Slide 1

The Night Sky Slide 2 Astrology is a group of systems, traditions, and beliefs which hold that the relative positions of celestial bodies (the Sun, Moon, and planets). Astrologers generally believe that the movements and positions of celestial bodies can inform them about events experienced on a human scale or that predictions can be made from them. Astrology is the NONSCIENTIFIC study of the sky and celestial bodies. Astrology Slide 3 Astronomy Astronomy is the SCIENCE of the universe in which the stars, planets, etc. are studied, including their origins, evolution, composition, motions, relative positions, and sizes. Slide 4 The patterns of stars seen in the sky are called constellations. The stars in a particular constellation may appear to lie close to one another, but this is an illusion. Stars that appear right next to each other in the sky may be quite far apart in reality, because they may lie at very different distances from Earth. The illusion occurs because we lack depth perception when we look into space, a consequence of the fact that the stars are so far away. The ancient Greeks mistook this illusion for reality, imaging the Earth to be surrounded by a great celestial sphere on which the stars lay. The Celestial Sphere Slide 5 Today, the concept of a celestial sphere is still useful for our learning about the sky, even though we know that Earth does not really lie in the center of a giant ball of stars. We give names to special locations on the imaginary celestial sphere. The point directly over the Earths North Pole is called the north celestial pole. The point directly over Earths South Pole is called the south celestial pole. The intersection of the Earths equatorial plane with the celestial sphere is called the celestial equator. The north celestial pole happens to be very near the bright star called the North Star, the Pole Star or Polaris. Slide 6 The terms declination, which is analogous to latitude, and right ascension, which is analogous with longitude, are used in the system of celestial coordinates that we use to pinpoint locations on the celestial sphere. Declination, like latitude, is the angular distance north or south of the celestial equator. Right ascension, like longitude, is the angular distance measured eastward along the celestial equator from the position of the vernal equinox. The vernal equinox is at the point in the sky where the sun crosses the celestial equator, at the onset of spring. Slide 7 The apparent annual path of the sun against the backdrop of the celestial sphere is called the ecliptic. The planets and the moon travel in nearly the same path as the sun along the ecliptic. Slide 8 The imaginary plane that connects Earths orbit with the celestial sphere is called the plane of the ecliptic. Because of the earths tilt (which is 23 degrees), the apparent path of the sun and the celestial equator intersect each other at an angle of 23 degrees. When the apparent position of the sun is plotted on the celestial sphere over a period of a years time, the path intersects the celestial equator at two points. From a Northern Hemisphere point of view, these intersections are called the vernal (spring) equinox (March 20-21) and the autumnal equinox (September 22-23). On June 21-22, the date of the summer solstice, the sun appears 23 degrees north of the celestial equator, and six months later, on December 21-22, the date of the winter solstice, the sun appears 23 degrees south of the celestial equator. Slide 9 We only see half of the celestial sphere at one time. The dome of stars that lies over us is called the local sky. The boundary between Earth and sky is called the horizon. The point directly overhead is called the zenith. Your celestial meridian is an imaginary half-circle stretching from your horizon due south through your zenith, to your horizon due north. Slide 10 You can find the position of any object in your local sky by stating its: direction along the horizon its altitude above the horizon When measuring altitude, your horizon is 0 degrees and your zenith is 90 degrees. Slide 11 A sextant is an instrument used to measure the altitude of objects from the horizon. For more precise astronomical measurements, we subdivide each degree into 60 arcminutes and subdivide each arcminute into 60 arcseconds. Slide 12 If you extend your hand to arms length, you can use your fingers to estimate angular distances and sizes in the sky. Your index finger is about 1 and the distance across your palm is about 10. Because of our lack of depth perception in the sky, we cannot tell the true sizes of objects or the true distances between objects just by looking at them. For example, the Sun and the Moon look about the same size in our sky, but the Suns diameter is actually about 400 times larger than the Moons diameter. We can measure angles in the sky. The angular size of an object is the angle it appears to span in your field of view. The angular distance between a pair of objects in the sky is the angle that appears to separate them. You can use an outstretched hand to make rough estimates of angles in the sky. Slide 13 Polaris Polaris, the north star or pole star, is special because it is so close to the north celestial pole. Contrary to relatively common belief, Polaris is not the brightest star in the sky. Polaris position makes it very useful in navigation, because it closely marks the direction of due north, and because its altitude in your sky is nearly equal to your latitude on Earth. Polaris is the alpha star in the constellation, Ursa minor (the little bear). The alpha star in a constellation is the brightest star in that constellation. Slide 14 Polaris can be located by looking north at an altitude equal to your latitude (East Views latitude is about 30 N). You can also use the two pointer stars in Ursa major, the big bear, that will point towards Polaris. The two pointer stars in Ursa major are called Merak and Dubhe. Slide 15 Earths rotation makes the celestial sphere appear to rotate around us. However, because we can only see half of the celestial sphere from any location on Earth, This simple motion looks more complicated in the local sky. In the Northern Hemisphere, stars seem to rotate around Polaris each day. All stars (and constellations) seem to rise and set from the horizon, except for five constellations. These five constellations, called the circumpolar constellations, circle around Polaris, but are high enough in the sky that they never set. This picture is taken with a long exposure and shows the movement of the circumpolar constellation during a nights period. Circumpolar Constellations Slide 16 The five circumpolar constellations are: Ursa major, Ursa minor, Draco, Cassiopeia, and Cepheus. Slide 17 The night sky changes throughout the year because of Earths changing position in its orbit around the Sun. The Ecliptic and the Zodiac As we orbit the Sun over the course of a year, the Sun appears to move against the background of the distant stars in the constellations. We do not see the Sun and the stars at the same time, but if we could we would notice the Sun gradually moving eastward along the ecliptic, completing one circuit each year. Slide 18 The constellations along the ecliptic are called the constellations of the zodiac. Tradition places 12 constellations along the zodiac, but the official borders include a wide portion of a thirteenth constellation, Ophiuchus. Slide 19 The 12 traditional constellations of the zodiac are: But why is there a range of time for the zodiac signs? Slide 20 If we could see stars in the daytime, the Sun would appear to have a constellation behind it. Remember that stars are much further away then the Sun, so the stars are actually beyond the Sun. For instance, if we could see the stars in the sky today during the day, we would notice that the constellation, Virgo, is behind the Sun. According to astrologers, the Sun is touching that constellation. Now, looking at the zodiac chart again, you will notice that the date range for Virgo is Aug. 24 th Sept. 23 rd. The reason for the date range is because Virgo is behind or touching the Sun during that time of year. The reason why the lengths of times vary is due to the sizes of the constellations and the time period it takes the Sun to move through it. Slide 21 Horoscopes and Zodiac Signs According to astrologers, when you were born, the Sun was touching or in the house of your zodiac sign. The Sun is considered a powerful object that can determine traits and personalities that you will have. And since it was touching your zodiac sign the day you were born, that constellation guides and governs your life. Again, this is according to astrologers (nonscientific people). Horoscopes are supposed predictions of future events. Slide 22 VIRGO August 24-September 22 Your ruling planet is Mercury and your element is earth. If you are a Virgo, you may be a bit of a perfectionist. You love to organize and plan and you thrive on hard work. You always need to have the last word and you can sometimes be oversensitive. Some compatible signs include Gemini, Pisces, and Taurus. So lets check this out. Do you think it is accurate? Slide 23 So why the change in the zodiac? Or did it really change? This change has apparently been coming throughout the years, as the 12 original signs were set almost 3,000 years ago. But the change over the years in the position of the earth in relation to the sun have created a need to revamp the astrological signs. At this point, we will have to see what really happens with this matter over the next few years. Right now, it doesnt really seem to be gaining many supporters. There is also the speculation that it will not affect the Western world or persons born before 2009. Slide 24 In Greek mythology, Ophiuchus was Aesclepius, Master Architect, Healer, and God of Wisdom. He has always been a part of the zodiac belt, but until now was never included in the Western astrological breakdown. As the story goes, Aesclepius was a Greek God of medicine and, when trying to bring Orion the Hunter back to life, was taken down by Zeus and cast to the sky with the Greek name Ophiuchus. Ophiuchus Slide 25 An asterism is a group of stars within a constellation that forms a recognizable figure used to find and identity the constellation. Asterisms are not constellations. Asterisms