Celestia Forums

Did you ever wondered how many stars are there in some specific direction? Well, I did. In the image below, this number is color-coded per "square" degree (image is 360x180 RA/dec map):



You can clearly see two sines. If one is Milky Way, what is 2nd one? Is it hipparcos satellite trajectory or what?

The stars in the Hipparcos HIP catalog were chosen by astronomers before the satellite was launched, so you shouldn't find any trace of the satellite's orbit in the plot, except, perhaps, if you carefully investigate the errors in the measurements.

I'd suggest plotting the positions in galactic coordinates to see how that looks.

I've just made another map, with number of stars mapped in blue, temperature in green and sqrt(radius) in red (this time not entirely accurate, because GIF only allows 256 combinations of colors):

i would think the other sin is space dust i the ecliptic plane
but i'm absolutely unsure of that.

Where there is more dust, rocks and other pieces of solar system (e.g. ecliptic plane) there is less opportunity to see stars. Maybe the sine represents the region that is furthest away from the ecliptica.