Nova Explosion

In September, astronomers predict a rare nova explosion ( explosion of T Coronae Borealis) will brighten our night sky.

T Coronae Borealis

• T Coronae Borealis is known as the “Blaze Star” or “T CrB.”
  • The T CrB nova was last observed from Earth in 1946.
• This event will occur approximately 3,000 light-years from Earth.

What is a Nova Explosion?

• A nova explosion occurs when a star explodes due to its interaction with a nearby star.
• Explosion Trigger: When the heat and pressure become excessive, a thermonuclear explosion occurs.
• Brightness Change: This explosion makes the white dwarf appear much brighter in the sky.
• Post-Explosion: After the explosion subsides, the star returns to its original brightness.
• Mechanism: It is a recurring event during the prolonged death of two neighbouring stars within the same system.
• Visibility of the Nova
  • Naked Eye Observation: The nova can be seen without a telescope for about a week.
  • Appearance: During this time, it will look like a new star has appeared in the sky.

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About Nova

• Origin of Name: The term “nova” comes from the Latin word for “new.”
•  A nova is a transient astronomical event.
  • In this event, a new bright star appears suddenly and then fades over weeks or months.
• Nova occurs with a system of two stars.
  • Red giant 
  • White dwarf
    • It revolves around each other. 
• White dwarf attracts matter from red giant’s atmosphere when they are close
  • This causes nuclear explosions and ejection of gases. 

Causes and Characteristics

• Star Involvement: All observed novae involve white dwarfs in close binary systems.
• Variations: The appearance of a nova depends on the circumstances of the two progenitor stars.
• Main Sub-Classes: Novae are categorised into classical novae, recurrent novae (RNe), and dwarf novae. All are types of cataclysmic variable stars.

About Supernova

• A supernova is the explosion of a massive star.
• Main Types of Supernovae
  Supernovae are broadly categorised into two main types based on their explosion mechanisms.
  • Type 1: Thermonuclear Runaway (Type Ia SNe)
    • Occurrence: Happens in binary star systems where at least one star is a white dwarf.
    • Mechanism: The white dwarf undergoes a thermonuclear explosion.
  • Type 2: Core-Collapse
    • Occurrence: Occurs in stars with masses greater than eight times the mass of our sun.
    • Mechanism: The star collapses in on itself and explodes.
• Subtypes of Supernovae
  • Classification by Spectra: Each main type has various subtypes, which are classified based on the elements observed in their spectra.

Causes of Supernovae 

1. Supernova from a Dying Massive Star

• One type of supernova occurs when a massive star ends its life with a huge explosion.
• Mass Requirement: This happens in stars at least five times the mass of our sun.
• Fuel Consumption: Massive stars burn a lot of nuclear fuel in their cores, producing immense energy and heat.
• Balance of Forces:
  • Gravity: Tries to compress the star into a tight ball.
  • Nuclear Pressure: The burning fuel creates outward pressure, balancing the inward pull of gravity.
• Collapse and Explosion:
  • When the star runs out of fuel, it cools, reducing pressure.
  • Gravity takes over, causing the star to collapse rapidly.
  • This rapid collapse creates shock waves, leading to an explosion of the outer part of the star.

2. Supernova from a Binary Star System

• Binary Systems: Another type of supernova can occur in systems where two stars orbit each other.
• White Dwarf: Involves at least one Earth-sized white dwarf, the remnant of a star similar to our sun after it has run out of fuel.
• Collision or Accretion:
  • If a white dwarf collides with another star or accumulates too much matter from its companion, it can explode.
  • This explosion is a powerful event, resulting in a supernova.

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Difference between Nova and Supernova

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