Life Cycle of a Star

Context:

James Webb Space Telescope (JWST) captures stunning images of a forming star.

Key findings:

• NASA and the European Space Agency (ESA) released composite images captured by JWST.
• Images show a plume of gas and dust streaming from a forming star.
• The star-forming region is located about 625 light-years from Earth.
• This region is one of the closest star-forming areas within the Milky Way galaxy.

About JWST

• JWST is considered the successor to the Hubble Space Telescope.
• It is an advanced space-based observatory launched in 2021.
• JWST primarily studies the universe in the infrared spectrum.

Life Cycle of a Star:

Nebula (Birth):

• A star begins as a nebula, a large cloud of gas (hydrogen, helium) and dust.

Protostar:

• Gravity causes the nebula to collapse into dense, heated, and spinning regions.
• These regions form a protostellar disk.

Main Sequence:

• The longest phase of a star, where it fuses hydrogen into helium in its core.
• Example: The Sun is about halfway through its main sequence.

Red Giant or Supergiant (Based on Mass):

• When core hydrogen is depleted, the star evolves differently based on its mass.
  • Low to Medium Mass Stars (e.g., the Sun):
    • Core contracts while outer layers expand, forming a red giant.
  • Massive Stars:
    • Expand into supergiants, fusing heavier elements like carbon, oxygen, and up to iron.

End Stage:

• Low to Medium Mass Stars:
  • Outer layers are ejected as a planetary nebula.
  • The core becomes a dense, non-fusing white dwarf.
  • If core mass remains below the Chandrasekhar Limit (1.4 solar masses), it stays stable.
• High Mass Stars (10 solar masses or more):
  • Core accumulates iron, collapses under gravity, and rebounds in a supernova explosion.
  • If remnant core mass is:
    • 1.4–3 solar masses: It forms a dense neutron star.
    • More than ~3 solar masses: It collapses into a black hole, with gravity so strong that light cannot escape.

Source: The Hindu

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Previous Year Question

The terms ‘Event Horizon’, ‘Singularity’, ‘String Theory’ and ‘Standard Model’ are sometimes seen in the news in the context of

[UPSC Civil Services Exam – 2017 Prelims]

(a) Observation and understanding of the Universe
(b) Study of the solar and the lunar eclipses
(c) Placing satellites in the orbit of the Earth
(d) Origin and evolution of living organisms on the Earth

Answer: (a)

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