Why in News?
Researchers from India's Aryabhatta Research Institute (ARIES) mapped the "skeleton" of magnetic fields in small molecular clouds (L1604 and L121) for the first time. This study revealed how magnetic fields acts as an "invisible hand" that regulates star formation by resisting gravitational collapse.
Composition
- Predominant Gas: Mostly molecular hydrogen (H₂), which is difficult to detect directly because it stays cold and dark.
- Tracers: Astronomers often use carbon monoxide (CO) to find these clouds, as it emits detectable radio waves.
- Dust Grains: About 1% of the mass consists of tiny solid particles (like cigarette smoke) that block visible light, creating "dark nebulae".
Physical Properties
- Extreme Cold: Temperatures typically range from 10 to 30 Kelvin (-263°C to -243°C).
- Immense Mass: Giant Molecular Clouds (GMCs) can reach millions of solar masses and span hundreds of light-years.
- High Density: While still better vacuums than those made on Earth, their cores are dense enough to allow gravity to pull gas together into stars.
The Life Cycle
- Formation: They assemble from atomic hydrogen in the interstellar medium.
- Star Birth: When a cloud's core becomes too heavy or is hit by a shockwave (like a supernova), it collapses to form protostars.
- Destruction: Once massive stars are born, their intense radiation and stellar winds blow the remaining gas away, eventually dispersing the cloud.
Significance
- Foundations of Life: They contain water, alcohols, and amino acids, which can be delivered to new planets via comets and asteroids.
- Galactic Evolution: They are the primary sites where the gas in a galaxy is recycled into new generations of stars.
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