NGC7129 is a reflection nebula visually located in the constellation Cepheus. The blue color comes from the light from many young blue stars (more than 130 which are only a very few
million years old; for reference, our sun is about 5 billion years old) reflecting off the gas/dust of the region. The red crescents are
Herbig‐Haro objects. The relatively fine structure of the blue reflection nebula is a result
of the stellar winds caused by the energetic young stars pushing back the gas/dust cloud.
In the top right of the photo, you can see the bottom half of a nice open star cluster, NGC7142 (just above two tiny edge-on spiral galaxies; it is perhaps a symptom of how much gas/dust there is here that there are so few background galaxies).
This nebula is about 3300 light years away from us, and is about fifteen light years across at its widest point. The entire field of the uncropped image is about the same width as a full moon.
Copyright 2020 Mark de Regt