CHANDRASEKHAR LIMIT

Recently, an international team saw a white dwarf losing its brightness in 30 minutes, which usually takes a period of several days to months.
This peculiarity in brightness of white dwarfs can be referred to as switch on and off phenomena.
Using the Hubble Space telescope and Transiting Exoplanet Survey Satellite (TESS)astronomers have identified several white dwarfs over the years.

Important points:

White dwarfs are stars that have burned up all of the hydrogen they once used as nuclear fuel.
Such stars have very high density.
A typical white dwarf is half the size of our Sun and has a surface gravity 1,00,000 times that of Earth.
Stars like our sun fuse hydrogen in their cores into helium through nuclear fusion reactions.
Fusion in a star’s core produces heat and outward pressure (they bloat up as enormous red giants), but this pressure is kept in balance by the inward push of gravity generated by a star’s mass.
When the hydrogen, used as fuel, vanishes and fusion slows, gravity causes the star to collapse in on itself into white dwarfs.

Black Dwarfs:

Eventually – over tens or even hundreds of billions of years – a white dwarf cools until it becomes a black dwarf, which emits no energy. Because the universe’s oldest stars are only 10 billion to 20 billion years old there are no known black dwarfs.
It must be noted that not all white dwarfs cool and transform into black dwarfs.
Those white dwarfs which have enough mass reach a level called the Chandrasekhar Limit.
At this point the pressure at its center becomes so great that the star will detonate in a thermonuclear supernova (explosion).

Chandrasekhar Limit

Chandrasekhar Limit is the maximum mass theoretically possible for a stable white dwarf star.
A limit which mandates that no white dwarf (a collapsed, degenerate star) can be more massive than about 1.4 times the mass of the Sun.
Any degenerate object more massive must inevitably collapse into a neutron star or black hole.
The limit is named after the Nobel laureate Subrahmanyan Chandrasekhar, who first proposed the idea in 1931.
He was awarded the Nobel Prize in Physics in 1983 for his work on the physical processes involved in the structure and evolution of stars.

SOURCE: THE HINDU,THE ECONOMIC TIMES ,MINT

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