The recent discovery of the fastest spinning white dwarf, named J0240+1952, by a team of astronomers has brought forward exciting new revelations about these fascinating celestial bodies. This white dwarf completes a full rotation once every 25 seconds, an impressive pace that has captured the interest of the scientific community.
About J0240+1952 and its Unique Magnetic Propeller System
J0240+1952 is part of a binary star system wherein it pulls material from its larger companion star in the form of plasma due to its immense gravity. This is a process guided by what’s known as a magnetic propeller system. The interesting aspect here is the interaction between this accumulated plasma and the white dwarf’s magnetic field. The latter acts as a protective barrier, repelling most of the plasma away from the white dwarf.
Explaining White Dwarfs
White dwarfs are stars that have exhausted their hydrogen, previously used as nuclear fuel. These celestial entities have incredibly high densities. On an average, a typical white dwarf will be half the size of the Sun yet have a surface gravity 100,000 times that of Earth. When a star like our sun uses up its core hydrogen in nuclear fusion reactions, producing helium, there is a heat generation and outward pressure. However, this pressure is balanced by the inward push of the star’s own gravitational force. Once the hydrogen depletes and fusion slows, gravity forces the star to collapse into a white dwarf.
The Transition to Black Dwarfs
With time—stretching over tens or even hundreds of billions of years—a white dwarf will cool down and transform into a black dwarf, which emits no energy. Notably, the universe’s oldest stars are only10 billion to 20 billion years old. Hence, no black dwarfs are known to exist. Importantly, not all white dwarfs evolve into black dwarfs. Those with sufficient mass reach a point known as the Chandrasekhar Limit.
The Chandrasekhar Limit
The Chandrasekhar Limit is the maximum mass theoretically possible for a stable white dwarf star. This limit—approximately 1.4 times the mass of the Sun—states that a degenerate object with greater mass must inevitably collapse into a neutron star or black hole. This concept was first proposed in 1931 by Nobel laureate Subrahmanyan Chandrasekhar, who later won the Nobel Prize in Physics in 1983 for his notable contributions to the understanding of the physical processes involved in the structure and evolution of stars.
Last Modified: February 13, 2024