English: The brightest x-ray object in this scene is an unknown object at the upper left. The next brightest thing seems to be a distant active galaxy nucleus (AGN) coincidentally positioned just above the nebula. In third place comes NGC 604 itself. It's hard to compete with an AGN, but these young stars are doing an admirable job. X-rays are generated when things get super hot, and that's what's happening within the cavernous interior bubble of the nebula.

There's a better explanation and additional imagery at Chandra's website here: chandra.harvard.edu/photo/2009/n604/

This image was possible thanks to data from the following Chandra proposal: The Giant Extragalactic Star-Forming Region NGC 604

In addition, all HST proposals listed under this image were also used: https://www.flickr.com/photo.gne?short=S5kLbG

Chandra data: Violet / Magenta overlay: ACIS .30-7.00 keV

PHAT data: Red: WFC3/IR F160W Yellow-Green: ACS/WFC F814W Cyan: ACS/WFC F475W Blue: WFC3/UVIS F336W

WFPC2/WFC data: F673N, F658N, and F656N combined together into a pinkish "screen" layer

North is NOT up. It is 90° clockwise from up.