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Q&A: Miscellaneous X-ray Sources

Q:
The Chandra Deep Field images, North and South, show objects as they appeared billions of years ago. If we had a magical correspondent in one of those distant galaxies, they would tell us that things are very different now, than in our recent photos. However, could one in the North Field see the ones in South Field?

A:
Yes, if we had a correspondent with a special telephone which could transmit voices instantaneously, they would tell us that things are quite different today. Many stars and galaxies will have been born, many mergers will have taken place, many stars and galaxies will have died.

According to the distance of the faintest objects in each fields, you are correct in assuming that an observer in the north could not have communicated with an observer in the south - it would take somewhat less than double the age of the Universe for light to travel from one to the other.

Note that the Chandra Deep Fields are approximately 135 degrees apart in the sky, not 180 degrees, so the distance between them is shorter than adding the distance to the furthest object in the north field to the distance of the furthest object in the south. The coordinates for the fields are found on the latest Chandra Deep Field release:
http://chandra.harvard.edu/photo/2004/goodsbh/

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