Starship Asterisk*

Chris, Thanks, for the response. Yes, indeed, the true edge is as you have described. What I was trying to relate to my students was the apparent edge based on the 13.8 billion year age of the universe, as opposed to the edge that occurs due to the expansion of the universe since it was created. Eit...

I particularly liked this image because in 12 years of teaching astronomy, one thing I tried to get across to my students was that the universe was not so big as many tried to paint it, and that it was comprehensible. One way I tried to do this was to show them an image of the Andromeda galaxy. Then...

I heard from someone who contacted the author who admitted it was a ' composition'. APOD was supposedly told the same. Shame on APOD for not presenting this correctly.

This is an amazing image in its own right, but I want to point out something that is not mentioned in the caption -- there is clear visual evidence of an erosion terrace from a previously larger ice flow/body. We see such 'terraces' around the great salt lake in Utah, USA, but to see a very similar ...

OK, fair enough, they only mention 'likely', but I'm getting weary of this 'instant' science where pictures are said to depict things that are only conjecture or at best unproven theory such as dark matter.

I'll retreat to the background on this. No further replies are necessary.

The caption for today's image of Elliptical Galaxy NGC 1132 raises a question. The caption states that the X-ray image traces the location of the dark matter. How is this done/known? Up to now, my understanding of dark matter is it is theoretical and the only way that astronomers deduce it's presenc...