Recycling Matter in the Universe. X-ray observations of SBS 1150+599A (PN G135.9+55.9)

We present X-ray observations of the close binary nucleus of the planetary nebula SBS 1150+599A obtained with the XMM-Newton satellite. Only one component of the binary can be observed in optical-UV. New X-ray observations show that the previously invisible component is a very hot compact star. This finding allows us to deduce rough values for the basic parameters of the binary. With a high probability the total mass of the system exceeds Chandrasekhar limit and makes the SBS 1150+599A one of the best candidate for a supernova type Ia progenitor.