Type Ia Supernovae
Overview of Supernovae
What is a supernova?
Plural · Supernovae
The term given to the moment a star explodes is a supernova. They are the biggest and most violent explosions scientists have identified, and they mark the end of a star's energy-producing life. A supernova is a cataclysmic event with the potential to outshine their galaxy for weeks or months.
There are three main types of supernovae (I, II, and III), and they are categorized into subtypes based on various characteristics. This website will focus on type Ia, known as the thermal runaway supernova.
Type Ia Supernovae are rare, occurring approximately once every 500 years in galaxies such as the Milky Way, compared to type II, which occurs about every 50 years in our galaxy.
How does a type Ia supernova occur?
Type Ia supernovae occur in a binary system when two stars orbit each other around a common mass and are, therefore, gravitationally bound to each other. For a Ia supernova to occur, one of the two stars must be a white dwarf; its companion star may be a red giant or a low-mass star, such as our sun.
A white dwarf is a small, dense star formed when a low-mass star exhausts its nuclear fuel and expels its outer layers, such as hydrogen and helium. White dwarfs are considered "dead stars" because they lack this nuclear heat source that gives stars life, and the “dead star” will cool, potentially for thousands of millennia.
A red giant is a star reaching the end of its life before transitioning into a white dwarf. It is vast, with low surface temperatures and high luminosity. The star’s core no longer contains hydrogen, preventing it from fueling nuclear fusion. The red giant’s outer layer expands dramatically due to extra heat, and its bloated surface gives it its red appearance.
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During the process of a type Ia supernova, a white dwarf gains matter from its companion star, such as a red giant, triggering a “runaway” reaction. Once the white dwarf's mass reaches the maximum mass possible for a stable white dwarf, which is 1.44 times the Sun's mass (The Chandrasekhar limit), it loses stability. At this stage, the white dwarf cannot support this additional material, and this results in a supernova.
There is evidence indicating that another scenario could lead to a Ia supernova. Astronomers believe that when two white dwarfs circle towards each other, they can merge, and if their joint mass exceeds the Chandrasekhar limit, they can become unstable. This, too, could result in a type Ia supernova. One important factor distinguishing type Ia supernovae from others is its absence of hydrogen.
Figure 1. the process of a type Ia Supernova
Astronomers have determined that in all cases, type Ia supernovae result in the complete destruction of the star, leaving behind only leftover energy, light, and elements forged through the explosion;those heavier than iron, such as magnesium and nickel.
In contrast to type Ia, type II supernovae are believed to be the birthplace of black holes and neutron stars.