[Photograph of the CGPS field in the Milky Way]

Location on the Sky

As stated in the Introduction, the CGPS covers Galactic longitudes from L=74.2 to 147.3 degrees and latitudes from B=-3.6 to +5.6 degrees. But where is that?

The 73° × 9° survey area runs along the path of the summer Milky Way, from the heart of Cygnus the Swan (also known as the Northern Cross) to a point about 15 degrees beyond Cassiopeia (the ``W'' that circles the North Star opposite the Big Dipper). This region of the sky is easiest to see on late summer and early fall evenings from mid and upper latitudes in the northern hemisphere.

The map below shows the location in the sky of the long, rectangular CGPS field, as seen from Calgary, Alberta at 9pm on October 15th. The north horizon is at the top, south at the bottom, east at the left, and west at the right. The Galactic Plane is marked in red. Major star magnitudes and colors are indicated. Constellations are in yellow. A larger version of this image, with star and constellation names and deep sky objects added (green), is available by clicking on the map. The other images on this page also have larger versions accessible in the same way.

XEphem map courtesey software developed by E. C. Downey.

Location in the Milky Way

Our Milky Way Galaxy is a large disk-shaped collection of stars with a diameter of approximately 100,000 light years (gas and other nonstellar matter extend considerably beyond this). Superposed on this disk is a broad spiral pattern. Many other galaxies in the universe have a form similar to our own. This photograph of the galaxy Messier 83 gives a rough idea of what ours might look like if we could see it from the outside.

While we don't really know how our Milky Way looks from a distance, we can speculate based on current information. These schematic plan views attempt to show our galaxy as an outsider might see it.

An edge-on view of another spiral galaxy, NGC 891, shows starlight from the disk absorbed by dark clouds of interstellar dust within the spiral arms.

Digitized Sky Survey image obtained through SEDS

We see a similar effect in the appearance of our own Milky Way, though of course it extends 360 degrees around the sky, since we are inside it -- our Sun lies about 30,000 light years from the center. The following panorama shows the entire Milky Way from our internal perspective, with the bright glow of the Galactic center in the middle of the picture, and the right and left edges corresponding to the direction 180 degrees away from the center. The area of the Canadian Galactic Plane Survey is indicated by the orange and yellow boxes. Clicking on the map accesses a larger version with Galactic coordinate labels (longitude is horizontal, latitude vertical).

Karma image annotation courtesey software developed by Richard Gooch

This Milky Way image, and expanded versions below, is composed of scanned photographs originally taken by S. Laustsen, C. Madsen, & R. West (1987, Exploring the Southern Sky, Springer-Verlag: Berlin) which have been reprojected, combined, and generously made available by the Astrophysics Data Facility at NASA's Goddard Space Flight Center on their marvelous Multiwavelength Milky Way site.

Coverage and Datasets

In the previous illustration, the yellow box shows the 73° × 9° survey area quoted above, which defines the boundary of the major high-resolution CGPS dataset: radio 21cm continuum and H line maps. The orange box indicates the area covered by somewhat lower-resolution 74cm continuum maps. In the enlarged view below, these are compared to the angular coverage of the other two major datasets: 2.6mm line CO maps (magenta) and 12-100 µm dust emission maps (red). See the Introduction for more information on the types of data.

Karma image annotation courtesey software developed by Richard Gooch

As the CGPS data is processed, it is organized into a collection of square mosaic images covering the survey area. These are shown in the following figure. All principal datasets will be projected into a set of 36 overlapping mosaics (yellow), each about 5 degrees across. In addition, the low-resolution 74cm data will also be projected into a set of 6 larger overlapping mosaics (orange), 15 degrees in size. After a short proprietary period, all of these data will be made available at the CADC for use by anyone interested.

[Map showing CGPS final release mosaics]

Karma image annotation courtesey software developed by Richard Gooch

Constellations (green) have been added for reference. The names of these are given in the larger version available by clicking on the one displayed.

The status of observation and data processing is given on our Status page. Some of the currently processed data can be viewed in the Image Gallery.

A Note on Angular Size

The moon's apparent diameter is 1/2 degree. The average person's fist (not including the thumb) covers 7 or 8 degrees when held at arm's length. Thus the region marked in yellow is about 1 fist wide and 9 or 10 fists long. This is quite a large area for an astronomical survey as detailed as the CGPS, even though it only touches a few constellations. A display showing the full 1-arcminute resolution of the entire survey when it is completed will require an image of 8800 × 1100 pixels -- about seven times the width of a conventional 1280 × 1024 computer screen!

Return to the CGPS page.