The Milky Way
Another feature in the sky, especially at very clear nights, is the Milky Way, a band of many stars. That lane across the sky shows us the Galactic Plane, the disk of the Milky Way galaxy. It shows us the galactic plane, that makes an angle of about 60 degrees with the ecliptic.
The Milky Way is a barred spiral galaxy with a diameter of at least 150,000 lightyears, although a halo of dark matter around it extends to many times further out. The disk is between 100 and 10,000 light years thick. There are at least 400 billion stars in the galaxy of which our Sun is just one.
Some parts of the Milky Way appear dark, as if there are few stars in that region. This is only apparent, it is caused by large clouds of hydrogen and stellar dust, that block the visible light. In the southern hemisphere we can see the centre of our galaxy in the constellation of Sagittarius.
Reconstruction of the Milky Way galaxy, based on what we have observed in many different wavelengths. Our Solar System is located somewhere in one of the outer spiral arms, the Orion arm.
Where does the name “Milky Way” come from?
The word Galaxy is related to the Greek word for milk “gala”. They called it Galaxias Kyklos (“Milky Circle). The Romans translated that into Via Lactea meaning “Milky Way”.