Filaments

WHY IN NEWS ?

• On December 3, researchers from the University of Oxford reported:
  • Discovery of a ~50 million light-year-long galaxy filament.
  • The filament shows aligned galaxy spins, suggesting that the entire filament itself is rotating.
• The team claims it may be:
  • “One of the largest spinning structures ever observed in the universe.”
• This provides direct observational support to predictions made by cosmological simulations.

Relevance :

GS Paper III – Science & Technology

• Astrophysics and cosmology
• Dark matter and large-scale structure of the universe
• Observational astronomy and simulation-based science

GS Paper I – Physical Geography (World Geography Interface)

• Large-scale structure of the universe
• Formation of galaxies and cosmic web

WHAT ARE COSMIC / GALAXY FILAMENTS?

• Cosmic filaments are:
  • The largest known structures in the universe.
  • Thread-like formations forming the Cosmic Web.
• They are composed of:
  • Dark matter
  • Intergalactic gas
  • Galaxies
• Typical scale:
  • Tens to hundreds of millions of light-years
• They:
  • Connect massive galaxy clusters
  • Surround vast empty regions called voids

STRUCTURE OF THE COSMIC WEB

The large-scale universe is arranged into:

• Filaments → long, thread-like galaxy highways
• Walls/Sheets → flat, dense galaxy regions
• Nodes (Clusters) → intersections of filaments
• Voids → enormous empty regions
• Together, these form the Cosmic Web, the universe’s fundamental large-scale architecture.

HOW DO COSMIC FILAMENTS FORM?

• Originates from:
  • Tiny density fluctuations just after the Big Bang
• Under the influence of gravity:
  • Matter collapses into sheets
  • Sheets intersect → filaments
  • Filaments intersect → clusters
• Dominant driver:
  • Dark Matter, which provides gravitational scaffolding
• Ordinary matter (gas + galaxies) follows dark matter distribution.

WHY ARE FILAMENTS CALLED “COSMIC HIGHWAYS”?

• Gas and small galaxies:
  • Flow along filaments toward massive galaxy clusters.
• This inflow:
  • Feeds galaxy growth
  • Triggers star formation
  • Shapes galactic evolution over billions of years
• Hence, filaments decide:
  • Where galaxies form
  • How fast they grow
  • How much fresh gas they receive

HOW DO ASTRONOMERS DETECT FILAMENTS?

• By:
  • Mapping positions and distances of thousands of galaxies
  • Using redshift surveys
• Then:
  • Tracing spatial clustering patterns
• Supported by:
  • Large-scale computer simulations based on:
    • Lambda-CDM Model of cosmology
• These simulations reproduce:
  • Filaments, walls, voids, and clusters almost exactly as observed.

WHAT EXACTLY DID THE OXFORD TEAM DISCOVER?

• A ~50 million light-year galaxy filament
• Traced by:
  • At least 14 galaxies
• Unique feature:
  • The galaxies’ axes of rotation are aligned with the filament’s direction
• Interpretation:
  • The entire filament is slowly rotating as a coherent structure

WHY IS ROTATION OF A FILAMENT IMPORTANT?

• Earlier belief:
  • Filaments are static gravitational channels
• New result shows:
  • Filaments can have large-scale angular momentum
• This supports:
  • The theory that gravitational infall and tidal forces can spin up even gigantic cosmic structures
• It links:
  • Galaxy-scale rotation → filament-scale rotation → cosmic-scale dynamics

SCIENTIFIC SIGNIFICANCE

• Confirms that:
  • Angular momentum exists at the largest observable scales
• Strengthens:
  • Theoretical predictions from cosmological simulations
• Helps explain:
  • Why galaxies in the same filament often show spin alignment
• Improves understanding of:
  • Structure formation
  • Galaxy evolution
  • Dark matter dynamics

IMPLICATIONS FOR COSMOLOGY

• Validates:
  • The gravitational instability model of structure formation
• Improves:
  • Precision in large-scale universe mapping
• Supports:
  • The idea that:
    • The universe evolved from tiny early ripples into a connected cosmic network

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