New Mass Limit for White Dwarfs: Super-Chandrasekhar Type Ia Supernova as a New Standard Candle

Type Ia supernovae, sparked off by exploding white dwarfs of mass close to the Chandrasekhar limit, play the key role in understanding the expansion rate of the Universe. However, recent observations of several peculiar type Ia supernovae argue for its progenitor mass to be significantly super-Chandrasekhar. We show that strongly magnetized white dwarfs not only can violate the Chandrasekhar mass limit significantly, but exhibit a different mass limit. We establish from a foundational level that the generic mass limit of white dwarfs is 2.58 solar mass. This explains the origin of overluminous peculiar type Ia supernovae. Our finding further argues for a possible second standard candle, which has many far reaching implications, including a possible reconsideration of the expansion history of the Universe.

Figure 1

Equation of states. The solid line represents Chandrasekhar’s equation of state (corresponding to zero magnetic field and hence infinitely many Landau levels). The dotted and dashed lines represent the 5-level (corresponding to a very strong magnetic field) and 1-level (corresponding to the ultimate equation of state for an extreme magnetic field) systems of Landau quantization, respectively. $E_{F\max }=200m_e{c}^2$.

Figure 2

Mass-Radius relations. The pure solid line represents Chandrasekhar’s result and the one marked with filled circles represents the evolutionary track of the white dwarf with the increase of the magnetic field. The dot-dashed, dotted, and dashed lines represent the white dwarfs with 50 124-level, 200-level, and 1-level systems of Landau quantization, respectively (corresponding to increasing magnetic fields). $E_{F\max }=200m_e{c}^2$.