Beginner's Guide to the Night Sky ABC Science Understanding the night sky was easy for ancient mariners and shepherds, but those of us living under light polluted skies not to mention a roof don't often see the stars.
Even when we do, the night sky can look like a random bunch of dots that's not exactly user friendly for beginners. So how do you make sense of what's going on up there? You just need to get your head around how the shape and movement of the Earth through space affects what part of the night sky you see which is a lot easier than it sounds! With a few basics under your belt you'll be totally across why and how stars move across the sky at night, where to coach outlet handbags coupons look for planets, why we can only see some constellations at certain times of the year and how your latitude affects which stars you can see at night. ^ to top The sky changes in one day You can gaze at the sky for five or ten minutes and nothing much will happen. But if you could speed the whole night up and watch the sky in fast motion you'd see plenty of action. You'd see the stars moving across the sky as one. Stars rise in the east and set in the west, just like the sun and moon do. The Earth spins from west to east, so everything in the sky comes into view as we spin towards it and leaves our view as we spin away from it. But, depending on where you are, not allstars rise and set. If you're in the southern half of Australia, looking south at the sky in fast motion, the stars there (including the Southern Cross) go around the sky in a circle, like in this animation. The stars aren't really circling a point in the sky we are. The point is the South Celestial Pole, the spot in the sky that lies directly above the South Pole. The Earth spins on an axis that runs from the North to the South Pole it's like we're turning on a giant imaginary skewer. If you look up at the sky from the North or South Pole, you'll always see the stars going in circles overhead, never rising or setting at the horizon. If you went to the equator you'd see something quite different. The equator lies at a right angle to the Earth's axis of spin, so every star rises in the east, goes straight across the sky and sets in the west with mathematical precision. The downside is you can't see the celestial poles or the stars circling around them because the rest of the planet is blocking your view. In between the poles and the equator at latitudes like southern Australia you are far enough south to see the stars circling the South Celestial Pole, but because you're not at a right angle to the axis of spin, the stars don't go straight overhead as they travel from east to west. Instead they travel at an angle from the ground, moving further north as they rise in the east, and further south as they set in the west (in the Northern Hemisphere, the stars curve towards south as they rise). Of course, the stars aren't the only things in the night sky you can usually see a planet or two as well. The planets (including Earth) all orbit the sun in roughly the same plane. From Earth it coach outlet purses using fire looks like the sun and all the planets follow an imaginary line in the sky called the ecliptic. That's great for star watchers because if you know where the sun travelled during the day, you know where to start looking for Jupiter, Saturn, Mars, Mercury and Venus at night. ^ to top The sky changes over a year The zodiac constellations travel in the same plane in the sky as the sun. As well as the daily turn of the planet, the Earth's annual orbit around the sun means we see slightly different sections of the universe every day. It also means we'll be coach outlet stores carlsbad back where we started in a year's time, looking at the same stretch of sky. If you look at the sky from the same place after just six months halfway through the Earth's solar orbit some of the constellations will still be there, some new ones will have appeared and others disappeared. The best way to get a handle on the regular rhythm of the stars appearing and disappearing is to look at the zodiac constellations. There are 12 zodiac constellations the ones we're all familiar with from astrology. Like the sun and the planets, the zodiac constellations all lie in the ecliptic, so they're visible from every place on Earth where you can see the sun rise and set. This explains why they feature so prominently in ancient cultures. The zodiac constellations span the entire sky, so we never face all 12 of them at once. If you look up on a dark night, you should be able to see at least four zodiac constellations at any one time, lying across the ecliptic. During the night, as the earth spins, each of these constellations will sink in the western sky, while others will rise in the east. All up, if you were to watch the sky for an entire night, you'd see up to ten of the twelve zodiac constellations. (The few that you can't see are in the area of the sky blocked out by the sun. See text box below.) So learning to spot the zodiac constellations, knowing what order they appear in (the same order given in horoscopes) and knowing where the ecliptic is, means you should be able to pick out an impressive four or more constellations that everyone's heard of. 'Star signs' and 'sun signs'If you've read a horoscope you might expect to see Sagittarius prominent in the November/December sky, and Leo in the July/August sky and so on, but this isn't the case. For example, you can't see Sagittarius in the night sky during mid December because at this time of year the sun is positioned between Earth and the constellation, blocking our view. The same goes for the rest of the zodiac constellations; ancient astrologers assigned each zodiac sign to the time of year when the sun blocks that constellation from our view. So your 'star sign' is actually your 'sun sign'. ^ to top Latitude affects your view of the sky As well as the Earth's position in space, the area of sky we can see at night is determined by how far north or south of the equator we are. Places at the same latitude see the same view of the night sky. So while Adelaide and the Chilean capital Santiago are separated by the Pacific Ocean, they see the same constellations at night because the Earth is spinning them past the same stretch coach outlet stores chicago of southern sky. But people living on the same longitude can see quite different skies. Residents of Adelaide and Tokyo are on the same longitude, and see some of the same parts of the sky the area around the ecliptic, like zodiac constellations and planets. But Tokyoites are too far north to see objects near the South Celestial Pole, like the Southern Cross.
And Adelaidians can't see things in the far Northern sky, like Polaris, the North Star. It's because the earth is spherical, and the bulge around its middle blocks the north and south extremes from view. Southern Sky SpecialtiesPeople in the Southern Hemisphere get an exclusive view of the Large and Small Magellanic Clouds two of our neighbouring galaxies that can identified with the naked eye and some of the brightest globular clusters spherical clumps of stars that orbit galaxies such as Omega Centauri in the constellation Centaurus and 47 Tucanae, in the constellation Tucanae (the Toucan).
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