In And Out The Window

Here's a photo I took recently of the Milky Way with the constellations of Sagittarius and Scorpius over the rocks of Joshua Tree National Park:

It was taken with my iPhone using a new, free app for iOS called Nocturne. 

Above those majestic rocks you can see the light of countless stars and the dark silhouettes of cosmic dust clouds. The exact center of the Milky Way is in this general direction, but we can't actually see it. There's so much gas and dust there that the center is invisible to everything except telescopes that can see into the infrared and longer wavelengths (such as radio waves). 

Yet there is an area known as Baade's Window that is somewhat clear of dust and gas allowing us to see objects that are almost as distant as the center of our galaxy. This window is roughly centered on a globular star cluster known as NGC 6522, which is one of two globular star clusters that can be seen in the image below:

This image, which was taken with my Unistellar eVscope, shows globular star cluster NGC 6522 (right of center) and a somewhat smaller globular star cluster known as NGC 6528 (on the left). Even though this view is looking through Baade's Window notice that there are some dark nebulae visible here, especially on the left side of the image.

Determining distances is a somewhat inexact science. Current estimates put the center of the Milky Way at around 26,000 light years from us while NGC 6522 is around 25,000 light years away. That puts it somewhat in the same neighborhood as the center of our galaxy.

Of course within the constellation of Sagittarius we can see things that are farther than the center of the Milky Way, but you have to look in a somewhat different direction. The Milky Way's gas and dust blocks our view across much of Sagittarius which is why astronomers interested in other galaxies have referred to the disk and center of our galaxy as the Zone of Avoidance. 

The image below shows something that is not just on the other side the center of our galaxy, it is actually outside of it.

Can you spot it? It is Barnard's Galaxy (NGC 6822), the large fuzzy area near the middle of the image. Barnard's Galaxy is a dwarf irregular galaxy that's located about 1.6 million light years away. Like the globular star cluster it is also in the constellation of Sagittarius, but it is not seen in the same direction as the plane of our galaxy and the Zone of Avoidance.

 Here's the same image as before, but cropped on the galaxy itself. Notice the two blue regions near the top of the galaxy. Those are vast gas clouds of gas (nebulae) within the galaxy. I am still impressed that I can catch them with a 4.5" telescope.

Sagittarius is a big constellation. This view from SkySafari Pro shows the locations of these objects. The globular star cluster is on the edge of the spout in the Teapot of Sagittarius and very much in the heart of the Milky Way. While Barnard's Galaxy (top, left) is well outside the Zone of Avoidance. If it were in a different part of Sagittarius we might not even know that it was there at all.