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Great Sky Surveys to z=0.2 (2.4Glyr) Quaser Surveys to z<3.0 (11.47Glyr) Hubble Deep Fields to z=5.5 (12.6Glyr) Gamma Ray Bursts to z=6.3 (12.86Glyr) Cosmic Microwave Radiation Background at z=17.5 (13.4Glyr)
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May 2007- Jan. 2008: Due to enhanced security in Microsoft Internet Explorer 7.0, the 3D Cortona ActiveX plug-in will not activate all features implemented by the 3D renderings provided here. Security settings in Internet Explorer 7.0 will need to modified to fully use the Cortona Active X control. Normally, the Cortona viewer runs fine under MS IE7.0. However, the original version of this site was written under MS IE5.0 and an earlier version of Cortona Viewer. Subsequent MS IE7.0 security modifications blocked some of the earlier functions relied upon in these 3D VRML renderings, unless they are explicited allowed by the user under MS IE7.0. The ParallelGraphics Cortona viewer is a widely distributed, major commercial VRML 3D plug-in and, in this author's experience, can be implicitly trusted. trusted. Always are always use the links marked "Self-loading Cortona VRML".
Modifications to MS IE7.0 Internet Security Settings to allow the Cortona Viewer to fully implement the 3D renderings: Under MS IE7.0, under Tools | Internet Options | Settings | Security | Internet | Custom Level, set:
The major VRML 3D rendering feature implemented is these modifications is object identification rollover. When the cursor rolls over a object shown in the 3D renderings, its NGC catalogue or other id name, its galatic latitude and longitude, and its distance in kiloparsecs, is shown on the status bar.
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Alternatively, you can right-click here, to download a local copy mirror of this site and then run the VRML worlds from your local harddrive. Direct VRML links are included on the assumption that future versions of MS-Internet Explorer and Cortona will resolve the incompability.
A V magnitude of "99" means that no reliable magnitude catalogue entry could be found, or, in the case of dark clouds, that an emissive magnitude is not applicable.
The catalogue can be exported to a Microsoft Excel spreadsheet by opening the top table labeled "J2000 coordinates." Copy the internet url of the table from your browser's address bar. Use the File Open dialogue in MS-Excel and paste the url into the file name box. Excel will open and convert the internet table into a form that you can sort and filter within Excel.
Spending as much time as possible at the eyepiece makes for a good amateur astronomer. It is in this spirit that the above cross-reference catalogues were generated, i.e. - to reduce object look-up times. It is in this spirit, the following supplemental planetarium catalogue files for the freeware Cartes du Ciel planetarium software are offered. The author's intention is that the planetarium program catalogue will provide a comprehensive but narrowed list of deep sky objects accessible by the amateur, such that on any one night, a reasonable set of celestial objects of each type will always be visible. The 3D renderings provided below are intended to supplement but not supplant enjoyment of the night sky.
Right-click and "Save Target as" -
The user can locate objects of the same type or in the same structural association (e.g. the Perseus Arm) using the lookup lists, locate the object in their telescope assisted by the Cartes du Ciel planetarium software or other package, and then supplement that enjoyment with the 2D and provided below. The structural assignments and 2D and 3D renderings provide sufficient information to prepare observing tours by location, e.g. - "Open Clusters of the Perseus Arm."
Distances to celestial objects outside the solar system are inherently uncertain. Perhaps other than a stars within 100 parsecs of the Sun whose triaxial position was determined by the European Space Agency Hipparcos satellite, most astronomical positions are known with certainty to a tolerance between 5%-30% of their actual positions. The level of certainty depends on the method used to fix their position. While astronomical journals and catalogues were searched in order to assign a supportable distance to the objects in the consolidated catalogue, the reader should view such distances as general low-precision estimates. Read more about astronomical distances at Ned Wright's Cosmology Tutorial . . . (external content).
The vast distances at which astronomical objects are found is intimately linked with time by the limitation of the speed of light.
As examples, take Betelgeuse (alpha Orion) at an approximate distance of 465 light-years; Sirius (alpha Canis Major) at an approximately distance of 8.5 light-years, and NGC884, an open cluster that is part of the Perseus Double Cluster, at a distance of 7,600 light-years. When we see these stars and cluster at night, their light is reaching us from different time frames.
When we look up at night, we see stars whose light tells us of events are arriving from millions of different time frames. Think of it in terms of an analogy to lightning bolts on the Earth. When sitting inside during a lightning storm, one sees the flash of the bolt against window curtains and then a few seconds later hears thunder arriving. The further the lightning bolt, the longer it takes for the sound of the lightning to reach us. Even when sitting indoors, it is possible to build a mental map of the distance to the lightning bolts just from amount of time it takes for the sound of the bolt to reach us. The same holds true for the stars, except that the "lightning bolt" from the star can take years, thousands-of-years or even millions-of-years to reach us.
This experience is counter-intutitive to our daily life. We are used to seeing light arrive in a few billionths of a second from nearby objects - like a car across the street or the person sitting next to you. Everything in daily life is in the same time frame.
When the positions of astronomical objects are expressed based on the light currently arriving from different timeframes of when the light left those objects, such positions and object distances are expressed as distance-then. This is common form of astronomical position and distance seen in star categories.
For many nearby objects within the Milky Way, like Betelgeuse, Sirius, or NGC884, their position and distance can also be expressed as distance-now. Distance-now is the projected position and distance of an object in our present time frame on Earth. Take open cluster NGC884. In general, we know what direction it is traveling in the night sky and how fast is moves per year. By projecting where it will be in 7,600 years, its position can also be expressed as "distance-now" or where it is at the current time.
Many objects in the night sky, like very distant galaxies, have a known distance-now but there is no way to determine their present triaxial positions. We know their distance-then positions, based on the sometimes billions of years that it has taken for their light to reach us. We may also know generally whether they are moving towards or away from us. But such objects move so slowly that we do not know in which specific direction, in terms of the points on the compass, that these far galaxies are moving. Because of this lack of knowledge, modern astronomy cannot define a triaxial position in the "distance-now" timeframe for many galaxies.
Because the distance-now three dimensional positions for many far galaxies is unknown, the distances stated in the 2D figures and 3D renderings that follow are always distance-then positions - its position when the light left the source object - as normally occurs in all charts and catalogues used by astronomy hobbyists.
But readers should be aware that they are seeing only a snapshot of the universe as it appeared particular times in the past. Everything in the night sky has moved since the light that we now see has reached us.
The Powers of Ten analogy, first pioneered in the 1950s by Kees Boeke and in the 1960s by Office of Charles & Ray Eames, provides a coherent framework for presenting the relative size of the universe. Gott (2005). In the Powers of Ten analogy, the universe is presented in units of one-centimeter times the number 10 raised to the nth power. The solar system is in the range of 10 to the 15th power, the Milky Way Galaxy is in the range of 10 to the 21th power; and the Virgo supercluster in the range of 10 to the 24th power. The baseline unit to present the following 2D and 3D renderings is 1,000 parsecs, or the kiloparsec. One parsec is the physical distance represented by a star that subtends 1 arcsecond of angular distance when photographed by two observers separated by 1 astronomical unit - or the distance between the Earth and Sun. This angular distance, or parallax, is usually measured by taking two photographs of a star separated by six months in time. One parsec is equal to approximately 3.26 light-years; one kiloparsec 3,260 parsecs. Where appropriate, in addition to the kiloparsec radius of 2D or 3D rendering, the corresponding size of a 2D or 3D rendering in the Powers of Ten analogy is also stated.
The Parallelgraphics Cortona VRML player is a freeware Microsoft Internet Explorer, Netscape Navigator and Mozilla internet browser plug-in. It enables a full-featured implementation of the VRML 2.0 specification. The 3-D plots rendered below will not run under the native Microsoft VRML plug-in or under the Blaxun VRML plug-in.
For some 3D renderings, Microsoft Internet Explorer compatible on-the-fly loading web pages are provided that temporarily loads and runs the Cortona VRML player. Use the links marked "Self-loading Cortona VRML," below.
A key tip for using the 3D renderings for views within 8 kiloparsecs of Sol: The 3D renderings are normally centered near the Milky Way galactic core. An alternative to using the preprogrammed viewpoints near Sol is to use the Control Panel, to turn the "Galactic Arms" schematic to "off." This will recenter the 3D world near Sol and allow the objects within 2 kiloparsec of Sol to be examined using the normal Study and Turn modes. To cycle through the preprogrammed viewpoints, simply press the {Page Down} key.
A beginning point for understanding the Milky Way Galaxy is to understand what parts of the galaxy are seen throughout the year as the Earth completes one orbit of Sol. This understanding requires gaining an appreciation of the tilt of the Earth's orbit (the plane of the ecliptic of the Solar System) with respect to the galactic plane at the equinoxes and the solstices. The tilt of the ecliptic plane with respect to the galactic plane is extreme - about 62 1/2 degrees.
A result of the high inclination of the Earth's orbital plane to the galactic plane is the Earth's view varies widely throughout the year. At the vernal or spring equinox, the Earth is at its highest northern point relative to the galatic plane. The Milky Way's galactic plane is nearly coincident with the observer's horizon. Figure 9. An observer at 40 degrees North latitude looks "up" and "out" the top of the Milky Way's plane through the relatively star-free region of the Coma Bernices. Three months later at the summer solstice, the Earth has moved counterclockwise one-quarter of its orbit and the observer at 40 degrees North latitude looks "sideways" towards the Milky Way's galactic core and the rich star and gas regions of the Sagittarius Arm and the constellation Sagittarius, e.g. - the Lagoon Nebula, Messier 8. At midnight on the summer solstice, the plane of the Milky Way appears to run north and south relative to the observer's horizon. Figure 10. At the autumnal equinox, the 40 North latitude observer now looks "down" and "out" the Milky Way's plane towards the south galactic pole. Figure 11. At midnight on the winter solstice, the observer is again looking "sideways," through rich star fields and gas nebula in the galactic plane to the next galactic arm out - the Perseus Arm. The Orion Nebula, M42, is located in this direction, as is the "unwinding" anti-spinward direction of our local Orion Arm. Figure 12.
The following are 360 degree altitude-azimuth charts of the night sky at 12 midnight and 9pm at the equinoxes and the solstices, generated using Cartes du Ciel:
The orientation of the Earth in its orbit relative to the galactic plane is best understood by taking mental snapshots of the night sky at midnight at the equinoxes and the solstices. However, most amateurs are used to seeing the night sky at 9pm local time. The Earth's daily rotation also effects the apparent orientation of the Milky Way to the observer. In the foregoing figures, the night sky as seen at midnight and 9pm local time are illustrated. Comparing Figures 9-12 and 13-16, there is an evident pattern. The sky at midnight at the spring equinox (Figure 9) looks nearly identical to the sky at 9pm on the summer solstice (Figure 14). Similar pairings are seen for the other equinoxes and solstices. Figures 10 and 15, 11 and 16, 12 and 13.
Even with these 2D representations, visualizing the Earth's orbit - the ecliptic - with respect to the Milky Way's galactic plane can be difficult. The following 3D renderings provide a supplemental visual aid. In the 3D renderings (see Figure 17), the orbit of the Earth is greatly exaggerated in size. If drawn to scale, the entire solar system would be a minisule point at the intersection of the axes. The Earth is shown at the equinoxes and solstices.
Two sticks pierce each Earth. The black stick shows the orientation of the Earth's axis and runs through the Earth's North and South poles. The second red stick piercing each Earth shows the geographic location of an observer at 40 degrees North latitude in North America. The Earth is rotated to its relative position at midnight. The direction of the tilt of the Earth's axis is fixed and remains the same regardless of its orbital position as the Earth revolves around the Sun in a counterclockwise direction. This results in some visual anomalies. On the day of the vernal or spring equinox at midnight, the Earth is tilted away from the direction of the Earth's travel in its orbit. On the day of the summer solstice at midnight, the Earth is tilted perpendicular to direction of orbit but pointed towards the Sun. On the autumnal equinox at midnight, the Earth is tilted towards the direction of orbital travel; and, at the winter solstice, perpendicular to its orbital travel, but away from the Sun.
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In the 3D renderings, next to each Earth globe are floating panels that show the corresponding view of the night sky at 12AM and 9PM local time. These panels are the same as Figures 9-16, above. The user can rotate the 3D renderings in order to build a better map of the relationship of the Earth's orbit to the Milky Way's plane and structure.
A bright green line that extends from the origin of the axes in the 3D renderings represents the solar apex, or the apparent direction that the Solar System is moving. The solar apex is in the constellation Hercules (J175700.07+262829.5, G052.00+23.00 per Jaschek 1992). The solar apex was discovered by finding the average proper motion of all stars in various directions. Walkey 1946. Higher proper motions, on average, of nearby stars occur near the solar apex as illustrated in Figure 18. This indicates that this is direction that the Solar System is moving. The solar apex in the constellation Hercules appears in Figure 10, Summer Solstice at 12AM, and in Figure 15, Autumnal Equinox at 9PM, above, and in the corresponding floating panels in the 3D renderings. Another consequence of the Earth's orbit relative to the galactic plane is that amateurs see a limited part of the Milky Way during each major season. These effects can be seen in Figures 9-16 above and the foregoing 3D renderings. |
 Figure 17 - Ecliptic Plane and Galactic Plane illustrated - 3D VRML Snapshot  Figure 18 - Proper motion of nearby stars during the last 10,000 years and the solar apex - from Cartes du Ciel |
In the spring at midnight, amateurs can look "up" and "out" the "top" of the Milky Way's plane and have a relatively unimpeded view of distant galaxies. Figure 9. At the summer solstice at midnight, rich star fields that are dense with gas clouds and open clusters in the galatic plane towards the galactic core (galactic longitude 0 degrees) are visible. The "spinward" portion of our local Orion-Cygnus galactic arm is visible through 90 degrees galactic longitude. Figure 10. At the autumnal equinox, the amateur can see portions of the Perseus Arm stretching east to west along the local zenith from Cygnus (90 degrees galactic longitude) to Gemini (~180 degrees galactic longitude). Figure 11. But the observer can also see "down" and "out" the Milky Way's plane towards the south galactic pole - into a relatively star free region and towards distant galaxies in the constellation Fornax. Figure 11. At the winter solstice, the amateur again sees the rich star fields full of open clusters and nebula, like M42 in Orion, all contained in the Milky Way's galactic plane. Figure 12. Near the winter solstice, the northern observer sees from the galactic anti-center near Gemini towards galactic longitude 270 degrees in the constellation Vela. This portion of the sky, near Canis Major, also contains the "unwinding" or "antispinward" portion of our local Orion Cygnus Arm.
Close readers of the Earth and Ecliptic Plane 3D renderings may notice a facial contradiction. The ends of the right ascension axes are labelled with name of the corresponding event, e.g. - autumnal equinox, winter solstice, etc. The corresponding Earth globe and night sky panels are labelled with the right ascension event 180 degrees opposite to each Earth globe. For example, the axis labelled "RA 12 hr . . . Autumnal Equinox" is next to the Earth globe and panels marked "Vernal/Spring Equinox." This is not an error. When the Earth is at the vernal equinox, the Sun appears 180 degrees away against the background of the constellation Aries at right ascension 0 hours. The display is confusing, but accurately reflects the physical model.
The following 3D renderings include selected stars with Bayer or Flamsteed identifications in the author's personal observing catalogue of approximately 3,000 objects. These stellar objects are not included in the Consolidated Catalogue of 823 deep sky objects. These renderings are not intended to include all Bayer stars in constellations with 3D triaxial positions or to pair those triaxial positions with the constellation stick figures seen in 2D on the celestial sphere. The intent of these renderings is to illustrate that what we perceive as the constellations primarily are a halo of nearby stars within 150 parsecs, within the Local Bubble, or within Gould's Belt, along with a smattering of bright A, O and M giant stars beyond 200 parsecs. This is the "mid-range sky" between what amateurs call the "shallow sky" of the solar system and the "deep sky" containing deep sky objects.
Figure 19 - Halo of stars around Sol within 150 parsecs - 3D screenshot |
Figure 20 - Example Her and Per Constellations - 3D screenshot |
Stars from this sample and a few individual constellations are rendered as follows. These renderings contain a sample, but not all of the stars, in a constellation's stick figure.
Rolling over objects while in the 3D renderings displays object information in the status bar:
The some of the nearby stars shown in the foregoing renderings can be organized by absolute magnitude and color index into a Hertzsprung-Russell diagram:
Rolling over objects while in the 3D renderings displays object information in the status bar.
 Figure 22 - 2D Orion Arm x-y plane 32kpc view |
 Figure 23 - 2D Orion Arm z-x plane 32kpc view |
Structures illustrated in this rendering include:
 Figure 24 - 2D Outer Arm x-y plane 32kpc view |
 Figure 25 - 2D Outer Arm z-x plane 32kpc view |
 Figure 26 - 2D Perseus Arm x-y plane 32kpc view |
 Figure 27 - 2D Perseus Arm z-x plane 32kpc view |
 Figure 28 - 2D Sgr-Carina Arm x-y plane 32kpc view |
 Figure 29 - 2D Sgr-Carina Arm z-x plane 32kpc view |
Three Scutum-Crux Arm objects contained in the Consolidated Catalogue and that are shown in the above 3D rendering are not included in the 2D renderings of Figures 26 and 27.
Figure 30 - Age Distribution of Open Clusters and Clusters of Stars in the Consolidated Catalogue
The galactic year, the time it takes the Sun to complete one revolution around the Milky Way's core, is approx. 220 million years or 8.34 log10(years). Half of all open clusters disperse in just under one galactic year (8.13 log10(years) or 218 million years). The third quartile of open clusters disperses in just under two galactic years (8.6 log10(years) or about 430 million years).
Popular old clusters and moving groups that have survived more than two galactic years and into the fourth quartile include M044 (Beehive Cluster), M048, M067, M073, M093, the Hyades Moving Group, and the Coma Berenices Star Cluster.
The youngest clusters in the consolidated catalogue are aged around 6.7 log10(years) or approx. 5 million years old. The youngest three are the Tau CMa Cluster a.k.a. the Northern Jewel Box (NGC2362, Caldwell 64); NGC1980 surrounding iot Orion in the Orion stellar nursery region; and, NGC2239, a star cluster associated with the Rosetta Nebula stellar nursery in Mon.
| Mag/Size | 1-9 | 10-14 | 15-24 | 25-54 | 55-94 | >95 | Unknwn | Total | |
|---|---|---|---|---|---|---|---|---|---|
| 2-5 | 4 | 6 | 11 | 13 | 5 | 39 | |||
| 6-7 | 26 | 14 | 26 | 9 | 1 | 76 | |||
| 8-9 | 28 | 7 | 7 | 1 | 1 | 44 | |||
| 10-11 | 8 | 1 | 9 | ||||||
| 12> | 1 | 1 | 2 | ||||||
| Unkwn | 5 | 2 | 3 | 3 | 1 | 1 | 15 | ||
| Total | 72 | 29 | 47 | 26 | 8 | 1 | 2 | 185 |
Notes: Excluding one cluster in the Tarantula Nebula for a total of 186
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Clusters and moving groups share a common proper motion, as illustrated by the following figure generated with the Cartes du Ciel planetarium software. The figure shows the proper motion and direction of stars in the M45 - the Pleiades Moving Group - over 5,000 years. The difference between non-members and the co-moving cluster members is evident.
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 Figure 30 - Proper motion of M45, the Pleiades Moving Group |
Planetary nebula ages have been measured to 40 million years. Xilouris (1996). Planetary nebulas begin with their characteristic end-view circular shape seen in M57 (M57 at SEDS), M27 (M27 at SEDS) or the Helix Nebula (NGC 7293 at SEDS). As time progresses, interstellar wind or the effects of nearby bright stars degrades this shape and they dissipate into the interstellar medium. See Xilouris (1996).
While planetary nebula may be spherical in their early stages of mass loss, they may not remain so. In later stages, they can become elongated symmetrical tubes, as illustrated by a Hubble Space Telescope picture of the PN MyCn18. Space Sci. Instit. 1996. Planetary Nebula McCn18: An Hourglass Pattern Around a Dying Star. Photo STScI-PRC1996-07. This nebula has a strikingly similar appearance to M57 and the Helix nebula, but is viewed from a side angle instead of "end-on."
| Mag/Size | <2 | 2-10 | 12-60 | 60> | Total |
|---|---|---|---|---|---|
| <10 | 7 | 1 | 1 | 9 | |
| 10-11 | 9 | 2 | 1 | 12 | |
| 12-13 | 5 | 1 | 1 | 7 | |
| 14-15 | 5 | 3 | 2 | 10 | |
| 16> | 1 | 1 | 2 | 4 | |
| Unknwn | 5 | 5 | |||
| Total | 32 | 5 | 8 | 2 | 47 |
The above rendering only includes bright and dark nebula objects that are in the consolidated catalogue. Dark nebulas are under-represented. Another rendering presented above - "Nebula and OB Association Tracers of the Orion Arm - 32kpc view (galactic coordinate system)" - includes all Barnard Catalogue dark nebula with a known distance, including those not in the consolidated catalogue. That rendering, which contains more nebula, better illustrates the association between molecular clouds and Milky Way galactic arm structure.
The structural components of the Milky Arms's can be seen in astrophotographs taken at various wavelengths of light. NASA's Astrophysics Data Facility maintains a compilation of All-Sky Milky Way photos at its Multiwavelength Milky Way Science Users site. Read more at this site's Multi-Wavelength Image Reference page...
This 3D rendering contains 80 globular clusters in consolidated catalogue (omitting one distant cluster) out of approximately 120 known globulars.
Compare Figure 1 in Shapley's 1919 "Twelfth Paper: Remarks on the Arrangement of the Sidereal Universe." Mt. Wilson Obs. Contrib. No. 157:209-234; compare Figures 3 and 4 in Shapley's Fourteenth Paper (external content); compare Zinn, R. 1985. Figure 3 - [Metal Rich and Metal Poor Globular Clusters]. In "The globular cluster system of the galaxy. IV - The halo and disk subsystems." 1985ApJ...293..424Z (external content)
Figure 31 - Metallicity Distribution of Globular Clusters in the Consolidated Catalogue
There are two populations of globular clusters divided by metallicity. Zinn (1985). The smaller population has high metallicity, is redder in color, is within 7 kpc of the galactic core and is flattened in shape. The larger second population has lower metallicity, is bluer in color, generally is beyond 7 kpc of the galactic core and is spheroid in distribution. Both populations were formed across a span of 13 to 9 billion years ago, with some bias towards the high metal population being formed more recently. Chaboyer (1996). How the two populations of nearly equal-aged globulars formed in the Milky Way with differing metallic contents still remains under investigation. There are competing hypotheses. Pulliam (Mar. 2006, S&T); Brook (2003) (hierarchial consolidation); Martin (2004) (Canis Major Dwarf galaxy accretion); Forbes (2004) (not Canis Major Dwarf galaxy accretion).
| Mag/Size | <5 | 5-10 | >11 | Total |
|---|---|---|---|---|
| <7 | 5 | 8 | 13 | |
| 7-8 | 7 | 19 | 3 | 29 |
| 9-10 | 30 | 5 | 1 | 36 |
| 11> | 4 | 4 | ||
| None | 3 | 1 | 4 | |
| Total | 44 | 30 | 12 | 86 |
 Figure 32 - 2D Milky Way - Entire catalogue - x-y plane 16kpc view |
 Figure 33 - 2D Milky Way - Entire catalogue - z-x plane 16kpc view |
The Milky Way is surrounded by a halo of dark matter that can be partially traced in HI gas at that gas's half-height density. The Milky Way's rotation warps the distribution of this gas. In this rendering, the HI galactic warp of the Milky Way is modeled using the half-height of the HI gas (non-optical) gas disk as an indicator, Henderson (1982)'s measurements of HI gas between the solar circle and 17 kpc, and Binney (1998)'s fitted-curve-plot between 16 kpc and 30 kpc. (Binney 1998 at p. 566). The full-height distribution is more complex than modeled here.
Professional astronomers have mapped similar traces of the HI gas warps around other galaxies. Some are well-known to and are visible to amateurs. Hibbard (2003); Christodoulou 1993; Sancisi 1976; Rogstad 1974.
The Milky Way System includes the Milky Way and nearby objects that are gravitationally bound to it. Such objects include the Large and Small Magellanic Clouds, and the Sculptor, Fornax, Canis Major and Sagittarius Dwarf galaxies. This rendering includes 5 globular clusters whose distance from the galactic core is greater than 30 kpc and which could not be included in the globular cluster/galactic halo rendering, above.
Some large-scale structures are omitted from the above schematics due to a lack of information on their tri-axial positions, their confusing graphical display, or lack of resources. Omitted objects include:
Rolling over objects while in the 3D renderings displays object information in the status bar.
Normally, large scale renderings of the galaxies are done in de Vaucouleurs (1975) supergalactic coordinate system. The supergalactic coordinate system is approximately rotated 90 degrees from the galactic coordinate system:
| Designation | Cons | J2000 Coords | Galactic coords |
|---|---|---|---|
| Supergalactic North Pole | Her | J185501.01+154232.2 | G047.37+06.32 |
| North Galactic Pole | Com | J125126.28+270741.7 | G000.00+90.00 |
In the 10Mpc and 40Mpc 3D and 2D galaxy renderings, the galactic coordinate system is used throughout - mostly as a programming convenience. The supergalactic coordinate system can emulated by simply turning the galactic system on its side, as shown in Figure 4, above.
The Local Group consists of the Milky Way System and the components of the Andromeda Galaxy System. These two local galaxy systems are graviationally bound to each other around a common barycenter.
The 3D rendering of the Local Group is sparse, due to the low-number and widely separation of objects. The view begins near the Milky Way Galaxy and some of the members of the Milky Way System. Use the Fit option to expand the screen to include the Andromeda Galaxy. Other excellent figures showing the members of the Local Group are Figure 8.1 in Waller's 2003 book - Galaxies and the Cosmic Frontier (2003gcf..book.....W) and Powell's Atlas of the Universe website.
| Color | Tully galaxy group |
|---|---|
| Dark Blue | Local Group |
| Red | Coma - Sculptor Cloud |
| Green | Leo Spur |
| Purple | Triangulum Spur |
| Teal | Virgo Cluster and Southern Extension |
| Yellow | Fornax Cluster and Eridanus Cloud | Dorado Cloud |
| Black | Other or none |
Beginning in the range of 20Mpc (65.2Mlyr; 6.171 x 10^25 cm) to 40Mpc (130Mlyr; 1.234 x 10^26 cm) from the Milky Way, relativistic effects begin to alter the measurement of galaxy distances based on redshifts. One method of measuring the vast distances to galaxies is by Hubble constant and the redshift of the galaxy. Hubble (1929). The simple co-moving distance form of the Hubble relationship is expressed as:
For example, a galaxy receding from the Milky Way at 15,000 kms has a z of 0.03 or about 15,000 kms / 300,000 kms. The corresponding Hubble distance is 15,000 kms / 71 kms per Mpc or about 211 Mega-parsecs.
Beyond 20 Mpc, computing Hubble distance from a redshift "z" or a recessional velocity is not a simple matter. The basic simple Hubble equation of D_Mpc = v / H_0 is adjusted for relativistic effects and on assumptions about the shape of the fabric of space. Such matters are beyond the scope of this presentation. Suffice it that readers should understand that at the vast distances that galaxies are from the Sun, distance can be expressed a number of ways - in terms of mega-parsecs (Mpc), in terms of redshift or "Z", or in terms of the light-years of travel time. Read more on these cosmology questions at Ned Wright's Cosmology Tutorial and Ned Wright's Hubble Distance Calculator...
The practical effect of these relativistic and space-shape effects for the hobbyist is that that raw Hubble distance - D_Mpc = v / H_0 - or Hubble distance-now can yield confusing values greater than the generally accepted age of the universe of 13.7 billion years. For example, a distant quasar with a "z" value of 5.5 using the Hubble distance-now equation implies that it travelling at faster than the speed of light at 1,560,000 kilometers per second. The distance-now - or its co-moving distance - for the quasar is approximately 23 Bpc and 75 billion-light years. Such distance-now values are not consistent with age of the universe of 13.7 B light-years or Einstein's limit for the speed of light. The apparent inconsistency can be explained. First, although the speed of light that reaches us from a distant quasar is limited, there is no limitation on how fast the fabric of space expands. It is believed that in early stages of the Big Bang expansion, the fabric of the universe inflated at superluminal speeds. Davis 2004; Davis 2001. Second, the expansion of the universe is often explained using the analogy of a loaf of uncooked rasin bread dough rising in an oven. Although the entire loaf of bread expands uniformly, more distant parts near the "edge" of the loaf relatively appear to expand faster when viewed from other parts. This creates the appearance of superluminal speed. In the counterintutitive world of space-time cosmology, a hypothetical person at the distant galaxy sees the same thing when looking toward the Milky Way - we appear to be moving at superluminal speeds. Read more at Ned Wright's Cosmology Tutorial (external link)...
The counter-intuitive nature of Hubble distance-now - or the co-moving distance - is another reason why distances to far galaxies and quasars is usually presented using distance-then - which is always less-than and is consistent with the generally accepted age of the universe. Again, distance-then adjusts the travel time of the light reaching us from a far galaxy for relativity and for assumptions about the space of the fabric of the universe. See Ned Wright's Hubble Distance Calculator (external link).
Because of an inherent observational bias in collecting redshift "z" data - towards the observation point - it is possible members of a spherical cluster of galaxies with similar distances to be measured as being strung out in a line. This effect is a data artifact. This creates the visual appearance of a finger pointing towards Sol, and is jokingly named the "Finger of God effect" by some. When viewing diagrams of galaxy positions beyond 20 or 40Mpc, be aware that the actual positions of a string of objects may be more spherical in shape due to this effect. Conversely, the "soapbubble froth" of voids and superclusters of galaxies seen in the large scale structure of supergalactic space is real - even after the Finger of God effect is taken into account.
When one looks up into the northern night sky during the spring and sees the "Realm of the Galaxies" running from Virgo through Coma and up into UMa, those 2D celestial sphere locations correspond to galaxy clusters positioned in three dimensional space.
Combining distances in Tully and Fisher's 1988 Nearby Galaxy Catalogue and their 1987 Nearby Galaxy Atlas with extragalactic objects in the consolidated catalogue (N=423), a 3D picture of the local supergalactic structure can be constructed:
| Color | Tully galaxy group |
|---|---|
| Dark Blue | Local Group |
| Red | Coma - Sculptor Cloud |
| Green - dark | Leo Cloud |
| Green - light | Leo Spur |
| Purple | Triangulum Spur |
| Teal | Virgo Cluster and Southern Extension |
| Yellow - dark | Fornax Cluster and Eridanus Cloud |
| Yellow - light | Dorado Cloud |
| Black | Not coded in this view |
| Color | Tully galaxy group |
|---|---|
| Dark Blue | Color-coded in First Set |
| Red | Ursa Major Cloud |
| Red - light | Ursa Major Southern Spur |
| Green - dark | Canes Venatici - Camelopardalis Cloud |
| Green - light | Canes Venatici Spur |
| Purple | Cetus - Aries Cloud |
| Teal | Virgo-Libra Cloud |
| Yellow - dark | Pegasus Cloud |
| Yellow - light | Pegasus Spur and Perseus Cloud |
| Black | Not coded in this view |
|
The foregoing renderings also illustrate another feature of the supergalactic sky - voids: |
Figure 39 - Voids in the supergalactic structure - 3d screenshot |
| Mag/Size | <1 | 1 | 2 | 3 | 4 | 5-6 | 7-19 | 20> | Uknwn | Total |
|---|---|---|---|---|---|---|---|---|---|---|
| <8 | 2 | 3 | 5 | |||||||
| 8 | 3 | 1 | 3 | 4 | 3 | 14 | ||||
| 9 | 1 | 1 | 3 | 3 | 10 | 10 | 28 | |||
| 10 | 7 | 8 | 13 | 11 | 18 | 14 | 1 | 72 | ||
| 11 | 3 | 32 | 45 | 35 | 21 | 17 | 7 | 160 | ||
| 12 | 12 | 40 | 31 | 15 | 5 | 8 | 2 | 1 | 114 | |
| 13 | 7 | 10 | 8 | 4 | 4 | 1 | 34 | |||
| 14> | 1 | 2 | 1 | 1 | 5 | |||||
| Total | 23 | 91 | 100 | 71 | 41 | 57 | 40 | 8 | 1 | 432 |
|
|
The 40Mpc z=0.01 (130Mlyr; 1.234 x 10^26 cm) world of the consolidated catalogue and the Tully Nearby Galaxy Catalogue represents the practical limits of the amateur observer equipped with a consumer visual class telescope of up to 10" to 12" of aperture.
Beyond that is another world of extreme high z distances being investigated by professional astronomers. In the following renderings, the red two-polar 40 Mpc grid used in previous 40Mpc z=0.01 3D renderings is maintained at its 40Mpc size in order to give a sense of scale between the world of the amateur discussed above and the more distance realm's being investigated by the professionals.
A series of surveys have explored to the limit of the inherent brightness of typical galaxies as contrasted against the night sky's inherent brightness around visual magnitude 19. That distance roughly corresponds to z=0.2 or about 800 Mpc under current, generally accepted cosmological models, again for typical galaxies and Earth-based telescopes. (Other atypically bright objects, like quasars discussed below, have z values higher than 0.2, but are still visible to amateur and professional class Earth based telescopes.)
The following links can be used to view "wedge" slices plotting the positions of galaxies that are among the major results of each survey:
For the technically-minded, the size of the wedges were computed from the survey z value and a cosmological model of Omega-mass=0.27, Omega-energy=0.73 and H_0=0.71. The distance is the light-travel or distance-then time, converted to megaparsecs.
At the scale of these surveys (the 2dFGRS survey contains data on over 200,000 galaxies), galaxies no longer are referred to by group membership, as seen in the 40Mpc view, but are now aggregated hierarchically in clusters of galaxy groups called superclusters. Nomenclature for these groups and superclusters change between new surveys. Fairall (1990) and Tully's 1987 Nearby Galaxy Atlas provide a nomenclature schema for nearby rich or superclusters.
|
Abstract distance scalars like "z=0.2" or "203 megaparsecs" are difficult to relate to the concrete amateur experience of the 40Mpc Virgo supercluster sky. The following rendering shows the relative sizes of the Tully z=0.01 survey familiar to amateurs as compared to the first three survey wedges listed above:
At this scale, it becomes apparent at that DSO galaxy night sky familiar to amateurs inhabits a small portion of the bottom corner of the 2001 Zwicky Slice. |
 Figure 40 - Galaxy survey wedges to z=0.2 - 3D screen snapshot |
The best amateur rendering of this scale of supergalactic space remains Powell's Atlas of the Universe website and his view of supercluster space to 1.0 billion light-years, 306Mpc, or about z=0.075.
z=0.2 to z > 25 is equal to: (738.6Mpc; 2.4Glyr; v = 60000kms; 2.279 x 10^27 cm ) to (~4.1Gpc; 13.7 Glyrs; 1.265 x 10^28 cm ).
Being based above the atmosphere, the Hubble Space Telescope has the ability to reach magnitude depths beyond the Earth-based telescopes, but when it does so, the HST only can cover only a small area of the sky. Two famous Hubble photographs, the 1996 Hubble Deep Field and 2004 Hubble Ultra Deep Field, each cover approximately a 2-3 arcminute circle of sky, but the galaxies in the field are as far as z=5.5 distant. Bouwens (2004) (Hubble Ultra Deep Field); Williams (1996).
There are estimated to be approximately 170 billion bright galaxies and 6 x 10^22 stars in the observable universe. Gott (2005).
z = 3.0 is equal to: 3.52Gpc; 11.47Glyr; superluminal v = 900,000 kms; 1.086 x 10^28 cm.
Not all galaxies beyond z=0.2 are invisible to Earth based telescopes. Some - the quasars or quasi-stellar objects (QSOs) - have extremely bright cores. In 2003, the 2dFQSO Team completed a survey of over 20,000 quasars with z values to 2.5 (3.34Gpc; 10.9Glyr; 1.03 x 10^28) in the 2dGRS survey areas discussed above, resulting in the 2dFQSO wedge map. In 2005, the Sloan Digital Sky Survey released a new catalogue of over 40,000 potential QSOs in a small segment of northern sky. Schneider (2005).
A study of clumping in the 2dFQSO survey area found that quasars appear to be organized in soapbubble and froth type structures similar to that seen on a smaller scale with galaxies and galaxy superclusters. See Figure 5 in Miller (2004). In a newly reported study, Trujillo (2006), researchers suggest that the galaxies are not randomnly oriented around the "bubble" voids. Statistically, their axes seem to preferentially oriented pointing toward the center of the large voids.
Most quasars are too distant to be seen in amateur class telescopes. For example, there is one quasar in Clark's Appendix E catalogue - QSO 3C 273. In March 2006, amateur James McGaha published a list of 13 QSOs he had imaged with a 24" Newtonian. The five brightest with a magnitude of less than 16 are listed as follows:
| Id | Con | J2000 | V_mag | Dist. kpc | Notes |
|---|---|---|---|---|---|
| QSO J0407-1211 | Eri | J040748.43-121136.7 | 14.86 | 1687116 | Dist. 5.5B l/yr (z=0.57) |
| 3C273 | Vir | J122904.80+020307.2 | 12.86 | 601226 | Clark note: brightest quasar; dist. 1.96B l/y (z=0.158) |
| QSO J1436+6336 | Dra | J143645.80+633637.9 | 15 | 3190184 | Dist. 10.4 l/yr (z=2.07) |
| QSO J1634+7031 | UMi | J163428.99+703132.3 | 14.66 | 2730061 | Dist. 8.9B l/yr (z=1.33) |
| QSO B1946+768 | Dra | J194400.00+765400.0 | 15.85 | 3527607 | Dist. 11.5 l/yr (z=3.00) |
|
Again, abstract distance scalars like "z=2.07" or "3.5 megaparsecs" are difficult to relate to the concrete amateur experience of the 40Mpc Virgo supercluster sky. Similarly visualizing the positions of the Hubble Deep views and the 2dFQSO survey is difficult. The following rendering shows the relative sizes of the Tully z=0.01 survey size familiar to amateurs as compared to the positions and sizes of the objects discussed above in the "high-z quasarland":
|
Figure 43 - Five brightest quasars, major surveys and the original 40Mpc view |
Another source of light that contains information from the high-z universe is gamma ray bursts. At the January 2006 meeting of the American Astronomical Society, Dr. Bradley Schaefer presented a paper listing gamma ray bursts recorded by the Swift satellite with redshifts out to z=6.3. Schaefer (2006). See
Cosmic rays from extra-solar sources may be linked to severe lightning weather on the Earth. Some researchers have suggested that cosmic rays are the source of sprays of high energy electrons in the upper atmosphere. These electrons pierce through storm clouds that are positively charged on one side and negatively charged on the other. The cloud acts as an insulator. The high energy electron spray creates "tunnels" through the cloud and through which these charges can travel. The result is a cascading effect ending in a lighting bolt. See Beyond the high-z land of quasars finally lies the earliest light of the universe, evidenced in the cosmic microwave radiation background (CMRB) remnant, as mapped by the WMAP Team in 2003. In his logarithmic map of the universe, Gott (2005) places the WMAP CMRB image after the Big Bang at approximately z=17.5.
Technology has driven the great sky surveys forward since the first western (but lost) great sky survey of 850 stars was prepared by the ancient Greek Hipparchus in 125 B.C.E. See O'Conner 1997 (Hipparchus biography); Schaefer 2005 (hypothesized reconstruction of the Hipparchus catalogue in the Farnese Atlas statute). The invention of astrophotography and more accurate telescopes in the late 1800s launched the era of the photographic surveys with the Paris Observatory's Carte du Ciel survey. In the great sky surveys of the early 1900s, like the Henry Draper stellar catalogue of Milky Way stars, between 200,000 to 300,000 stars were catalogued by a group of 20-40 workers that examined thousands of photographic plates and typed-up index cards on each star. See The equivalent modern mass galaxy and star surveys were made possible in the 1980s by two new inventions. The first was the invention of the automated precision measuring (APM) machine by 2dFGRS Team. 2003. Picture of a Z-Machine (in Image Gallery). A z-machine sits in the optical path of a large telescope. A computer automatically detects galaxies in an image and positions light-gathering tubes - one of for each galaxy. With a z-machine, the redshifts or z's of approximately 400 galaxies can be measured per night. The second was the invention of the digital camera chip or "CCD" chip. The heart of the Sloan Digital Sky Survey is a telescope that uses banks of CCD chips and computers to image and catalogue down to the visual limit of Earth based telescopes. The 6dF Galaxy Survey in the southern hemisphere and the Sloan Digital Sky Survey in the northern hemisphere represent the future of deep space astrometry and photometry. Using these modern computer driven telescopes, the positions of hundred-of-millions of objects may be plotted. A future astrometry project that focuses on near-space is the joint European Space Agency (ESO) and NASA GAIA mission. The GAIA space telescope, scheduled to be launched in 2011, will photograph and determine accurate positions for 1 billion stars within a sphere of 20 kiloparsecs - or a significant portion of Milky Way Galaxy. GAIA will repeat the mission of the 1990's ESA Hipparcos satellite that determined accurate distances for approximately 120,000 stars out to approximately 100 parsecs, but on a much larger scale and using better, more sensitive, modern technology.The Cosmic Microwave Radiation Background as seen by WMAP (z=17.5; 13.4Glyr)
Figure 44 - WMAP Cosmic Microwave Radiation Background Image
Image provided by the NASA/WMAP Science Team
The Future of the Great Sky Surveys
Learn about history of astronomy, the structure of the Milky Way, how astronomers discovered the structure of the Milky Way, and the structure of the supergalactic universe by reading astronomical journal articles, websites and some hard copy books. Get a sense of how astronomical scientific knowledge is incrementally discovered through the scientific process. Although most of the journal articles contain higher level math that is beyond the average amateur, many journal articles contain narrative conclusions and figures that are within the range of most amateur readers. NASA ADS Services redistributes - for single download, personal reading - astronomical journal articles - many of which are subject to copyright protection. The Reader-Bibliography is an index to landmark journal articles and books and other resources with external content links to the NASA ADS and other websites. To learn more about Milky Way structure and astronomy history, start reading here . . .
Centre de Données astronomiques de Strasbourg - Simbad: This project has made use of the SIMBAD database, operated at CDS, Strasbourg, France.
Centre de Données astronomiques de Strasbourg - Catalogue Service: This project has made use of numerous catalogues redistributed through the CDS Astronomer's Catalogue Service, operated at CDS, Strasbourg, France. Catalogues that were utilized are listed in Bibliography and the Distance Bibliography. The use of those sources are by this reference is acknowledged and appreciated.
NASA Astrophysics Data System/Computation Facility at the Harvard-Smithsonian Center for Astrophysics - NASA ADS Abstract Services: This project has made use of NASA's Astrophysics Data System.
Parallelgraphics - Cortona VRML player: This project has made use of the Parallelgraphics free VRML Player (v. 4.2) in the development of its 3d renderings. << http://www.parallelgraphics.com/ >>
Nigel Henbest and Heather Couper: This project was inspired by the N. Henbest & H. Couper's 1994 book The Guide to the Galaxy. Cambridge Univ. Press. (1994gtg..book.....H).
Salt Lake Astronomical Society: At the time this site author was created, the author was a member of the Salt Lake Astronomical Society (SLAS). While SLAS neither participated in nor endorses this project, the use of SLAS's 16 inch Ealing Telescope at SLAS's Harmon's Observatory in the Stansbury Park Observatory Complex (SPOC) at Tooele, Utah remains a continuing inspiration, which is acknowledged here.
StatCounter.com: Provides site tracking data.
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It is the nature of the internet that information contained on it is temporary. This website was developed for the enjoyment of the amateur astronomical community and as an introductory educational aid for high school and college students. I encourage students and other amateurs to freely download, store and/or redistribute this website.
A local copy of this site on a laptop my also be useful for studying Milky Way structure and galaxy superstructure at the telescope's eyepiece in the field.
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Prepared by: K. Fisher 5/2006 fisherka@csolutions.net
