Introduction to AstronomyMike SwansonJanuary 2005

The Motion of the Sky

The Night SkyThis drawing created in Cartes du Ciel.This drawing created in TheSky.

The Solar System

Deep Space(Deep Sky Objects)StarsNebulaPlanetary NebulaStar ClustersGalaxiesBlack HolesQuasars

ResourcesMagazinesSky and TelescopeAstronomyIntroductory BooksExploring the Night Sky, Terence Dickinson (kids)Nightwatch, 3rd Ed., Terence DickinsonTurn Left at Orion, 3rd Ed., Consolmagno & DavisThe Binocular Stargazer, Leslie PeltierThe Night Sky, David ChandlerExploring the Night Sky with Binoculars, David ChandlerIntermediate BooksThe Backyard Astronomers Guide, Terence DickinsonAstronomy: A Self-Teaching Guide, 5th Ed., Dinah MocheMany of these books are found in the library, all can be purchased at www.skypub.comComputer SoftwareTheSkyStarry Night Backyard/ProSkyMap ProDeepSky2000Astronomy ClubsMeetings, Star PartiesLarge, club-owned scopes

ResourcesInternet - General AstronomySkyMaps.comwww.SkyPub.comwww.Astronomy.comwww.corvus.com -American Association of Amateur Astronomerswww.astroleague.org - Astronomical Leaguewww.EarthSky.com - Earth and Skywww.nasa.gov - NASA Main Sitenix.nasa.gov - NASA Image Exchangewww.ScopeReviews.comInternet - Online Storeswww.telescope.com - Orion Telescopewww.Astronomics.comwww.Adorama.comwww.OceansidePhotoAndTelescope.comwww.HandsOnOptics.comwww.Shutan.comInternet - Telescope Makerswww.Celestron.comwww.Meade.comwww.TeleVue.comwww.telescope.com - Orion Telescope

Clear Skies!

Astronomy is arguably humankind's oldest science. Historic and prehistoric accounts show that as long as humans have been recording things important to them, the sky has figured prominently. While we have been able to very accurately determine the motion of the objects in the sky for more than three thousand years, it is only a relatively recent development that we have come to understand why they move the way they do. Unfortunately, most folks still don't know the why and most don't even notice the motion!

After you spend a little time under the night sky you begin to notice things that were not immediately apparent. As the night passes, the various star patterns drift slowly overhead, coming up from the east and setting in the west. The stars differ in brightness and seem to form recognizable patterns. Some nights are clearer than others, even comparing various nights with no clouds. Occasionally a bright light passes overhead unexpectedly. Night after night the phase and location of the Moon changes dramatically. There is a lot to be seen if you are observant. At first it can be quite confusing, but there are some simple concepts that can help as you slowly start to make sense of it all. Each day the Earth rotates approximately one full turn (360 degrees) about its axis. Naturally this is what cause the sun and stars to move across the sky. Once each year, the Earth completes a revolution around the Sun. This makes it so that the stars we can see each night change from season to season. On the same day each year the night sky will look virtually the same. The Earth is tilted about 23.5 degrees from the plane of its orbit (path) around the Sun, this is what causes the seasons. When the part of the Earth you are on is tilted towards the sun, the more direct rays heat more and you experience summer.

The night sky is divided into different areas - similar to how the Earth is divided into countries. These areas are known as the constellations. The Sun, Moon and all of the planets travel through only 12 of the constellations - the Zodiac.Measuring in the sky degrees - 60 minutes in deg, 60 seconds in minute. Degrees: fingertip - 1, 3 fingers - 5, fist - 10.RA and Dec, like long/lat on Earth. All objects can be located by RA/Dec.Magnitudes - lower numbers brighter, negative numbers are brightest. Naked eye in dark location - mag 6 - 1000s of stars, binos - mag 9 >100,000 stars, 4 in. scope - mag 12 > a million stars. Extended objects like nebula are measured in total magnitude - all the light gathered to a point - surface brightness still low. Seeing Conditions: Seeing Transparency Light pollutionObservation Technique: Dark adaptation Averted vision Move/shake the binos/telescope Try different magnifications Spend time studying an object to bring out detailSun - one of the billions of stars in our galaxy - the Milky WayMoon - Earths only natural satellite, approx 1/4 mil miles from Earth, same side always faces Earth, the gravity of the Moon and to a lesser extent the Sun cause ocean tides.Mercury - Inner planet, 1/3 diameter of Earth, temperatures as hot as 350C, surface covered with craters.Venus - Inner planet, very similar in size/mass as compared to Earth, temperatures as hot as 480C - hottest in the solar system.Mars - First of the outer planets, a little bigger than high the size of Earth, home of the tallest mountain (25km), and the longest valley (4000km) in the S. S.Asteroid Ida and its moon - one of thousands of asteroids in the asteroid belt.Leonid Meteors - One of the several regular meteor showers appearing regularly each year. Small bits of dust and sand.Gas Giants - mainly made of Hydrogen and Helium gas:Jupiter and one moon of its more than 20 moons - Largest planet in S. S. more than 100 times the diameter and 300 times the mass of the Earth. Great Red Spot is a storm that has been raging for more than 400 years and is 3 times the size of the Earth!Saturn - Rings are visible in even small telescopes, takes more than 29 years to make a trip around the Sun.Uranus - 84 years to make a trip around the Sun, rotational axis nearly parallel with orbital plane.Neptune - 165 years to make a trip around the Sun, the dark spot is a storm similar to Jupiters.Outer Solar System: Pluto and its moon Charon - 1/5 size of Earth, temperature -24 C, highly eccentric orbit sometimes it inside Neptune's orbit.Comet Hale-Bopp - one of the most spectacular comets of the 20th Century. Frozen ball of ice and rock, tale is swept away from the Sun by solar wind (radiation coming from Sun).Spacecraft Voyager - Sent the images of the Gas Giants: Jupiter through Neptune. Still sending back data more than 20 years later, Voyager is the fastest manmade object in existence.Kuiper Belt - Beyond Pluto containing asteroids and short period comets.Oort Cloud - A shell surrounding the solar system, extremely long period comets and other small, icy bodies.Stars: different colors due primarily to temperature, some are binary/multiple, some are variable, designations - Bayer (Greek alpha by constellation), numbered by constellation, HD - Henry Draper, SAO - Smithsonian Astrophysical ObservatoryNebula: generally clouds dust and gas, often lit by stars in the cloud. Also, some clouds of dust form dark nebula.Planetary Nebula: not a planet at all, rather a star that went nova - exploded. The nebulosity is actually glowing gas blown off during the explosion.Star Clusters: groups of stars moving together through space. Two types: open and globular. The globular clusters are very old and mostly arranged the outside edges of galaxies. Open clusters are usually quite young and slowly drifting apart.Galaxies: groups of billions and billions of stars. The universe has billions of galaxies.Black Holes: massive amounts of matter packed into an extremely small space. The gravity is so intense, even light cannot escape. There are small black holes which are basically collapsed giant stars and then there are unimaginable huge black holes that are located in the hearts of most galaxies.Quasars: energy sources located around the universe that sometimes emit more more energy than the entire galaxy they are located in. Thought to be massive black holes pulling in huge amounts of matter from the surrounding galaxy. As the matter accelerates into the black hole, much of it is converted to energy.Astronomers have identified nearly 10,000 galaxies in this 275-hour exposure taken by the Hubble Space Telescope. The faintest of these galaxies are 12 billion light-years distant. That means the light we are seeing was created 12 billion light-years in the past. The universe is about 13.7 billion years old, so these most distant galaxies are some of the first that formed. This image is just a tiny section of the night sky a grain of sand held at arms length.