Overview of the Solar Journey Project:

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1 Overview of the Solar Journey Project: Visualization for Virtual Astronomy Andrew J. Hanson and Priscilla C. Frisch Computer Science Department, Indiana University and Dept. of Astronomy and Astrophysics, University of Chicago Principal programmer: Philip Chi-Wing Fu, Indiana Univ. 1

2 OUTLINE Modeling: Extraction of graphics models from Astrophysical data sources Visualizing: Creating viewable graphics representing the graphics models. Viewing: Keeping Sixty Orders of Magnitude in view is a challenge! Navigating: Roam across large scale ranges, but keep track of where you are... 2

3 ANIMATIONS Solar Journey Local view of objects important for understanding the environment of our ownsun.(4:00min) Cosmic Clock Global view of the Universe: how to visualize size of Universe using the timestamped light received at one moment on Earth. (3:35 min) 3

4 Modeling Astronomical Objects Features of Sun and Planets Viewing Stars: Positions and Motions Gas Clouds: Distance Editing Tool Adjusting and Aligning Objects and Images Viewing Galaxies 4

5 Modeling the Solar System Outer Planets and Solar Wind Need Orrery/Ephemeris models for absolute and relative motion 5

6 Modeling Astronomical Objects: Stars Viewing the Hipparcos catalog 6

7 Stars as Modeled Objects How do we model stars? Catalog Data. From catalogs like the Hipparcos Satellite catalog, we extract abstract types, color signature, location and distance. Reverse Engineer Color and Intensity. The properties go into a lookup table predicting the optical features from the abstract types. Reverse Engineer Optical Image. Impose a texture with features of atmospheric blur and telescopic instruments to make it look real Use 1=r correct. 3D flying requires nearby stars to look different than they look from Earth; use absolute magnitude. 2 Allow Sensitivity Adjustment. Very distant views are too faint adjust film sensitivity of simulated telescope. 7

8 Modeling Stars The Galactic Center focuses on the constellation Scorpius. 8

9 Modeling Stars Constellation outlines seen from Earth: pick and identify well-known stars. 9

10 Modeling Stars Many stellar velocity fields are known. 10

11 Modeling Stars Constellations from Earth 11

12 Modeling Stars Constellations viewed from 100pc away. 12

13 Modeling Stars 100 pc from the Sun: 3D stars with red distance error measures. 13

14 Modeling Stars Most distant measurable 3D distances: 1000 pc 14

15 Modeling Stars But these distances are terribly inaccurate! 15

16 Modeling Astronomical Objects Local Gas Clouds How do we model clouds? Distance Editing Tool. Uses direct and indirect information about absorption of light reaching Earth. Theory gives Expected Star Features. Deficiencies in expected light imply existence of dust in intervening gas clouds. Reverse Engineer Gas Density. Skilled astronomer can adjust cloud density using multiple evidence sources. Compute Cloud Thickness. Thicker or denser cloud gives more light absorption. Adjust Distances for Local Agreement. This generates a surface triangulation for front and back cloud surface model. 16

17 Modeling Local Gas Clouds Flattened View of local stars 17

18 Modeling Local Gas Clouds Spherical projection of gas surface. 18

19 Modeling Astronomical Objects Adjustment and Alignment How do we compose multiple data sources? Alignment Tool. Takes guide objects, usually stars, and adjusts unregistered 2D images to match the sky. Examples: Optical data: Nebulae. Examples: Spectral data: Star creation activity, supernovae, etc. Examples: Large Scale Spectral Data: Evidence for nearby supernovae ( Loops ) in IR and UV. 19

20 Aligning Multiple Data Sources Barnard s loop (in H-alpha, almost human-visible) surrounding Orion. 20

21 Aligning Multiple Data Sources H-alpha merges with David Malin optical image of Horsehead nebula: the three belt stars fill upper right of screen. 21

22 Aligning Multiple Data Sources Horsehead nebula (visible wavelengths, but very faint) is anchored to the left-hand star of Orion s belt, and covers half the length of the belt. 22

23 Modeling Astronomical Objects Spectral Data and Loops Supernova shells: Evidence and Modeling Multispectral data: Structures invisible to the naked eye appear in wavelengths ranging from microwaves (centimeters) to (10 X-ray m). ;10 LOOP I: Largest object in the Sky: From the multispectral data, we can detect previously unsuspected enormous structures from recent supernova explosions (probably a composite of three explosions, to be precise). 23

24 Multispectral Data Sources Axel Mellinger s Milky Way image in visible light. 24

25 Multispectral Data Sources Mellinger s Milky Way image in context of all wavelengths. 25

26 Multispectral Data Sources Hydrogen alpha at 6535 Angstroms. Orion to the right, Cygnus to the left. 26

27 Multispectral Data Sources The 21cm Hydrogen hyperfine data gives not only a hint of Loop I, but also has detailed velocity information. 27

28 Multispectral Data Sources Rosat X-ray data clearly show the Loop I arc, covering 25% of the sky visible from Earth! 28

29 Loop I: Supernova remnant model 3D model of Loop I viewed from 100pc away; dark regions are gas clouds visible as black obstructions in Milky Way Center. Yellow surface is Local Bubble, a huge void in our local interstellar material, modeled with Distance Editing Tool. 29

30 Loop I: Supernova remnant model Alternative 3D model of Loop I looking towards the corner containing the Sun and Earth. 30

31 The Heliosphere The Sun blasts out the Solar Wind, and plows through the corner of Loop I, leaving a trail behind it. Orion shows through at lower right. 31

32 Modeling Astronomical Objects The Largest Scale: Galaxies Galaxy Data Catalogs: One of cleanest Galaxy Data Sets: Brent Tully, University of Hawaii. Milky Way: obstructed view due to dust and other material; we have to guess what it looks like; usually use image of our twin Andromeda galaxy, or statistical models containing major seeable features. Close Neighbors: Sagittarius dwarf, nearby, obscured by Milky Way; Large and Small Magellanic clouds visible in Southern Hemisphere. Globular clusters: 1000 small, round clusters of stars floating around Milky Way. Local Group: Forty or so galaxies, a few like the Milky Way and Andromeda, the rest smaller satellites. 32

33 Galaxy Viewer: Milky Way and Local Group A simulated image of the Milky Way (we can t see it), and the local group, with Small and Large Magellanic Clouds. 33

34 Galaxy Viewer: Milky Way and Local Group Annotation capabilities of Galaxy Viewer. Earth is at Center of axes, Large Magellanic Cloud is selected. 34

35 ANIMATION: Solar Journey 35

36 ViewingtheBigPicture of the Cosmos LIGHT is all we measure. Speed of light is finite. So every OBJECT we see is a TIME STAMP. That is, the light took a certain, finite time to reach the earth. NEARBY OBJECTS: have young light. DISTANT OBJECTS: have old light. 36

37 The Task: Viewing the Cosmos View Frustum through the Universe 37

38 Viewing the Cosmos The Universe presents MANY scales: 38

39 ...thecosmosatearthscale 39

40 ...thecosmosatthedawnoftime 40

41 Scales of the Cosmos Typical Scales: 1 au = 1: m Earth-to-Sun ly m Alpha Cent. A/B = 4.35 ly (A and B are only apart) 1 = au 23 pc 3:26 = m 16 ly = dist. where subtends 1 arcsec au 1 One AU 1/3600 degree (1 arcsec) One AU One Parsec 41

42 Cosmic Scales, contd... Object (Meters) Power of 10 Planck length -35 proton -14 hydrogen atom -10 virus -7 cell -5 human 0 Earth 7 Solar system 14 Milky Way 21 Local galaxies 23 Super-clusters 25 Known Universe 27 42

43 History of Cosmic Scale Viz 1957: Boeke. Jumps 40 page book: The Universe in Forty 1968: Eames draft. Rough draft of Powers of 10 movie. 1977: Eames final. Powers of 10 movie, converging squares. 1982: Morrison book. Book annotating the movie. 1996: IMAX movie. Cosmic Voyage with Morgan Freeman, converging circles

44 How to Display Many Scales at Once To build Interactive System, choose a rendering method based on window error and distance: Full 3D if image motion > a pixel or so 2D Environment Map if you can t see a motion. Hierarchies of representations to let the scale determine the semantics; extended objects need special multiplelayer geometry also. 44

45 Scaled Navigation Wayfinding in highly scaled environments must also be scaled. Use Constrained Navigation to fix a scale-sensitive sidewalk. At each scale, adjust navigation response roughly to match the screen scale. 45

46 Images from three viewpoints on the log-scaled wedge path from 46 the Earth to the Moon.

47 Images from three viewpoints on the adaptive constraint manifold 47 with Earth, Solar System, and Milky Way.

48 Visualizing the True Light Cone of Visibility Distance scales also reflect time due to the finite speed of light. Construct a new light cone by warping the Universe. This symbolic cone shows the space-time structure of observable astronomy. 48

49 Whole Universe ;! Symbolic Light Cone... 49

50 Whole Universe ;! Symbolic Light Cone... 50

51 Whole Universe ;! Symbolic Light Cone... 51

52 Whole Universe in Time-Stamped Light Cone 52

53 ANIMATION: Cosmic Clock 53

54 CONCLUDING REMARKS The Challenges of Virtual Astronomy: Astrophysical data sources do not lead easily to usable computer graphics models. Need TOOLS. Integrating multiple data sources is nontrivial. Viewing and Navigating across enormous scale ranges is a unique problem. 54

55 ACKNOWLEDGMENTS Support: Supported in part by NASA grant NAG Other Major Contributors: Philip Chi-Wing Fu (Indiana University) and Eric Wernert (Indiana University Advanced Visualization Laboratory). Major Sources of Data and Models: NASA STSci, NASA Goddard, Hipparcos group, Hubble Space Telescope, ROSAT Mission; Timur Linde, Sean Carroll, Douglas Finkbeiner, Brent Tully, Axel Mellinger, David Malin, and many others. 55

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