Home sweet home I
Our own galaxy is shaped as a large thin disc with a central bulge. If we could look to the disk form above it would appear as a large bar spiral. Most of the visible objects are located in that disc which is remarkable thin compared to other galaxies. It is surrounded by a weak halo containing stars and globular clusters.
Our solar system is located far outside the central region of the disc and near to its central plane. The glowing band of the Milky Way is the projection of this disc on the night sky. It consists of millions of remote stars and other objects. Most visible stars, nebulae and star clusters above or below the band are objects quite near to the sun. The brightest and most spectacular regions of the Milky Way indicate the direction to the center of the galaxy. They are located in the constellations Carina, Norma, Scorpius, Sagittarius and Scutum.
The Milky Way is mainly formed by stars, cold and invisible molecular clouds and mysterious Dark Matter. Gravitational forces acting between these objects while they are rotating around the center of the galaxy. The overall structure of our galaxy is a result of these forces combined with ongoing star formation processes: New stars are born in the dense regions of interstellar matter. The most massive of them ionize Hydrogen in their neighborhood forming reddish glowing nebulae. At the end of their short lifetime they explode as Supernovae and mix up gas and dust clouds and enrich their surroundings with heavy elements like metals. Shock waves may stimulate new star formation. Dust particles are created in the cool outer regions of red giant stars. Dust clouds have large impact on the visible appearance of the Milky Way. Dust absorbs visible light very efficiently. Most of the objects that we can see in the arms of the Milky Way are only a few thousand light years apart whereas the galactic center is invisible for our eyes.
The image covers a field of about 65x45° in the sky. Most deep sky objects are in the neighborhood of our sun, just 4,000 – 7,000 light years away. Some “holes” in the dust clouds allow us to have a deeper view into the galaxy: The Sagittarius cloud M 24 is part of the second next spiral arm, the Norma arm, 12,000 – 16,000 light years away. The globular cluster NGC 6522 shines through the so called Baade window - it is located beyond the galactic center.
Starting from the impressive star clusters M 6 and M 7 the bright HII regions M 8, M 20, M 17, M 16 and NGC 6604 form a chain in Northern direction. Additionally many open clusters are visible in the band of the Milky Was whereas some globular clusters outside the band are located in the halo ot the galaxy. The striking and colorful Antares region is quite near to us – here, the giant star Antares ionizes surrounding gas clouds and produces dust particles.
