Cluster central object orbited by many small objects

Hi,

I want to cluster my data into 2 clusters:

one central body in cluster #1, all other particles in cluster #2.

Figures are attached showing my dataset. 'central_body.jpg' is a zoom in of 'all_data.jpg' in the area of large density just right to [0,0].

More than million particles are involve, so hierarchical clustering is not an option for me, due to memory and speed considerations.

The central body is also composed of particles.