As the human explorers ventured into an uncharted system, they got the feeling that their presence was expected. In fact, the stars themselves greeted them.

What was the greeting?

• Is zooming in required? – McMagister Jan 4 '15 at 1:21
• @McMagister Nope. – Tryth Jan 4 '15 at 4:47
• Brilliant Question! – Rafe Jan 5 '15 at 6:44

The mesage is

Peace

Explanation

Juxtapose the image and a 180 degrees rotated version of the image, then remove all the stars that appear in both images, and the word "Peace" is formed twice.

"Z", because if you highlighted all the stars that are not square, you get a "Z".

• Congratulations. You were 5min faster than me. Well done! – BmyGuest Jan 4 '15 at 8:32
• Edit your answer with the correct one and I will remove my answer leaving the "Z" interpretation. – McMagister Jan 4 '15 at 8:35
• Nei, it's fine as it is. It's not a race - but an excellent puzzle. – BmyGuest Jan 4 '15 at 8:39

I think what the starts try to tell humans simply is

Turn around!

the reason being:

There is a 2-fold rotational symmetry in the image, I.e. You can turn it around by 180 degrees and it is the same...

Other interpretations like "your future is like your past" or "look behind you before going onward" etc. are also possible, but I took the first one which jumped to head...

Edit: On closer inspection (now with a computer at hand)

The image is not 100% rotational symmetric. Only some stars are. The following image highlights this in colour

Red --> Original stars
Green --> 180degree rotation stars
Yellow --> 180degree rotation overlapping positions

Therefore I might need to look a bit deeper...

Ignoring the 'yellow' parts leaves only dots which - rotated by 90 degrees' spell out PEACE.