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Galactic Navigation
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Longitude & SCO X-1

Lets compare the location of Sco X-1 on the black and white map to the location of Sco X-1 on this diagram. Where is it on the black and white map? It is in the center, above the galactic plane. Does this mean that it is not in the Milky Way? Not necessarily.

The universe on a flat screen

Look at the location of Sco X-1 in the Degrees Longitude diagram. It is nearly at 0o. It is in the direction of the galactic center; similarly, it is near the center of the black and white map.

Longitude Diagram of the Earth

Do you see now why it seems to be so far above the galactic plane? It is very close to the Earth. The latitude of Sco X-1 is about 24o. Where would you draw it on the Degrees Latitude diagram?

Latitude Diagram of the Earth

Longitude & the Crab Nebula

Now lets compare the locations of the Crab Nebula. On the black and white map, it is the bright orange source all the way to the right.

The universe on a flat screen

On the Degrees Longitude diagram, it is near 180o.

Longitude Diagram of the Earth

Now imagine yourself standing on Earth and looking at the galactic center. Suppose you want to then look at the Crab Nebula. You would have to either go to the other side of the Earth to see it (because you can't see through the Earth!), or you would have to wait for the Earth to spin around so that you are facing the opposite direction. Why do you think you won't be able to see the Crab Nebula if you are looking toward the galactic center?

(hint: compare the location of the Crab on each diagram: Degrees Longitude, Degrees Latitude diagram and Black and White map)

Wrapping It Up

Imagine the night sky as a piece of black paper that is wrapped around the Earth. The seam of the paper (where the edges are taped together) is at 180o. The Crab Nebula would be close to the seam since it is close to 180o. Imagine someone pulling the tape off and laying the paper flat on a table. Now where would the Crab be? It would be near the right side of the paper, just as it is on the black and white map!

The universe on a flat screen

The black and white map tries to show all parts of the universe on a flat screen.

View the Chandra Sky Map in our Photo Album!

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