l=0° indicates the direction to the centre of ourgalaxy. The direction to the centre of the Milky Way is at longitude 0 degrees and latitude 0 degrees.įigure 2: Colour map of the night sky with the Milky Way band and Galactic longitude directions highlighted. This bright band also coincides with the ‘equator’ of our sky coordinate system, in which we indicate directions to stars as their ‘galactic longitude’, which runs along the Milky Way band as indicated in the image below, and ‘galactic latitude’, which runs perpendicular to the Milky Way band (basically the same as geographic longitude and latitude used to locate places on earth).
The halo of our galaxy surrounds the disk.īecause of our position inside the Milky Way we see our galaxy’s disk edge-on and this leads to a concentration of stars along the bright band in the Gaia sky map. As explained in this item on the anatomy of the Milky Way, our galaxy consists of a flat disk with spiral arms and a thicker central part, consisting of the bar and the bulge. This band is caused by our view from inside our home galaxy, also called the Milky Way. The bright band running horizontally across the middle of the image is the Milky Way which can be seen at night if you are in a dark place. Credits: ESA/Gaia/DPAC - CC BY-SA 3.0 IGO. In the image below we see a colour map of the entire night sky constructed from the Gaia measurements of the positions of stars in the sky, as well as their brightness and colour.įigure 1: Colour map of the night sky constructed from Gaia data.
Where do the stars go? Where do they come from? Wavy proper motion patterns and the rotation of the Milky Way disk
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