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Lesson 5: Star Designations, Right Ascension / Declination & Deep Sky Objects

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Lesson 5: Star Designations, Right Ascension / Declination & Deep Sky Objects LESSON 5: STAR DESIGNATIONS, RIGHT ASCENSION / DECLINATION & DEEP SKY OBJECTS What you will need: • Celestial Sphere globe • Planetarium Software (Cartes du Ciel: http://www.stargazing.net/astropc/) • Celestial Sphere video (http://www.starlight-theatre.ca/CS-VIDEO.HTM) • A copy of the handouts for each student. Suggested Outline: • Discuss star common star designations - Bayer, Flamsteed. (Beginner’s Observing Guide pg. 23) o Use planetarium software to show designations in use. o Point out Greek alphabet at back of Beginner’s Observing Guide (pg 194) • Discuss RA / DEC location system. o Use Celestial Sphere globe (or planetarium program) to illustrate RA/DEC system. Concentrate on explaining that the coordinates are locked into place on the celestial sphere, each star has its own “address”. It is more important for the students to understand this than it is to understand exactly how the system works. Demo on planetarium software how this makes finding objects easier than the alt-az system from different locations around the globe. o Hand out Equatorial Coordinates Systems article. • Watch the Celestial Sphere video (part on deep sky only. min 30 to min 40) • Discuss different types of deep sky objects. o Show file "#5 – Deep Sky Objects definitions" on a data projector (or use overheads provided) and discuss. o Hand out The Deep Sky Objects article. o Hand out Skyways pgs 76 through 80. o You can visit SEDS Messier website. http://seds.lpl.arizona.edu/messier/ to view more types of objects. • Show unlabeled slides (1 – 12) of deep sky objects in file "#5 – Object Identification". These have been drawn to try and approximate what would be seen through a telescope. Hand out notes pages of unlabeled slides. Have students write down beside each image what type of object they are. Then go over the next set of slides (14 – 25) with the answers on them. • Discuss how to read the charts the students printed out for homework from the Mag-7 Star Atlas Project. Between Class Assignments: o Read Beginner’s Observing Guide chapters 5 and 6 Names of Stars o Observe from ETUC Deep Sky Objects section Deep Sky Objects: refers to objects in the sky other than solar system objects (planets, comets, asteroids) and stars (single and multiple). Types of Deep Sky Objects: This list only covers the basic Deep Sky Objects which can easily be seen in small telescopes. For a more complete list and detailed information read an article called “The Deep Sky Objects” by Skyhound. http://www.skyhound.com/sh/dso_guide.html Star Clusters • Open clusters and Globular clusters Nebulae • Bright Nebulae – Emission and Reflection • Dark Nebulae • Planetary Nebulae Galaxies Open Cluster: a loose collection of stars that formed approximately at the same time from the same interstellar molecular cloud. Doug Wayland Comet Machholz & Double Cluster RASC: Prince George Centre Globular Cluster: a large, massive densely populated and very old group of stars that are gravitationally associated with each other. Beginner’s Observing Guide Brian Battersby Globular Cluster, M14 RASC: Prince George Centre Nebula: a diffuse structure composed of interstellar gas and dust. There are several types of nebulae. Emission Nebulae glow somewhat as do neon light, as they re-emit energy originally produced by nearby stars. Absorption Nebulae appear dark as they block the light from stars behind them. Reflection Nebulae are dark clouds of gas and dust that have been illuminated by reflected, rather than absorbed and re-emitted light, from nearby stars. Planetary Nebulae are the glowing shells of gas that have been ejected from an unstable star at a certain stage in its evolution. In the past, the disk-like appearance of such nebulae reminded astronomers of planets, when they were seen in in their telescopes, though they are not planets in any way. Beginner’s Observing Guide Bright Nebulae in Orion. Doug Wayland Emission (red) and reflection (blue) RASC: Prince George Centre Doug Wayland Horsehead Nebulae in Orion (dark nebula) RASC: Prince George Centre Dumbbell Nebula (planetary), M27 Ring Nebula (planetary), M57 Brian Battersby RASC: Prince George Centre Galaxy: a very large, grouping or collection of stars, much more massive than a globular star cluster. At one time galaxies were called “nebulae,” a term now used for massive conglomerations of gas and dust. Beginner’s Observing Guide Edge-On Spiral Galaxy, NGC 891 Brian Battersby - RASC: Prince George Centre Andromeda Galaxy (spiral), M31 Doug Wayland - RASC: Prince George Centre Nebula Open Cluster M13 - Globular Cluster Spiral Galaxy Planet Double Star M87 - Elliptical Galaxy Open Cluster Globular Cluster Planet Open Cluster & Nebula Eps Lyra Double Star (2 sets) Comet Hyakutake (by Scott Young) M1 – Supernova Remnant (by Scott Young) M42 – Nebula (by Scott Young) M65, M66, NGC 3628 – Galaxies (by Scott Young) M78 - Diffuse Reflection Nebula (by Scott Young) M80 – Globular Cluster (by Scott Young) M109 – Spiral Galaxy (by Scott Young) Belmont Society images courtesy of Bill Wiegert http://www.belmontnc.4dw.net/ Other eyepiece drawings by Scott Young of the Winnipeg Centre Student Handouts Equatorial Coordinates System by Robin Riordan, Prince George Centre In lesson three we learned about locating the positions of stars by their altitude and azimuth. This is generally referred to as the alt-azimuth coordinate system. If you had a chance to observe some stars during the course of a night you may have noticed that both the azimuth and the altitude of the stars change as the night wears on. The alt- azimuth coordinate system uses the Earth's horizon as a reference. But each observer, at a different latitude and longitude, has a different horizon. It is difficult for an astronomer in Roswell, New Mexico to share observations with another in Prince George, British Columbia. x Above is a diagram of the Earth with lines of latitude and longitude superimposed. Each place on the Earth is specified by its latitude (north south) and longitude (east west). Notice the “x” in the picture. This is Houston, Texas. The yellow number 30 represents 30 degrees latitude (north). The green number corresponds to about 90 degrees longitude west of the prime meridian near London. That coordinate (30, 90) is pinned onto Houston. So, anyone, anytime, can find Houston by going to that coordinate. In just the same manner astronomers have created a latitude and longitude system for the stars. But astronomers have given them different names. Declination corresponds to the concept of latitude. Right Ascension corresponds to the concept of longitude. Lets look at a star chart. 1 Polaris (north star) is in the center. The numbers going around the circle are right ascension (like longitude). Unlike longitude, which is measured in degrees, right ascension is measured in hours in a clockwise direction. It makes sense. Think of the sky as a big clock face with 24 hours instead of 12 hours. Now, the numbers that you see on the left, starting at 0 and moving inward toward to center, that is, 0, 20, 40, 60, 80, represent declination (like latitude). Polaris has a declination of 90 degrees. In a similar fashion to the Earth's latitude and longitude system, this coordinate system is pasted to the sky. The big star (I drew it larger than it actually is), toward the left edge of the picture, is called Castor. It is part of the constellation Gemini, the twins (see the twin stick figures?). Very roughly speaking Castor is at right ascension 8 hours, and declination 30 N ( N for north) degrees. So, (8,30) specifies where Castor is in the sky. That number is tacked onto the star. Even as the stars move through the sky during the course of the night their right ascension and declination numbers move with them. It's no different than roulette. The wheel spins and the numbers move with the wheel. We now have a coordinate system that is fixed to the stars. Each star has its own address (coordinate). Robin Riordan For another article on this topic see Nick Strobel’s Astronomy Notes at http://www.astronomynotes.com/nakedeye/s6.htm 2 1 2 3 4 5 6 7 8 9 Nebula Open Cluster 10 M13 - Globular Cluster Spiral Galaxy 11 Planet Double Star 12 M87 - Elliptical Galaxy Open Cluster 13 Globular Cluster Planet 14 Open Cluster & Nebula Eps Lyra Double Star (2 sets) 15 Comet Hyakutake (by Scott Young) M1 – Supernova Remnant (by Scott Young) 16 M42 – Nebula (by Scott Young) M65, M66, NGC 3628 – Galaxies (by Scott Young) 17 M78 - Diffuse Reflection Nebula (by Scott Young) M80 – Globular Cluster (by Scott Young) 18 M109 – Spiral Galaxy (by Scott Young) Belmont Society images courtesy of Bill Wiegert http://www.belmontnc.4dw.net/ Other eyepiece drawings by Scott Young of the Winnipeg Centre 19 The Skyhound's Guide to Finding Comets Page 1 of 6 The Deep Sky Objects What is a deep sky object? Generally speaking it's any object in the sky that isn't a star or in our solar system. Most deep sky objects are faint, diffuse and require a telescope to see. They make for spectacular photographs but often appear as little more than a faint smudge of light to your eye, even as seen through a large telescope. Deep sky objects break down into several categories: Open Star Clusters Globular Star Clusters Diffuse Nebulae Dark Nebulae Planetary Nebulae Supernova Remnants Galaxies Galaxy Groups Quasars Gravitational Lenses Open Star Clusters These are loose groupings of many stars. Some open clusters are large and spread out. For instance, the Hyades, Pleiades and the Beehive are all open clusters that you can see with your naked eye. Others are small and faint. If the stars are very faint the cluster may look more like a hazy patch of sky in your telescope rather than individual stars.
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