T CORONAE BOREALIS

Source: IndianExpress

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Context

• Astronomers are waiting for the fiery explosion of T Coronae Borealis, also dubbed the “Blaze Star” and known to astronomers as “T CrB”.
• It is expected to happen in September when a once-in-a-lifetime nova explosion 3,000 light-years from Earth will light up our night sky.

Details

T Coronae Borealis

• T Coronae Borealis (T CrB) is a binary star system located approximately 3,000 light-years away from Earth in the constellation Northern Crown (Corona Borealis).
• It is known for its recurrent nova explosions, making it a significant object of study in astronomy.

Binary Star System

• Components:
  • White Dwarf:The primary star, a dense remnant of a larger star, about the size of Earth but with the mass of the Sun.
  • Red Giant:The secondary star, nearing the end of its life cycle, losing hydrogen to the gravitational pull of the white dwarf.

Recurrent Nova Phenomenon

• Nature:T CrB is classified as a recurrent nova, which means it undergoes periodic nova explosions.
• Cycle:It erupts roughly every 80 years, with significant recorded events in 1866, 1946, and expected again around September 2024.
• Cause:The white dwarf accretes material from its companion star, leading to periodic thermonuclear explosions on its surface.

Historical Observations

• First Recorded Event:Historical records suggest sightings of T CrB's nova event dating back to 1866, with earlier possible sightings in 1217 and 1787.
• Astronomical Significance:These events have been noted for centuries, contributing to our understanding of stellar evolution and cataclysmic variables.

Nova Explosion Characteristics

• Appearance:During a nova explosion, T CrB significantly increases in brightness, sometimes becoming visible to the naked eye as a "new star" in the sky.
• Duration:The nova event typically lasts for several days, during which time the star's luminosity rises dramatically.
• Post-Eruption:After the event, T CrB returns to its normal brightness until the next eruption cycle begins.

Observational Details

• Location:Found within the Northern Crown constellation, west of the Hercules constellation.
• Visibility:Observable from the Northern Hemisphere during clear nights, particularly in September when the next eruption is expected.

Nova Explosion

• A nova explosion is a sudden, dramatic increase in the brightness of a star, creating a temporary new star visible in the night sky.
• This phenomenon occurs in binary star systems where one star, typically a white dwarf, accretes material from its companion star, leading to a thermonuclear runaway on the surface of the white dwarf.

Mechanism

• Binary Star System:Consists of a white dwarf (primary star) and a companion star (often a red giant).
• Accretion Process:The white dwarf pulls material from its companion due to gravitational attraction.
• Hydrogen Accumulation:Hydrogen-rich material accumulates on the surface of the white dwarf.
• Thermonuclear Reaction:When enough material accumulates, the pressure and temperature on the white dwarf's surface trigger a runaway fusion reaction of hydrogen into helium.

Characteristics of a Nova Explosion

• Brightness Increase:The star's luminosity can increase by up to 100,000 times its normal brightness.
• Duration:The nova event typically lasts for several days to weeks as the hydrogen is consumed in the fusion reaction.
• Visible Spectra:Novae emit spectra characterized by strong hydrogen lines (Balmer series) due to the hydrogen fusion process.

Difference Between Nova and Supernova

• Nova:Involves a white dwarf star and does not destroy the star. It's a recurring event.
• Supernova:Occurs in massive stars, leading to their destruction in a cataclysmic explosion. It's a one-time event resulting in the formation of a neutron star or black hole.

Sources:

IndianExpress

PRACTICE QUESTION Q: With reference to supernovae, consider the following statements: Type Ia supernovae occur in binary systems where a white dwarf accretes matter from a companion star until it reaches the Chandrasekhar limit, leading to a thermonuclear explosion. Type II supernovae result from the core collapse of massive stars (greater than 8 times the mass of the Sun) after they have exhausted their nuclear fuel. Both Type Ia and Type II supernovae leave behind a neutron star or a black hole as a remnant. Which of the statements given above is/are correct? a) 1 only b) 1 and 2 only c) 2 and 3 only d) 1, 2, and 3 Answer: b)