Context: A detailed study of the evolution of the supernova SN 2023zcu, discovered in 2023 at the edge of the spiral galaxy NGC 2139, located approximately 90.7 million light-years away from Earth, can help estimate the distance of the local universe.
Supernova:
- A supernova is the name given to the cataclysmic explosion of a massive star.
- Supernovae (SNe) are one of the most violent explosions in the universe.
- It can emit more energy in a few seconds than our sun will radiate in its lifetime of billions of years.
- These spectacular events can be so bright that they outshine their entire galaxies for a few days or even months.
- They’re also the primary source of heavy elements in the universe.
Types of Supernova:
Core-collapse supernovae (CCSNe):
- These are one of these cosmic fireworks occurring when a massive star exhausts its nuclear fuel and can no longer support itself against the gravitational pull.
- The most common type of core-collapse supernova is Type IIP, which happens when a massive red supergiant star (about 8–17 times the mass of the Sun) reaches the end of its life.
- Process: When the star’s core collapses into a proto-neutron star, the outer material falls inward, then bounces back from the surface, creating a powerful shock wave.
- When the shock reaches the surface, the star’s outer layers break away and expand into space.
- The supernova becomes brightest soon after this. As these layers keep expanding, they slowly cool down and lose energy—this stage is called shock cooling. After this, there is a phase lasting a few months when the supernova remains opaque.
- The supernova’s distance is estimated to be about 27 Mpc using the Expanding Photospheric Method (EPM). This method calculates distance by comparing the actual size of the expanding surface of the supernova with how bright it appears.
Thermal runaway supernova:
- It can occur when two stars orbit each other, and one or both of those stars is a white dwarf.
- If the stars in one of these binary systems collide, or if one of the white dwarfs absorbs enough matter from the other star, the white dwarf can become a supernova.
Bolometric luminosity:
- It is the total energy a supernova emits across all wavelengths of light, from ultraviolet to infrared, giving a full measure of its brightness.
- By modeling the bolometric luminosity, scientists estimate that the original star had a mass of about 12 times that of the Sun and an explosion energy of about 2 × 10⁵¹ ergs. These values are typical for explosions of red supergiant stars.