Introduction to Galaxies3D
The particular realm in space and time each of us have been given to live out our lives is one of the mysteries of our existence. As we describe the places that anchor the events of our lives, we may note:
We could also add:
We generally have a sense of where our home, our town, and our country lies in relation with neighboring homes, towns, and countries. Can we say the same for our star, our galaxy, our local group of galaxies, our supercluster? Who are our neighoring stars, galaxies, groups of galaxies, and superclusters? Where are they? Exactly in what "direction" so they lie?
Purpose of Galaxies3D
Galaxies3D is a website and software program to help you explore the above questions, to help you envision in three dimensions the location of and directions to prominent objects and structures in our universe. This website contains screen shot images and videos from the program, and a link to download the actual Galaxies3D program. The Galaxies3D program is free software and can be freely distributed.
Galaxies3D renders celestial objects and structures — stars, star clusters, nebulae, galaxies, galaxy groups and clusters, and superclusters — as identical-sized spheres attached via a line to a 10 x 10 grid. Because the size of the spheres and their identifying labels are uniform, nearer objects appear as larger spheres and labels, farther objects as smaller spheres and labels. The length of each line connecting each spheres to the grid corresponds to the distance of the object above the grid. The goal of this simple geometry is to evoke an intuitive feel for the three-dimensional structure of the scene before us:
The grids used are not random or arbitrary, but represent fundamental planes in the structure of our universe: the galactic plane, and the supragalactic plane.
The Galactic Plane
Our Milky Way galaxy is a barred spiral galaxy, consisting of:
The flattened disc of our galaxy containing the spiral arms defines a fundamental plane, the galactic plane:
For objects in our Milky Way galaxy, Galaxies3D anchors objects to a grid parallel to the galactic plane. The program tells you how far above or below the galactic plane the grid lies. One set of lines in the grid points towards the center of the galaxy lying in the constellation Sagittarius, some 26,000 light years away (more precisely, the lines labeled "To the Galactic Center" are lines parallel to the line in the galactic plane that points from earth towards the center of our galaxy). Distances are given in light years, or in "kilolight-years" (kly) = units of thousands of light years:
The Supergalactic Plane
Galaxies often congregate into groups, and larger groups called clusters. In turn, galaxy groups and galaxy clusters congregate to form "clusters" of galaxy groups and galaxy clusters, called superclusters.
In the 1950's, Gérald de Vaucouleurs noticed that nearby galaxies and galaxy groups appeared to congregate in a flattened, roughly disc-like structure, and first proposed they belonged to a "Local Supercluster" of galaxy groups and clusters, dominated by the large Virgo Cluster 52 million light years away. He defined a plane through this flattened, disk-like shape, the supergalactic plane:
For objects beyond our Milky Way galaxy, Galaxies3D anchors objects to a grid parallel to the supergalactic plane. The program tells you how far above or below the supergalactic plane the grid lies. One set of lines in the grid points towards the "core" of our Local Supercluster, towards the Virgo Cluster, some 52 million light years away (more precisely, the lines labeled "To the Virgo Cluster" are lines parallel to the line in the supergalactic plane that points from earth to the galaxy Messier 87, near the center of the Virgo Cluster). Distances are given in "Megalight-years" (Mly) = units of millions of light years, or in "Gigalight-years" (Gly) = units of billions of light years:
The Position of the Galactic Plane in the Supergalactic Plane
Galaxies3D will show you in three dimensions where objects — stars, star clusters, and nebulae — in our Milky Way galaxy lie in relation to the galactic plane. And Galaxies3D will show you in three dimensions where objects beyond our Milky Way galaxy — other galaxies, galaxy groups and clusters, and superclusters — lie in relation to the supergalactic plane.
But where does the galactic plane lie in relation to the supergalactc plane? How do we enlarge our vision of structures in the Milky Way to include a sense of where they lie relative to the plane of the Local Supercluster, the plane we call the supergalactic plane?
Here is an image from the Galaxies3D program showing the galactic disc as a circle of small spheres, one sphere for each 10 degree of galactic longitude, relative to the supergalactic plane. Our galaxy is sharply inclined into the supergalactic plane. You can see the "northern" face of our galaxy faces nearly straight on towards the Virgo cluster.
An observer standing on the supergalactic plane in the Virgo Cluster — the core of our Local Supercluster — would be blessed with the salutary perspective of seeing our Milky Way galaxy as a nearly face-on barred spiral galaxy. The Milky Way's central bar would be nearly horizontal, and — imagining a clock face over the Milky Way — the line extending from our Sun to the center of our Galaxy would lie at 1:30 o'clock: