ASTR 130, O'CONNELL. [Fall 2008] Lecture Notes

ASTR 130 (O'Connell) Lecture Notes

THE MILKY WAY:
Our Galaxy from the Inside

The panoramic image above is a drawing constructed from photographs by Knut Lundmark at the Lund Observatory in Sweden. It maps the appearance of the entire sky (360 degrees) in Galactic coordinates, in which the plane of our Galaxy defines the equator. The picture is centered on the direction to the Galactic center. The dark lanes or "rifts" are obscuration caused by dust clouds lying in the plane.
You can identify a number of familiar features in the picture once you get your bearings. Compare it to the Galactic charts in Norton's Star Atlas.

Sagittarius and Scorpio are in the center of the image, but their bright stars are mostly hidden in the glow of the light of millions of fainter stars in the plane.

The brightest star in the image is Sirius, lying just below the plane near the right hand edge of the image. Orion lies to the right and below Sirius, tilted toward the right. You can see the three stars of Orion's belt pointing at Sirius. Directly across (above) the plane from the belt are Castor and Pollux, the two brightest stars in Gemini.

The part of the Milky Way that is visible in the summer sky runs from the center to about 3/4 of the way to the left hand edge. Vega and its constellation Lyra can be seen lying above the plane about halfway from the center to the left hand edge. Cygnus is in the Milky Way, just below and left of Lyra.

The three stars at the extreme left hand edge of the image, just above the plane, are in Auriga. The brightest is Capella. This section of the Milky Way is visible in autumn and winter.

Click here for a wide angle picture of the northern Milky Way with the bright constellations identified.

The two cloudy patches below the plane and just right of center are the Magellanic Clouds (only visible from the southern hemisphere). They are external galaxies. M31, the bright galaxy in Andromeda, is visible as a streaklike feature below the plane about 1/6 of the way from the left hand edge.

Compare the Lund drawing with this modern, color mosaic photograph which is presented in the same format.
All of the above views are (obviously) from the Earth's perspective. For a different perspective, click here for a view (5000 light years wide) of the Sun's location in the Galaxy together with identifications for a number of bright stars and other features. This is part of the Richard Powell Atlas of the Universe, a pictorial "zoomout" from the Solar System.

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Last modified October 2008 by rwo

Panoramic Milky Way image from Lund Observatory. Northern Milky Way photo by J. Lodriguss. Text copyright © 2000-2008 Robert W. O'Connell. All rights reserved. These notes are intended for the private, noncommercial use of students enrolled in Astronomy 130 at the University of Virginia.