Digital Universe Guide - Hayden Planetarium

More documents

Recommendations

Info

152 4. THE EXTRAGALACTIC ATLAS increased. This acceleration is attributed to something astronomers call dark energy. Dark energy is the mysterious force that is causing the expansion of the Universe to speed up, overcoming the force of gravity. In 1998, astronomers looked at Type Ia supernovae—exploding stars with predictable brightness—and found that supernovae observed in distant galaxies were dimmer than they should have been, meaning they are farther than predicted and the Universe must be expanding faster than previously thought. Astronomers don’t know what dark energy is, but they do know some force is overcoming the gravitational pull within the Universe, speeding up its rate of expansion. For the Digital Universe, we use this information to compute distances to the galaxies and quasars in the Extragalactic Atlas. This provides you with the size and scale of the Universe at the present epoch. This distance scheme sets the scale of the Universe so that the quasars can be found past 20 billion light-years, while the CMBR is fixed to a sphere with a radius of 42 billion light-years. Of course, these objects were much closer when their light left. If we plotted the Universe according to where an object’s light left from, then the CMBR would be 13.7 billion light-years away. However, we have opted to plot the Universe at its current state, lending reality to the Atlas and one’s impression of the Universe. 4.2 Extragalactic Atlas Tutorial While the topics of astrophysics and cosmology are more complex in the extragalactic realm, the tutorials are less elaborate than those in the Milky Way Atlas. The homogeneity of the data at this scale, where we are limited to discussing galaxies as single objects, puts constrains on the types of data sets we have, as opposed to the zoo of objects one finds in the Milky Way. Our tutorials will take you on a journey from the Galactic neighborhood out to the edge of our observable Universe. Along the way, we will discuss scale and structure in the Universe. Let’s start by exploring our Galactic backyard. 4.2.1 Tutorial: The Galactic Neighborhood Goals: Explore the Milky Way’s nearest neighboring galaxies. Before starting, turn on: galaxy, local You will be using: cb command
4.2. EXTRAGALACTIC ATLAS TUTORIAL 153 In our first tutorial, you will explore the Galactic neighborhood, discovering what lies outside our Galaxy and how these objects are arranged around us. Let’s launch the Extragalactic Atlas and begin exploring. Starting from Home Upon launching the Atlas, you are just outside the Milky Way looking back on our home Galaxy. The image you see beside the Home label is not our Milky Way but NGC 1232, a galaxy that is believed to resemble the Milky Way. Barely detectable from this distance is the Point of Interest marker, the multicolored Cartesian axes that mark the location of the Sun and its planets within our Galaxy. Each half-width is 1,500 light-years, about the distance to the Orion Nebula. You may have to fly in closer to see the axes clearly. Begin by slowly orbiting this point where the Sun is located. You will notice some nearby galaxies with large labels and other, more distant galaxies that appear as green points. Focus on those near the Milky Way. At Partiview’s Command Line, type cb on to temporarily remove the more distant galaxies. Our Nearest Neighbor The nearest object to the Milky Way was discovered in 1994. The Sagittarius galaxy is represented by a point, but this belies the nature of this mysterious object. You may have figured out that the object is called Sagittarius because it is seen in that constellation in the night sky. However, parts of this galaxy have been seen on both sides of the Galactic disk. So representing it with one point is really not too accurate. The Sagittarius is a dwarf spheroidal galaxy that has been stretched and warped by our Milky Way. A dwarf spheroidal (dSph) galaxy appears as a smudge on the sky in even the largest telescopes. With a low star density, these galaxies often resemble star clusters rather than galaxies. The first dSph, Sculptor, was discovered in 1938 by Harlow Shapley. Astronomers have come to realize that galaxies interact with one another more often than once thought. The Sagittarius dSph is in fact in the midst of an interaction. As it orbits our Milky Way, our Galaxy slowly rips the Sagittarius dSph apart, stripping away streams of stars on each pass near the Milky Way’s disk. The same thing once happened with two other nearby companions, the Large and Small Magellanic Clouds.
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 37 and 38:
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 43 and 44:
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 61 and 62:
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:
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:
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:
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 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: 4.1. EXTRAGALACTIC ATLAS OVERVIEW 1
Page 151: 4.1. EXTRAGALACTIC ATLAS OVERVIEW 1
Page 155 and 156: 4.2. EXTRAGALACTIC ATLAS TUTORIAL 1
Page 169 and 170: 4.3. EXTRAGALACTIC DATA GROUPS 169
Page 203 and 204:
4.3. EXTRAGALACTIC DATA GROUPS 203
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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?