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We know that a moderately massive star, including Sun, is converted
to a compact object white dwarf, when its nuclear fuel stops burning. The more
massive stars become neutron stars and black holes when their nuclear fuel
is exhausted. Indian-American Physicist Subrahmanyan Chandrasekhar showed
that the maximum mass of a nonrotating, nonmagnetized white dwarf, consisting
mostly of carbon-oxygen, is 1.4 solar mass, called Chandrasekhar limit.
By gaining mass beyond this value, a white dwarf explodes leading to a type Ia
supernova (SNIa), hence any SNIa always will have a fixed luminosity. This
helps SNIa to be considered as a standard candle. This further helps them
considering to understand the evolution history of universe. However, over the
last few decades, there are type Ia supernovae (SNeIa) identified with
unusually high luminosity violating Chandrasekhar limit significantly.
Naturally, this has far reaching implications cautioning (all) SNeIa to be
standard candle. Over more than a decade, along with my group members,
I have been exploring the possible routes to the violation of Chandrasekhar
limit and possible new mass-limit(s). The potential reasons behind such
a violation could be magnetic field, modified gravity, noncommutative spacetime
etc. Many other groups also, following our initiation, showed similar violation
based on alternate physics. I will attempt to review this topic and its
evolution, by theory and numerical simulation along with stellar evolution.
I will also enlighten its implications opening a question, how sacrosanct the
Chandrasekhar limit is? |