A new Nature paper claims that a super-Chandrasekhar Ia supernova has been found, and that "Super-Chandrasekhar mass SNe Ia should preferentially occur in a young stellar population." This, obviously, could have implications for cosmology. These "new" supernovae can be identified spectroscopically, so such supernovae data can be checked for this new type. My guess is that isn't going to be enough to make a cosmological constant/dark energy go away. Edit: I meant to start this thread in the Astrophysics Forum, but I guees it's OK here.