STARS & NEBULA

The Milky Way and Nebulas

• The Milky Way galaxy is a spiral galaxy that contains numerous regions of gas and dust known as nebulas.

  • Personal favorites include:

    • Horsehead Nebula

    • Cat's Eye Nebula

    • Orion Nebula

The Orion Nebula

• The Orion Nebula is an exceptional nebula to study stellar evolution.

  • Visible to the naked eye, making it easily accessible for observation.

  • Historically significant, referred to as the "fire of creation" by the Maya civilization.

• Represents nearly every stage of a star's life cycle.

  • Strong connection between the life cycles of stars and nebulas.

  • Showcases massive stars nearing death and newly formed stars enveloped in gas.

Visual Features

• Contains intricate structures:

  • Thin gas veils surrounding newborn stars.

  • Pillars of gas colliding.

  • Active regions with stars moving through gas clouds.

• In 2018, NASA developed a groundbreaking 3D visualization of the Orion Nebula's interior, revealing:

  • A cluster of young stars actively disrupting their environment.

  • Solar winds creating clear openings in the gas, allowing for observational insights.

Coloration in the Nebula

• Energetic starlight from the cluster causes the surrounding gas to glow:

  • Pink from hydrogen atoms emitting light.

  • Blue from light of hot new stars reflected off dust.

Types of Nebulas

• Dark Nebula: Dense clouds of dust that block visible light, creating shadowy shapes.

  • Example: Horsehead Nebula, massive enough to potentially form around 30 stars the size of our sun.

• Advancements in infrared technology allow for deep exploration:

  • Infrared light helps in seeing through dust, revealing details inside the nebula.

  • Detectors detect cold regions in dark nebulae, hinting at star formation.

Star Formation Process

• Formation of stars begins with knots of matter gathering under gravity's influence:

  • Increasing mass leads to greater gravitational pull, pulling in more gas.

  • As the mass accumulates, it becomes denser and hotter until fusion ignites.

• Each newly formed star contributes to the galaxy's composition, resulting in countless stars throughout its history.

Cosmological Origins

• Origin of stars and galaxies can be traced back to the Big Bang approximately 13.8 billion years ago:

  • Initial state was pure energy, which cooled to form hydrogen and helium gas.

  • The universe began as a colossal nebula, gradually collapsing and fragmenting into smaller clumps.

Evolution of Stars

• The first stars formed from almost entirely hydrogen:

  • Through fusion processes, heavier elements were created.

• Massive stars burn out quickly, providing complex elements back into the nebula:

  • Each generation of stars contributes to the element pool for future star and planet formation.

Formation of the Milky Way

• The Milky Way formed from a proto galactic nebula that collapsed to create the galaxy.

  • Rich interactions exist between stars and nebulas—a cosmic cycle.

• Our sun is believed to be a third-generation star:

  • It evolved from several cycles of nebula-stellar interactions.

• Formed over 10 billion years, producing elements like carbon, nitrogen, oxygen, and sulfur,

  • Essential for the development of planets and life.

The Role of Supernovae

• Supernovae are violent deaths of stars that release key elements back into the cosmos:

  • Visible across the universe, contributing to the material necessary for life.