Celestia Forums

Hi,

Take a look a this image first: http://www.inf.ufsc.br/~formig/fringes.jpg.

Now the question. What possibly could be those fringes? I am using a big star data file from celestia motherlode. In the image, I am viewing from above the plane of the galaxy, with magnitude limit set to max and stars as points. Could it be a celestia "unwanted introduced" visual effect? Or could it be a real star patter in our galaxy?

Giovanni

They're caused by limitations in the accuracy and precision of the distances to the farther stars. Remember that distance is determined by the parallax, not by direct measurements. It's a very tiny motion on the sky for extremely distant objects. This paralax gets tinier and tinier with larger and larger relative errors for stars that are farther and farther away. If you're measuring a parallax to the nearest milli-arc-second, the most distant stars that you can measure have a parallax of 0.001 seconds and the next most distant have a parallax of 0.002 seconds (one or two milli-arc-seconds).

An exercise for the student: how many light years is that difference?

selden wrote:They're caused by limitations in the accuracy and precision of the distances to the farther stars. Remember that distance is determined by the parallax, not by direct measurements. It's a very tiny motion on the sky for extremely distant objects. This paralax gets tinier and tinier with larger and larger relative errors for stars that are farther and farther away. If you're measuring a parallax to the nearest milli-arc-second, the most distant stars that you can measure have a parallax of 0.001 seconds and the next most distant have a parallax of 0.002 seconds (one or two milli-arc-seconds).

An exercise for the student: how many light years is that difference?

Excellent excercise

Very interesting! About the exercise, I found out ~1635 ly.