Digital Universe Guide - Hayden Planetarium

More documents

Recommendations

Info

78 3. THE MILKY WAY ATLAS 3.3.5 Nearby Stars Group Name nearstars Reference Lépine Shara Proper Motion Catalog Sébastien Lépine & Michael Shara (AMNH) Prepared by Sébastien Lépine (AMNH) Labels No Files LSPMstars 100ly.speck Dependencies halo.sgi, colorbv.cmap Census 7,031 stars Critical toward our understanding of the Galaxy and the Universe are the stars that surround the Sun. If our knowledge of the local stellar population is inaccurate, then astronomer’s theories on stellar evolution are unsound. Furthermore, the locations of all stars, even the size and scale of objects in the Universe, rests upon the accuracy of the local stellar neighborhood. The Lépine Shara Proper Motion Catalog (LSPM) contains the most complete sample of stars within 100 light-years, with over 3,000 newly discovered stars. These stars have high proper motions, that is, they move across the night sky, as seen from Earth, relatively quickly. Of course, we do not see stars streaming across the sky: the fastest star in the sky, Barnard’s Star, moves only one-quarter of one degree (about half the width of the full Moon) per century. However, if we observe the same spot over a span of decades with a telescope, we will see the stars move in the sky. All stars are in motion within the Galaxy; the Sun orbits the center of the Milky Way galaxy at approximately 500,000 miles/hour. Some stars move alongside the Sun and appear to have little motion in the sky, other stars are moving at angles perpendicular the Sun, giving them higher proper motions. Barnard’s Star will be the closest star to the Sun around the year 11,700 AD, when it will be only 3.8 light-years distant. The new stars in this catalog were discovered by comparing images of the sky from two epochs. When astronomers analyze two images from the same patch of sky taken 50 years apart, the light from each pixel should match between the two images. If there is a bright spot in one image that is not in the other, then it is scrutinized to see if it’s a fast-moving star. Revealing the Unseen Most of the stars in this catalog are below the brightness limit of our eye, so how do we see them in the Digital Universe? We must represent them conceptually rather than photo-realistically. To see the dimmer stars, which represent the majority, we must increase their
3.3. MILKY WAY DATA GROUPS 79 luminosity scale in the Digital Universe. By default, the stars in this data set are 200,000 times their normal brightness and the halo on each star has an upper size limit of 20 pixels, so that the few bright stars in the 100-light-year-radius volume, like Sirius, do not overpower the rest of the stars with their brightness. To return these stars to their true brightness, use the commands slum /200000 and polymin 1 1e8 (in this order), then they will be on equal footing with the normal stars. Local Stellar Density The LSPM catalog contains over 7,000 stars. Viewing these stars 200,000 times brighter than their true luminosity reveals the sheer density of the local stellar neighborhood. For example, in the same 100-light-year-radius sphere, Hipparcos only observed 2,414 stars (Hipparcos was a targeted survey, so no new stars were expected to be discovered). Another, more informative, comparison is illustrated using the preset selection expressions. Selection Expressions for the Nearby Stars Alias Partiview Command Description eye thresh appmag -2 6.5 Select those stars visible to the unaided eye in the night sky lowlum thresh absmag 10 25 Select the intrinsically faint stars hip thresh hipid 0 130000 Select those stars with a Hipparcos ID nonhip thresh hipid < 0 Select all stars without a Hipparcos ID Let’s view the number of stars that are bright enough to see with our unaided eye using the eye selection expression. Type see eye and 577 of the 7,031 stars will remain. Perform the same exercise on the stars data group (activate stars and type see eye) and over 8,600 stars will remain. This tells us that over the course of one year there are about 8,600 “naked eye” stars in the night sky of both hemispheres. Only 577 of them are within 100 light-years. Therefore, about 6,500 nearby stars, right in our own astronomical backyard, remain invisible without the use of a telescope. To see the intrinsically dim stars, we can use the lowlum selection expression. Now we have over 4,600 dim stars in view. These are primarily cool, red stars that are ubiquitous throughout the Galaxy. While this catalog presents a more accurate representation of the local stellar density, fainter objects remain and astronomers are beginning to catalog them.
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 19 and 20:
Page 21 and 22:
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 and 34: 3.2. MILKY WAY ATLAS TUTORIAL 33 th
Page 35 and 36: 3.2. MILKY WAY ATLAS TUTORIAL 35 Op
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 77: 3.3. MILKY WAY DATA GROUPS 77 If yo
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 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 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 107 and 108: 3.3. MILKY WAY DATA GROUPS 107 righ
Page 109 and 110: 3.3. MILKY WAY DATA GROUPS 109 beyo
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 129 and 130:
3.3. MILKY WAY DATA GROUPS 129 3.3.
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?