EXPOSING THE STUFF BETWEEN STARS:

EXPOSING THE STUFF BETWEEN STARS: A Panorama Canadian Galactic Plane Survey Mapping Our Milky Way Galaxy

Map 1 displays the stuff between stars in the Perseus Spiral Arm of our Milky Way Galaxy by assigning different colours to radiation not detected by the human eye. Invisible to optical telescopes, hydrogen gas can only be revealed by observations of faint radio waves emitted at a wavelength of 21 centimetres. Besides radio data showing this gas, from the National Research Council of Canada's Dominion Radio Astrophysical Observatory (and assigned colour combinations of blue, orange, yellow, and green), this composite image includes Infrared Astronomical Satellite (IRAS) data (coloured pale pink), and data (grey-blue) from the Westerbork Synthesis Radio Telescope (WRST) in the Netherlands.

The location on the night sky of this panoramic strip (2000 light-years across) is displayed in Diagram 1 while its position in the Milky Way relative to our Sun is presented in the ``top view'' schematic in Diagram 2.

The diffuse nebulosity that fills the Map 1 panorama from left to right is hydrogen gas, which is distributed along the mid-plane of the Galactic disk and runs across the middle of the image. However Canadian Galactic Plane Survey astronomers used the DRAO array to isolate the gas in the Perseus Arm, 6500 light-years distant, from the rest of the gas in the disk. Overlaid on these hydrogen data are IRAS images of the dust that intersects our line of sight through the disk. The point-like sources (WRST) are mainly distant galaxies that have very energetic cores called Active Galactic Nuclei.

Far from a homogeneous environment, the interstellar medium in the Perseus Arm shows a highly disturbed and seemingly chaotic appearance. This region has been shaped partly by the ongoing formation of massive, hot stars near the hot dusty clouds (appearing pink) of the W3, W4 and W5 regions right of centre, and perhaps also by the passage of a large scale spiral shock wave as the matter in the Perseus Arm orbits around the centre of the Galaxy.

MAP CREDIT:

Jayanne English (U. of Manitoba) using data acquired by the Canadian Galactic Plane Survey (NRC/NSERC) and produced with the support of Russ Taylor (U. of Calgary).

• Full Resolution Tiff (17 Mbytes)
• Data: H I (DRAO), 92 cm continuum (Westerbrok), 60 micron (IRAS)
• DRAO fields: MV, MW, MX and MY
• Full Caption in ascii format

LOCATION ON THE SKY: The Perseus Spiral Arm Region of our Milky Way Galaxy which is shown in the Canadian Galactic Plane Survey's January 2000 Panorama.

This is 1 of 2 diagrams which show the location of the Canadian Galactic Plane Survey's Map 1 (press release CGPS pr_14012000).

Optical image of a section of sky near the plane of the Milky Way. Constellations are drawn in and around this section to show its location on the sky. The area of the large CGPS panoramic image (MAP 1) is marked. Note this is only the eastern 25% of the survey; the rest extends through Cassiopeia and into Cygnus, including the conspicuous North America Nebula just below the Swan's tail. Most of the bright areas are swarms of stars concentrated in the Galactic plane. Also concentrated in the plane are numerous clouds of gas and dust. The dust absorbs starlight behind it to produce the dark patches in this image. At infrared wavelengths, these dark clouds glow as the dust reradiates the absorbed energy as heat. At radio wavelengths, the gas itself becomes visible. The CGPS images show both gas and dust in the Galactic plane in radio and infrared light.

CREDIT: The optical Milky Way plane view 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 combined and made available by the NASA Astrophysics Data Facility.

LOCATION IN THE MILKY WAY GALAXY: Schematic of Our Milky Way Galaxy which Shows the Region Mapped in the Canadian Galactic Plane Survey's January 2000 Panorama.

This is the second of 2 diagrams which show the location of the Canadian Galactic Plane Survey's Map 1 (press release CGPS pr_14012000).

Schematic top view of our home galaxy, the Milky Way, showing the positions of the Sun and the major spiral arms according to present understanding. The Milky Way contains roughly 100 billion stars in a large disk 100,000 light years across. Most gas, dust, and newly forming stars occur in a set of spiral-shaped arms. The Local arm we inhabit is a relatively small one. The interstellar material revealed in the large CGPS panoramic image (MAP 1) lies mostly in the Perseus spiral arm. The area covered by this image is indicated. The entire CGPS is about four times larger, extending inwards (right) along the Perseus and Local arms.

CREDIT:

Schematic of the top view of the Milky Way galaxy is based on a model by J. Taylor & J. Cordes (Astrophysical Journal 1993, Vol. 411, P. 674) and follows the conventions in "The Guide to the Galaxy" (N. Henbest & H. Couper 1994, Cambridge University Press).