ASTR 205 Exam Study Guide

Scientific notation is used in science because - it makes it easy to write big or small numbers. The average distance from Earth to the sun is - 1 AU The sun is - a star 1 AU from Earth. more than 100 times the diameter of Earth. A galaxy contains - gas, dust, and stars, and a lot of dark matter. The Milky Way Galaxy - contains about 100 billion stars. 2.9×107 is the same as - . 29 million It takes light 1.3 seconds to travel from the moon to Earth and 8 minutes to travel from the sun to - The sun is 370 times further from Earth than the moon. If light takes 8 minutes to travel from the sun to Earth and 5 hours to travel from the sun to Pluto, whatis the distance from the sun to Pluto? - 37.5 AU The speed of light is 3.0×105 km/sec, and it takes light 1.3 sec for light to travel from the moon to Earth. From this information, what is the distance to the moon? - 390,000 km If the distance to the nearest star is 4.2 light-years, then a. the star is 4.2 million AU away. - the light we see left the star 4.2 years ago. The Milky Way Galaxy is - a spiral galaxy. part of a cluster of galaxies that contains a few dozen galaxies. about 75,000 light years in diameter. Which sequence is correct when ordered by increasing size? - Earth, Solar System, Milky Way, galaxy clusters How is a planet different than a star? - Planets reflect light while stars produce their own light If the distance from the Sun to the Earth is represent by roughly 15 meters, then the distance from the Earth to the Moon on the same scale would be - small than your hand. How is a planet different than a star? - Planets reflect light while stars produce their own light. Constellation names are in - latin Seen from the northern latitudes, the star Polaris - . is always above the northern horizon. The celestial equator is - a line around the sky directly above Earth's equator. the dividing line between the north and south celestial hemispheres. The ________ is the point on the celestial sphere directly above any observer. - zenith Most star names, such as Aldebaran and Betelgeuse are - arabic The magnitude scale - can be used to indicate the apparent intensity of a celestial object. The apparent visual magnitude of a star is a measure of the star's a. size. - intensity. The star Vega has an apparent visual magnitude of 0.03 and the star HR 4374 has an apparent visual magnitude of 4.87. It has been determined that both stars are at the same distance from Earth. What does this information tell us about the two stars? - Vega must produce more energy than HR 4374. The _______________ of an object depends on the diameter of the object and the distance to the object. - apparent diameter An observer's nadir is - the point directly opposite the observer's zenith. A(n) __________________ is one-3,600th of a degree. a. precession - second of arc The Big Dipper is - an asterism. . Precession of the rotation axis of Earth is caused by - the force of gravity from the sun and moon on Earth's equatorial bulge. An observer in the Northern Hemisphere watches the sky for several hours. Due to the motion of Earth, this observer notices that the stars near the north celestial pole appear to move - . counter clockwise around the celestial pole. You live at a latitude of 73° N. What is the angle between the northern horizon and the north celestial pole? - 73° . You live at a latitude of 39° S. What is the angle between the southern horizon and the south celestial pole? - 39° If the north celestial pole appears on your horizon, what is your latitude? - 0° Which star in the table to the right would appear the brightest to an observer on Earth? - α CMa Based on the information in the table to the right, what is the ratio of the intensity of δ Dra to that of Nim? - 100 Which star in the table to the right would not be visible to the unaided eye of an observer on Earth - Nim Star A has an apparent visual magnitude of 13.4 and star B has an apparent visual magnitude of 15.4. Star A is _________________ than star B. - 6.3 times brighter Polaris is a second magnitude star, and Phi Pegasi is about 16 times fainter than Polaris. What is the approximate magnitude of Phi Pegasi? - 5 Which of the following statements correctly describes the relationship between stars and constellations? - Every star is located in a constellation. How much of the night sky is north of the celestial equator? - Exactly one-half. If the Sun passes directly overhead on at least one day per year, then - you are within 23.° latitude of the equator. . If you are standing at the Earth's North Pole, which of the following would be located at the zenith? - The north celestial pole For stars the same constellation they - may actually be very far away from each other. . During the month of June the north celestial pole points towards Polaris but during the month of December it points - still towards Polaris. If the Earth's period of rotation doubled, but the period of revolution stayed the same - the night would be half as long. The ecliptic is - the centerline of the zodiac. the projection of Earth's orbit on the sky. the apparent path of the sun around the sky. At what two celestial locations do the celestial equator and ecliptic coincide? a. winter solstice and summer solstice - vernal equinox and autumnal equinox On the vernal equinox the sun is - on the celestial equator and moving north with respect to the equator. A solar or lunar eclipse will occur - when the sun is near the line of nodes of the moon and the moon is new or full. The sideral period of the moon - is about 27.32 days long. is the period of time for the moon to orbit Earth once with respect to the stars. .The moon has an angular diameter of 0.5°. What is the moon's angular diameter in minutes of arc? - 30 If the plane of the Earth's equator were not tilted with respect to the ecliptic plane a. the daylight period of Earth would be the same year-round. - the daylight period of Earth would be the same year-round. there would be no seasonal changes. Earth's poles would not experience six month long nights. The phase of the Moon on a particular night is determined by a. the season of the year. - the relative positions of the Sun, Earth, and Moon. On a clear night when an observer in Los Angeles sees a first quarter Moon an observer in London would see - a first quarter moon. The Moon's angular diameter in our sky is measured to be 0.5°. From this, we can find - diameter of the Moon if we know the Moon's distance. The lowest amount of solar energy per square meter is incident upon the surface of Earth in the northern hemisphere on or about - December 21, the winter solstice. Which of the following people did not accept a heliocentric model for the universe? - Tycho Parallax is - the apparent motion of an object due to the motion of the observer. The Copernican system was no more accurate than the Ptolemaic system in predicting the positions of - the Copernican system included uniform circular motion. Galileo's telescopic discoveries of mountains on the moon and spots on the sun were controversial - were not perfect spheres. Tycho's universe was the same as the Copernican universe except that - Earth did not move. Tycho Brahe's greatest contribution to astronomy was - his 20 years of careful observations of the planets. When we say that gravitation is universal we mean that - it is a property of all matter. Newton concluded that some force had to act on the moon because - a force is needed to pull the moon away from straight-line motion. Kepler's second law implies that - a planet should move at its greatest speed when it is closest to the sun. Kepler's first law of planetary motion implies that - the distance between the planet and the sun changes as the planet orbits the sun. Gravity obeys an inverse square relation. This statement implies that the force due to gravity between two masses - will decrease as the square of the distance between the two masses increases. An object has been located orbiting the sun at a distance from the sun of 65 AU, what is the approximate orbital period of this object? - 524 years Saturn is on average 10 AU from the sun. What is the approximate orbital period of Saturn? - 32 years . In pre-Copernican astronomy, it was almost universally believed that - . the Earth was at the center of the universe. . When Mars is located directly behind the Earth with respect to the Sun in its orbit, it is - at the midpoint in the sky between east and west at midnight. The greatest inaccuracy in Copernicus' model of the solar system was that the planets - travel in circular orbits with uniform motion. Which of the following statements best describes Kelper's 3rd law of planetary motion? - The larger the orbit, the longer its orbital period. ____________ has (have) wavelengths that are longer than visible light. - Infrared radiation . The energy of a photon - is inversely proportional to the wavelength of the light. Long wavelength visible light - will appear red in color to the average human eye. Photons of blue light - have a greater energy than photons of red light. A nanometer is - a unit of length. What is the relationship between color and wavelength for light? - Wavelength increases from blue light to red light