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A Basic Guide to How the Cosmos Works (and what do all those funny abbreviations mean?). Bryan P Shumaker NOMAC. The Solar System. Our sun is the center of the solar system . It is about 93 million miles away.
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A Basic Guide to How the Cosmos Works (and what do all those funny abbreviations mean?) Bryan P Shumaker NOMAC
The Solar System • Our sun is the center of the solar system . It is about 93 million miles away. • This distance is called an “A.U.” (Astronomical Unit) and is often used as a unit of measurement • The planets rotate around the sun, mostly in the same plane and all in the same direction • Mercury, Venus, Earth, and Mars are considered the rocky planets
The Solar System • The asteroid belt is material left over when the solar system first formed and unable to form a planet due to the strong gravitational influence of Jupiter • Jupiter and Saturn are considered the gas giants • Uranus and Neptune are called the ice giants • Beyond Uranus is a vast cloud of objects (including Pluto) which make up the Kuiper Belt
The Solar System • Beyond the Kuiper Belt is a vast shell of icy bodies and proto comets which make up the Oort Cloud. • This extends out about one light year from the Sun
Distances • Because of the enormous distances in space, we refer to the distance as how far light will travel in a set period of time. Light travels at 300 million m/sec., or about 186,000 miles/sec. • The distance from the Sun to the Earth is about 8 light minutes • The distance from the Sun to Neptune is about 4.5 billion miles, or 30.1 AU, or about 4.2 light hours!
Solar System • The distance to the probable edge of our solar system is about 1.5 light years • The NEAREST star is just over 4 light years away • How do we measure distances to such far away objects?
Distance Measurement • One way to measure distance is by carefully measuring the change in angle to an object from two different points in space and use basic trigonometry. We take a picture and compare it with an identical picture taken 6 months later. The slight shift is measured in arc seconds (60 of which make 1 degree). This change in view, or parallax, is then used to calculate how far away an object is. The moon is about 0.5 degrees wide.
Distance Measurement • A measurement of one arc second’s worth of parallax change is called a “parsec” and works out to 3.26 light years • This system works well up to about 30 -40 light years—it becomes increasingly difficult to measure such tiny shifts beyond this distance
Distance Measurement • Cepheid Variables---These are a group of stars that vary in their brightness on a very consistent, periodic schedule. This variability is directly proportional to their luminosity. If you can measure the brightness and compare it to a star of known brightness, you can determine how far away that star is. • Okay for distances up to several million light years (need to be able to see individual stars of the distant galaxy)
Distance Measurement • Doppler shifting (Red Shift) • Light moving toward us is compressed and on a spectrograph (fancy prism), the light is shifted slightly towards the blue. If moving away, the light is shifted towards the red end of the spectrum
Distance Measurement • Everything in space is basically accelerating away from each other. The farther away an object is, the faster it is moving. This is a constant, uniform increase in both speed and distance, and is called the Hubble constant. • By measuring the amount of red shift, we are able to determine how far and how fast an object is moving away and at what distance. • At present , we can see objects almost 12.5 BILLION light years away—almost the time when it all began—the Big Bang.
Interstellar Space • This is the space between the stars and objects in our own galaxy • Our galaxy measures about 120,000 light years in diameter and contains approx. 300 -600 billion stars! We are about 60,000 light years from the galactic core • Our galaxy, which we call the Milky Way, is part of a larger cluster of galaxies called the Local Group
Common Terms • Cardinal Directions -- North, South, East, West
Common Terms • Altitude (Alt) -- The number of degrees an object is above the horizon. Ninety degrees is straight up • Azimuth (Az) -- The point where the object is closest to the horizon and is measured in degrees in a circle along the horizon, starting with North ( 0 or 360)
Common Terms • Celestial Equator-- Located on the Earth’s equator, but projected into space • Declination (Dec) -- The number of degrees the object observed is north or south of the Celestial Equator • Right Ascension (RA)-- Measured in hours along the Celestial Equator. It runs from 0 hours to 24 hours
Common Terms • Ecliptic—The plane of the Earth’s orbit around the Sun. This is about 23 degrees north of the true equator since the Earth is tilted about this amount off the vertical • Zenith—Directly above the observer • Meridian– An imaginary line connecting the north and south poles running directly overhead
Telescope Type Review • Refractor
Telescope Type Review • Reflector
Telescope Type Review • Cassegrain (multiple variants of this)
Eyepieces • The larger the size in mm, the less the magnification. A 24mm eyepiece gives less magnification than a 9mm one • Divide the focal length of the telescope by the eyepiece size=magnification • Multiple types—Orthos, Kellners, Plossls, Erfles, RKEs, Radians—the list goes on and on! • The cost varies from $30 to $800 PER EYEPIECE
Space Object Abbrev. • Many objects in space are described by a name, a number, or a combination of both. Some of the more well known ones have popular names used as well • M objects--named for Charles Messier, 18th century French comet hunter
Space Object Abbrev. • M1 through M110—A list of popular and relatively easy to find objects which include galaxies, open star clusters, globular clusters, planetary nebulae • QUICK NOTE—a globular cluster is a tight ball of stars which may contain up to 100,000 stars densely packed in a few light years. They are located above and below the galactic plane and are very old
Space Object Abbrev. • QUICK NOTE– A planetary nebula is actually a star that has blown off its outer layers as part of its death process • Globular cluster Planetary neb.
Space Object Abbrev. • Open Cluster– A group of stars that formed at about the same time and location and are loosely bound together by gravity • Double Star --The stars have to be physically interacting with each other and not just a line of sight chance arrangement • Nebula -- A collection of gas and or dust. Often they are large clouds of dust, gas and are stellar nurseries
Space Object Abbrev. • NGC-- stands for New Galactic Catalog • Arp -- named after Alton Arp,; describes irreg. galaxies • Greek letters used to designate prominent stars • HIP-- from the Hipparchos star catalog • B objects-- named after Barnard, describes clouds of dark gas and dust • Caldwell -- lists of certain galaxies • IC -- describes bright, glowing clouds of gas and dust
Space Object Abbrev. • There are several other specialized lists and types of objects • Almost all the objects viewable to amateur astronomers are in one of these lists and/or catalogs • For a great view of the different types of objects and categories, visit http://www.utahskies.org/deepskyIndex.shtml • Visit www.nomac.net for this link and many other useful ones