Enormous effort has been expended to select and characterize members of the Orion Nebula Cluster, the richest young cluster near the Sun. Infrared telescopes have found nearly 2000 members ranging from a 45 solar mass O6 star to brown dwarfs with only 3 Jupiter masses.  The COUP image sees nearly all members with masses above ~0.2 solar masses, but only a portion of the lower mass objects.  However, it does capture several dozen previously unknown  young stars, mostly lower mass stars deeply embedded in the molecular cloud behind the bright nebula. 

Close-up view of the inner 5'x10' of the COUP field around the dense Orion molecular  cloud cores.  The background greyscale image shows the dusty cloud. The red plusses  indicate previously unknown flaring COUP sources which are certainly new young stars.  The green crosses are probably, but less confidently, also new members.  The black circles are thought to be contaminants, quasars from far beyond our Galaxy which are seen through the molecular material. 

Here are a few of the plots of X-ray variations, called lightcurves, of newly discovered Orion stars.   The X axis shows time during the 13-day COUP observation (five gaps occur when Chandra's orbit approaches Earth).  The dramatic flares, even in weak sources, are the signature of young stars.


The full paper on the COUP membership is:
Membership of the Orion Nebula population from the Chandra Orion Ultradeep Project
Konstantin V. Getman, Eric D. Feigelson, Nicholas Grosso, Mark J. McCaughrean,
Giusi Micela, Patrick Broos, Gordon Garmire, Leisa Townsley

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