One of the sights never seen in brightly lit city skies, but nearly unforgettable in a truly dark sky, is the Milky Way, a band of faintly glittering stars spanning the heavens from horizon to horizon, most spectacularly at a certain time of night (in the early evening in mid to late summer, and a couple of hours later each month after that). The Milky Way consists of the combined light of hundreds of thousands of stars, too far away and too faint to be seen as individual stars, scattered over a disc-shaped region thousands of light years across. Most images of the Milky Way are copyrighted by the person who took them, but as it happens the National Parks Service has been pursuing a program of night-sky photography to illustrate the degradation of the appearance of the sky caused by light pollution which can be used by non-commercial sites such as this one, so long as credit is given where credit is due. The photo below is half of a 360-degree panoramic image taken from the top of Mount Whitney for the light pollution survey. It shows the Milky Way arching upward from one horizon, passing nearly overhead, then arching downward to the opposite horizon. The right (southern) side of the cropped image shows the region near Scorpius and Sagittarius, which is in the direction of the center of our galaxy; the top of the arch passes through the Summer Triangle, while the left (northern) side dips downward through Cassiopeia. The bright object below the right side of the Milky Way is the planet Jupiter, while the Andromeda Galaxy faintly shines below the left side of the arch. Clicking on the image opens a page which shows a larger version of the entire panorama. (There is also a beautiful false-color version of the arc of the Milky Way on the Astronomy Picture of the Day page for Dec 25, 2009, which cannot be shown here because of copyright considerations.)
The Milky Way arching over Mount Whitney, near 18 hours Local Sidereal Time.
(D. Duriscoe, C. Duriscoe, R. Pilewski, & L. Pilewski, U.S. NPS Night Sky Program, apod090827)