Digital Universe Guide - Hayden Planetarium

More documents

Recommendations

Info

34 3. THE MILKY WAY ATLAS Relate this to Earth by turning on the equatorial coordinates, radec. These are Earth’s coordinates projected onto the sky. The bright line is the celestial equator, and the poles (where the lines converge) are those parts of the sky directly over the poles on Earth. From mid-northern latitudes, we see from about −40 ◦ to +90 ◦ declination throughout the course of the year. Notice the difference between the Milky Way visible in the Northern Hemisphere and that part visible at southern latitudes. The southern Milky Way is much brighter and more beautiful. Globular Clusters Are Mostly Near Galactic Center Let’s perform the same experiment that the astronomer Harlow Shapley did 80 years ago. Born in 1885, Shapley was studying the sky at Mount Wilson Observatory outside Los Angeles when the country was involved in World War I. Wartime blackouts in the city provided astronomers an opportunity to see the sky without the lights of the city below. Shapley had been looking at the globular clusters in the sky for some time. Turn on the globular clusters, gc, scan the sky, and see if you notice anything odd about where they are located. See anything strange? Look toward the star Sirius, then look toward the opposite side of the sky along the Milky Way. It’s easy to see that most of the clusters are found around the bright part of the Milky Way. From this, Shapley deduced that the center of our star system must be in this direction. By estimating the distance to these clusters, he put to rest the debate about the size and structure of our Galaxy. We’ll revisit this in three dimensions later in these tutorials. Earth lies within the disk of the Galaxy, making it difficult for astronomers to understand the structure of our star system. Not until astronomers began seeing the Milky Way in wavelengths outside the visible spectrum did the structure of the Galaxy become apparent. Tutorial: Two-Dimensional Distributions Goals: View various data sets from Earth’s perspective to see what they reveal about the Galaxy. Before starting, turn on: stars, mwVis, gc You will be using: oc, ob, pul, pn, h2, snr You’ve seen the distribution of the globular clusters in “The Milky Way from Earth,” now let’s investigate other data sets for similar trends.
3.2. MILKY WAY ATLAS TUTORIAL 35 Open Clusters Are Found in the Band of the Milky Way With the globular clusters on (gc), turn on the open clusters with the oc button. Open clusters are less dense, younger star clusters. In the Atlas, they are represented by green points. By turning off the stars group, you have a clear view of the two types of clusters. You can make things even clearer by turning off the clusters’ labels. Make oc the active data group and press the Label Toggle Button. Once you’ve turned off the labels for both data groups, it becomes apparent that the open clusters are concentrated in the Galactic disk, while the globulars are found mainly in one part of the sky. This concentration of open clusters in the disk led astronomers to call them Galactic clusters. Since gaining a wider perspective on our Galaxy and the surrounding <strong>Universe</strong>, astronomers have since turned to calling them open clusters, a name that refers to the more spread-out nature of the stars within them. Open Clusters Are Younger Than Globular Clusters This spatial distinction between open and globular clusters reveals a story of Galactic structure and evolution. Open clusters are filled with younger stars and, therefore, are found in regions of the Galaxy where star formation occurs. Globular clusters are filled with older stars that formed very soon after the Galaxy was born. In our Galaxy, star formation occurs in the spiral arms within the disk. The gas in the disk condenses to form stars, some of which are massive enough to explode in supernovae, thereby triggering new stars to form by compressing the surrounding gas. The older stellar population is found in the spherical component of the Galaxy, often called the halo. Most of the stars in the halo are cool, dim stars that are spherically distributed around the Galactic center. What Do Other Data Sets Tell Us About the Galaxy? Let’s turn on another data set, ob, that shows the locations of bunches of stars called OB associations. These contain from tens to hundreds of stars and, as you can see, lie in the plane of the Galaxy. Again, these are filled with younger stars, as the associations last only a few tens of millions of years before drifting apart into individual stars. Turn on the rest of the 3-D data groups: pulsars, pul, planetary nebulae, pn, star-forming regions, h2, and supernova remnants, snr. Aside from the star-forming regions (called H ii regions), which signal stellar birth, the rest of these signify stellar death. H ii regions, in a sense, are at the beginning of the stellar life cycle. These give birth to open clusters and OB associations, which eventually die to become planetary nebulae, pulsars, or supernova remnants. Because these are connected to the stellar
Page 1 and 2: The Digital Universe Guide Brian Ab
Page 3 and 4: Contents Contents 3 List of Tables
Page 5 and 6: List of Tables 2.1 Log and Linear F
Page 7 and 8: 1.2. GETTING HELP 7 1.2 Getting Hel
Page 9 and 10: 1.5. ACKNOWLEDGMENTS 9 1.5 Acknowle
Page 11 and 12: 2.2. LAUNCHING THE MILKY WAY ATLAS
Page 13 and 14: 2.3. LEARNING TO FLY PARTIVIEW 13 T
Page 15 and 16: 2.3. LEARNING TO FLY PARTIVIEW 15 M
Page 17 and 18: 2.4. PARTIVIEW’S USER INTERFACE 1
Page 23 and 24: 2.5. DIGITAL UNIVERSE FILES 23 File
Page 25 and 26: 3.1. MILKY WAY ATLAS OVERVIEW 25 3.
Page 27 and 28: 3.2. MILKY WAY ATLAS TUTORIAL 27 3.
Page 29 and 30: 3.2. MILKY WAY ATLAS TUTORIAL 29 Wi
Page 31 and 32: 3.2. MILKY WAY ATLAS TUTORIAL 31 Yo
Page 33: 3.2. MILKY WAY ATLAS TUTORIAL 33 th
Page 39 and 40: 3.2. MILKY WAY ATLAS TUTORIAL 39 co
Page 41 and 42: 3.2. MILKY WAY ATLAS TUTORIAL 41 li
Page 45 and 46: 3.2. MILKY WAY ATLAS TUTORIAL 45 In
Page 47 and 48: 3.2. MILKY WAY ATLAS TUTORIAL 47 No
Page 49 and 50: 3.2. MILKY WAY ATLAS TUTORIAL 49 Th
Page 51 and 52: 3.2. MILKY WAY ATLAS TUTORIAL 51 to
Page 53 and 54: 3.2. MILKY WAY ATLAS TUTORIAL 53 st
Page 55 and 56: 3.2. MILKY WAY ATLAS TUTORIAL 55 th
Page 57 and 58: 3.2. MILKY WAY ATLAS TUTORIAL 57 bi
Page 59 and 60: 3.2. MILKY WAY ATLAS TUTORIAL 59 in
Page 63 and 64: 3.2. MILKY WAY ATLAS TUTORIAL 63 mo
Page 65 and 66: 3.2. MILKY WAY ATLAS TUTORIAL 65 fa
Page 67 and 68: 3.3. MILKY WAY DATA GROUPS 67 Earth
Page 69 and 70: 3.3. MILKY WAY DATA GROUPS 69 Data
Page 71 and 72: 3.3. MILKY WAY DATA GROUPS 71 The l
Page 73 and 74: 3.3. MILKY WAY DATA GROUPS 73 3.3.3
Page 75 and 76: 3.3. MILKY WAY DATA GROUPS 75 3.3.4
Page 77 and 78: 3.3. MILKY WAY DATA GROUPS 77 If yo
Page 79 and 80: 3.3. MILKY WAY DATA GROUPS 79 lumin
Page 81 and 82: 3.3. MILKY WAY DATA GROUPS 81 not p
Page 83 and 84: 3.3. MILKY WAY DATA GROUPS 83 Two p
Page 85 and 86:
3.3. MILKY WAY DATA GROUPS 85 expre
Page 87 and 88:
3.3. MILKY WAY DATA GROUPS 87 marke
Page 89 and 90:
3.3. MILKY WAY DATA GROUPS 89 brigh
Page 91 and 92:
3.3. MILKY WAY DATA GROUPS 91 3.3.1
Page 93 and 94:
3.3. MILKY WAY DATA GROUPS 93 inclu
Page 95 and 96:
3.3. MILKY WAY DATA GROUPS 95 old.
Page 97 and 98:
3.3. MILKY WAY DATA GROUPS 97 centi
Page 99 and 100:
3.3. MILKY WAY DATA GROUPS 99 3.3.1
Page 101 and 102:
3.3. MILKY WAY DATA GROUPS 101 3.3.
Page 103 and 104:
3.3. MILKY WAY DATA GROUPS 103 heat
Page 105 and 106:
Page 107 and 108:
3.3. MILKY WAY DATA GROUPS 107 righ
Page 109 and 110:
3.3. MILKY WAY DATA GROUPS 109 beyo
Page 111 and 112:
Page 113 and 114:
Page 115 and 116:
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
3.3. MILKY WAY DATA GROUPS 121 Othe
Page 123 and 124:
3.3. MILKY WAY DATA GROUPS 123 abou
Page 125 and 126:
3.3. MILKY WAY DATA GROUPS 125 Obje
Page 127 and 128:
Page 129 and 130:
Page 131 and 132:
Page 133 and 134:
Page 135 and 136:
Page 137 and 138:
Page 139 and 140:
Page 141 and 142:
3.3. MILKY WAY DATA GROUPS 141 this
Page 143 and 144:
3.3. MILKY WAY DATA GROUPS 143 Not
Page 145 and 146:
4 The Extragalactic Atlas The word
Page 147 and 148:
4.1. EXTRAGALACTIC ATLAS OVERVIEW 1
Page 149 and 150:
Page 151 and 152:
Page 153 and 154:
4.2. EXTRAGALACTIC ATLAS TUTORIAL 1
Page 155 and 156:
Page 157 and 158:
Page 159 and 160:
Page 161 and 162:
Page 163 and 164:
Page 165 and 166:
Page 167 and 168:
Page 169 and 170:
4.3. EXTRAGALACTIC DATA GROUPS 169
Page 171 and 172:
Page 173 and 174:
Page 175 and 176:
Page 177 and 178:
Page 179 and 180:
Page 181 and 182:
Page 183 and 184:
Page 185 and 186:
Page 187 and 188:
Page 189 and 190:
Page 191 and 192:
Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Page 199 and 200:
Page 201 and 202:
Page 203 and 204:
Page 205 and 206:
4.4. OPTIMIZING THE EXTRAGALACTIC A
Page 207 and 208:
Appendix A Light-Travel Time and Di
Page 209 and 210:
Appendix B Parallax and Distance On
Page 211 and 212:
absolute magnitude M, can be calcul
Page 213 and 214:
discovered that there was a linear
Page 215 and 216:
Appendix D Electromagnetic Spectrum
Page 217 and 218:
Appendix E Constants and Units In a
Page 219 and 220:
Metric Prefixes These prefixes are
Page 221 and 222:
INDEX 221 center command, 50, 61 cl
Page 223 and 224:
INDEX 223 Earth’s radio signals,
Page 225 and 226:
INDEX 225 irregular galaxy, 147, 17
Page 227 and 228:
INDEX 227 entering, 21 every, 206 j
Page 229:
INDEX 229 stellar distance uncertai
show all

Digital Universe Guide - Hayden Planetarium

Create successful ePaper yourself

Delete template?

Save as template?