Astronomy 101 Exam 2025

Astronomy 101 Exam 2025 What is astronomy? - -the study of object's and phenomena beyond Earth's atmosphere [goal: to understand the physics of the Universe] What is astrology? - -the belief that the position of heavenly bodies, and celestial events correlate with Earthly events and Human events How do you determine your astrological sign? - -the position of the Sun in a particular zodiacal constellation on the day you were born [in ancient Greece] due to procession the signs from ancient Greece are about 1 sign off. ei If Sun is in Pisces the day you were born, you were Aquarius in ancient Greece What is special about the constellations that make up the zodiac? - -these constellations are defined by the path of the Sun throughout the year [Moon&planets also move through these constellations] If the Sun is in Taurus at noon, what constellation will it be in at sunset? - -Taurus [21 days to touch Gemini's toes]]; 5.8%/365 day orbit. Our perception of the Sun's occupation of a particular zodiac sign will shift as the Earth progresses in its 365 day orbit around the Sun How many constellations does the sun move through in a year? - -technically the 13 along the celestial equator What is special about Polaris? - -this is our modern North Star as it sits very near to Earth's projected North Pole, [in ~2850 BP N*= Thuban] constellation - -an area of sky containing an accidental pattern of stars named after a person, animal, or object; helps people locate objects in the sky asterism - -a pattern of stars not recognized by the International Astronomical Union as a constellation [ie Big Dipper] IAU - -International Astronomical Union established 88 constellations with precise boundaries so that every portion of the sky is contained within a constellation Are stars within constellations bound by gravity? - -No, the pattern will change with time as stars move In Winter the Sun - -rise:South of East --- set:South of West In Summer the Sun - -rise: North of East --- set North of West Astronomy On the Equinoxes the Sun - -rise: East --- set: West Seasons are caused by - -the tilt of the Earth on it's axis Summer season - -Sun is in the sky longer, more times to heat up the Earth, When the Sun is higher - -sunlight hits the surface of more directly and shines more energy over a smaller area When the Sun is lower - -sunlight hits the surface at an angle and shines over a a wider area [with less concentration] South Pole= - -South Celestial Pole North Pole= - -North Celestial Pole Equater= - -Celestial Equator Latitude [0°@equator]= - -Declination [0°@celestial equator] Longitude [0hrs@meridian]]= - -Right Acsension [0hrs@vernal equinox] Altitude of the North star= - -your latitude on Earth Declination of circumpolar stars= - -90°- latitude [these stars will never set below this horizon] Altitude of the celestial equator= - -90°- latitude During the vernal/atumnal equinoxes the Sun - -sits on the celestial equator, the celestial equator and the ecliptic intersect Summer solstice: Sun is 23.5° - -above the celestial equator Winter Solstice: Sun is 23.5° - -below the celestial equator The moon rotates on it's axis at the same rate - -it is orbiting around the Earth Sidereal Month [one orbit around the Earth] - -27.3 days Synodic Month [one lunar phase cycle] - -29.5 days Lunar eclipse - -the moon enters the Earths shadow Solar eclipse - -portion of the Earth enters the Moon's shadow Astronomy Astronomy Astronomy Total Solar Eclipse - -occurs when Earth passes through the umbra of the Moon's shadow so that the disk of the Sun is completely blocked by the Moon. Waxing Moon - -New moon --- shadow on the left Waning Moon - -Full moon --- shadow on the right Blue Moon - -2nd full moon within a month Lunar year - -twelve lunar months that amount to 354 days Gregorian year - -365.2425 days 1 day off every 3,300 yrs; no LeapYear on years not divisible by 400 Total Lunar Eclipse - -moon enters the Earth's shadow[umbra] completely, occurs only during a Full moon retrograde motion - -+as Earth over-takes outter planets in their orbits they will appear to move backwards +as inner planets overtake Earth in their orbit they appear to move backwards Ptolemy's retrograde motion - -13th century, added 40-60 epicycles to each planet to make it appear brighter/dimmer; model persists for 1400yrs but can only get a planet so close to Earth Epicycle Solution Model --good: - -explained retrograde motion and the planets' varying brightness Epicycle Solution Model --bad: - -not accurate enough to explain the motion of planets & cannot account for brightness variation over periods of time Copernicus' retrograde motion - -couldn't predict planetary motion because he assumed that planets had circular orbits at a constant speed, to improve his predictions [planetary positions] he (+)an epicycle Kepler's retrograde motion - -explain this motion using ellipticals Copernicus' explaination motion of *'s, planets, Sun - -this Polish cleric's heliocentric model was later published by Bishop of Kulm: the Earth spins once on its axis and like the other planets orbits the sun, Only the Moon orbits the Earth --observes daily/seasonal changes&retrograde motion Why did the ancient Greeks think the Earth was at the center of the universe? - -Sun, Moon and stars seemed to orbit the Earth, and Earth's rotation and revolution[orbit] are not felt, and they did not see parallax Astronomy Astronomy Demonstrate that the Earth is NOT at the center of the Universe - -with use of a telescope exhibit/portray stellar parallax and phases of Venus parallax - -apparent motions of a relatively close object with respect to a more distant object as the location of the observer changes Venus' phases - -........................................1/4 Earth-------New------------SUN-----------------Full .......................................1/4 AU - -distance from the Earth to the Sun ~ 93 million miles Ly - -distance light travels in a year ~ 6 trillion miles Galileo's discoveries - -heavens are not perfect/immutable, moons orbit Jupiter, Venus has a full set of phases Kepler's 1st Law of Planetary Motion - -orbits of planets are ellipses, with the Sun at one focal point of the ellipse Kepler's 2nd Law of Planetary Motion - -the line joining the planet to the Sun sweeps out equal areas in equal times as the planet travels around the ellipse BUT planets move faster when closer to the Sun and slower when farther from the Sun Kepler's 3rd Law of Planetary Motion - -the ratio of the square of the revolutionary periods for two planets is equal to the ratio of the cube of their semi-major axis Kepler's 3rd Law FORMULA - -R³=P² Copernicus - -planets move in epicycles as they orbit the Sun Kepler - -planets orbit around the Sun in ellipses Aristotle - -planets move around the Earth in crystalline spheres Ptolemy - -planets move in epicycles as they go around the Earth Tycho - -planets orbit the Sun as the Sun orbits around the Earth What planets are always found close to the Sun? - -Mercury within 28°, Venus within 46° significance of Venus' phases - -this dicovery[Galileo] lends evidence to heliocentricity Newton's 1st Law of Motion - -unless an object is acted upon by a net outside force, the object will maintain a constant speed in a straight line, or remain at rest Astronomy Astronomy Newton's 2nd Law of Motion - -a net external force applied to an object cause it to accelerate at a rate that is proportional to the force and inversely proportional to its mass Newton's 3rd Law of Motion - -for every action there is an equal and opposite reaction Newton's 2nd Law FORMULA - -F=M(A) What does Newton's 2nd Law really mean? - -double the force= double the acceleration, inversely double mass acceleration= 1/2 mass mass - -an intrinsic property of the object and remains the same independent of where it is in the Universe weight - -downward force experienced by an object as a result of the gravitational interaction of the Earth or other body Newtons Law of Universal Gravitation - -every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them Newtons Law of Universal Gravitation FORMULA - -F=Gm1m2/d² Einsteins Theory of Gravity - -light bends around mass if m1 increases by a factor of 4, [F=Gm1m2/d²] then - -force=4x if distance increases by a factor of 4 F=Gm1m2/d²] then - -force=1/16 Newton's Law's applied to gravity - -the bigger the mass the more it attracts, if mass increases force of gravity increases Newton vs. Einstein - -theories works with areas of weak gravity[eg Earth] VS. theories works with areas of high gravity [egSun] observations unexplained by Newton's Laws - -bending of starlight, the full precession of Mercury's orbit Einstein Theory of Relativity - -explained gravity as a result of the curvature of space time near the presence of a mass, also based on the principle of equivalence Principle of Equivalence - --the gravitational force acting between two objects is proportional to their masses, -the inertial mass equals the gravitational mass, -Inertial forces[felt while accelerating] are indistinguishable from gravitational forces Astronomy If Charlene wanted to lose 3/4 of her weight what should she do? - -W=Wnormal/d² weight is inversely proportional to the square of the distance if Marvin weighs 36lbs on the surfance of the Earth what would her weigh at 2R[dist]? - if W= Wnormal/ d² and Wnormal=36, 36/2² = 36/4, W=9lbs at