Neutron Stars and Special Relativity and General Relativity Here is a question which I can't quite wrap my head around: Suppose we have a Neutron Star that is borderline on the Chandrasekhar limit in its rest frame. In another frame, the Neutron star is moving. As a result, its density increases due to 1) Relativistic mass increase. 2) Length contraction. So why does the Neutron star not form a black hole? Technically, this question would apply for any object in any frame of reference that is moving sufficiently quickly. So what am I missing here? I suppose a general relativistic explanation is that Stress-Energy is a tensor, so matter what coordinate system you use, the criteria for black hole formation will not be met. So, 1) Is this question well posed? 2) Where does special relativity break down? 3) Did I answer my own question? 4) What is the General Relativistic explanation? I would like to hear your input. Thanks.