravitationally attracted to the Earth. Is the Earth gravitationally attracted to the Moon? Yes and the force of attraction is the same. When an astronaut experiences weightlessness in space, their mass is the same as on the Earth. At the equator, you weigh less than anywhere on the Earth. The Earth's radius at the equator is larger than that at the poles. At the North and South Poles the Earth's surface gravity more. Escape velocity is the speed an object needs to move away from the gravitational pull of the Earth. If a newly discovered planet has four times the mass of the Earth but it still has the same surface gravity as Earth, how big must this new planet be? Twice as large as Earth While riding a bicycle, if you stop pedaling you will still continue to move forward due to Inertia. After tying a string to a rock, you twirl the rock around above your head. If the string were to break, what path would the rock follow a straight line before falling down. Consider a large truck and a small car driving up a straight steep hill. The truck is moving at 60 miles per hour and the car at 30 miles per hour. Assuming that the speeds are constant, which of the two vehicles experiences a larger net force? The same: zero net force. Suppose that the Sun started shrinking in size, without losing any mass. What would be the effect of the Sun's change on the orbits of the planets? The orbits would not be affected. Newton's modification of Kepler's 3 rd law allows astronomers to determine the mass of celestial objects.

6 If the net force acting on an object doubles, then the acceleration doubles as well. When a bus makes a sudden stop the passengers lurch forward as a consequence of Newton's 1 st law. In materials like glass or water the speed of light is reduced. Radio waves range in wavelength from millimeters to hundreds of meters. Even though X-rays have higher energy, they move with the same speed as that of visible light. Star A is blue, Star B is yellow, and Star C is red. Which one of these is the hottest star? Star A Adam's toy gun emits blue light, Sue's emits red light, Bonnie's emits infrared light, and James' emits ultraviolet light. Which gun produces the most energetic light? James The Sun emits a spectrum very close to a blackbody spectrum. A stove burner is an example of a blackbody that you see in everyday life. The electrons are quantized in an atom. That means the electrons can stay only in specific orbits. Excitation occurs when an electron in an atom jumps from a lower energy orbital to a higher energy orbital. You are heating a jar full of hydrogen and observing its spectrum. When you add more hydrogen to it, what happens to the spectral lines in the spectrum? The positions of emission lines will remain the same but the lines will get broader and brighter. A(n) absorption spectrum has dark lines on a continuous background. A(n) emission spectrum has bright lines on dark background. An object is moving very fast perpendicularly to your line of sight. What shift will you observe in its spectrum? No shift X-rays are completely blocked by the Earth's atmosphere. An atmospheric window is a range of wavelengths of electromagnetic radiation which transmit through the Earth's atmosphere. Wien's law allows astronomers to measure the surface temperature of the star. The number of protons in the nucleus determines the identity of a chemical element.

7 When an electron in an atom absorbs a photon the electron moves to a higher energy level. When astronomers study the light emitted from the Sun they notice that the light emitted from the east limb (edge) is blueshifted while the light emitted west limb is redshifted. The reason for this is that the Sun is rotating. As a solid is heated (from a low to a high temperature) the radiated light will move through what sequence of colors? Red, yellow, blue Spectral lines shifted toward higher frequencies are called Blue-shifted. A photon is a particle of light. The spectral lines of a star will appear Red-shifted (i.e., shifted toward the longer wavelengths) if the star is moving away from the Earth. Electrical attraction holds the electron in orbit around the nucleus of the hydrogen atom. A photon of blue light has more energy than a photon of red light. If a photon's frequency increases its wavelength Will decrease. A night vision camera uses a detector sensitive to infrared light, so you can see objects that are warmer than their surroundings. Conservation of energy requires that if an atom absorbs a photon an electron rises to a new orbital with an energy equal to that of the previous orbital plus the energy of the photon. Using Interferometry, scientists can use a few smaller telescopes to take images with the same resolution as a much larger telescope. To double the resolving power of a telescope, you must Increase the diameter by a factor of two. A warm dust cloud in which stars are forming would be best observed with a(n) Infrared. A galaxy with almost no starlight but plenty of cool clouds of hydrogen gas would be best observed with a(n) Radio telescope. In a false color image, colors can represent photon energies or the intensity of electromagnetic radiation. Ignoring the effects of the atmosphere, what is the theoretical resolution of an 8 inch telescope (about 20 cm) if you are looking at visible light with a wavelength of about 500 nm? About half an arcsecond.

8 If your pupils have a diameter of about 5mm, about how many times more light gathering power does a telescope with a diameter of about 20 cm (8 inches) have than your pupils? 1600 times The resolving power of a telescope is affected by the property of light called Diffraction. One of the biggest problems for ground based astronomy today is Light pollution makes it difficult to observe faint objects. The two most important properties of any telescope are the light gathering power and the resolving power. A pencil inside a water glass appears to be bent because of refraction of light. The larger refraction near the horizon lifts the lower edge of the Sun more than the upper edge and makes the Sun look flattened. The Moon appears bigger near the horizon due to an optical illusion. Disadvantages of using a single, large lens in a telescope Large lenses are expensive to fabricate are: A lens has to be supported only at its edges, so the lens can sag in the middle. Different colors of white light on passing through a lens focus at different points and result in a blurred image. Some lens materials completely absorb short wavelengths. The ability of a telescope to show two very close objects separately is called its resolving power. "seeing is the distortion of an image due to an atmospheric turbulence. The best site for placing an X-ray telescope is above the Earth's atmosphere. The best site for placing a ground-based optical telescope is a mountain top.x-rays are blocked by ozone and oxygen present in the Earth's atmosphere. Stars twinkle due to the refraction caused by atmospheric irregularities. Charge-coupled device (CCD) is the most efficient means of recording light. The Chandra Observatory is a space telescope that observes X-rays. An inherent disadvantage of radio telescopes is they are very weak, and their photons do not penetrate the atmosphere easily. Radio telescopes are most suitable for observing cool gas clouds.

9 Resolving power is the most important quality of an astronomical telescope. If a 3 meter diameter telescope is doubled in size, then its new light collecting power would increase by a factor of four. The effect of tripling the size of a telescope's primary mirror is to triple its resolving power. An optical telescope is able to resolve blue objects better than red objects.