Thus, X-ray observations are a good way to find the stellar members of a young association like Upper Scorpius. The next image shows a wide field X-ray image of the full Scorpius Centaurus association, of which the Upper Scorpius association is the youngest part. One can see a clear enhancement in the density of X-ray sources associated with these three subgroups of the association. In the next step of our study we have determined the ages and masses of about 100 low-mass members in Upper Scorpius. About 12 Myr ago the most massive star in Upper Centaurus-Lupus exploded as a supernova, creating a large shock wave.
Further work is in progress.