Solar System Development and Observational Astronomy

Development of the Solar System

• Nebular Theory:
• Starts with a nebula (cloud of gas and dust).
• Nebula collapses due to gravity and begins to spin, flattening into a protoplanetary disk.
• Most material forms a protostar (future Sun).
• Dust and gas coalesce into planetesimals, forming planets.
• The Sun activates and clears leftover gas with solar wind.

Crater Counting:

• A method for determining surface age.
• More craters indicate an older surface, while fewer craters indicate a younger surface.

Formation of Terrestrial vs. Jovian Planets:

• Terrestrial Planets (Mercury, Venus, Earth, Mars):
• Formed close to the Sun, from rocks and metals.
• Have solid surfaces and thin atmospheres.
• Jovian Planets (Jupiter, Saturn, Uranus, Neptune):
• Formed farther from the Sun, from gases and ices.
• Have no solid surfaces but thick atmospheres and many moons/rings.

Celestial Coordinates (RA & Dec):

• Right Ascension (RA): Equivalent to longitude; position east/west of the vernal equinox.
• Declination (Dec): Equivalent to latitude; position north/south of the celestial equator.
• Pros: Fixed system; great for long-term observation.
• Cons: Abstract and hard to visualize.

Eclipses:

• Solar Eclipse: Moon blocks Sun's light (Sun → Moon → Earth, occurs during new moon).
• Lunar Eclipse: Earth blocks sunlight to Moon (Sun → Earth → Moon, occurs during full moon).
• Eclipses only occur when orbits align properly.

Moon Formation (Giant Impact Theory):

• Mars-sized object (Theia) collided with Earth, forming the Moon from debris.

Types of Telescopes:

• Ground-Based Telescopes: Cheaper, larger sizes possible, but images are blurry.
• Space-Based Telescopes: Clear images unaffected by atmosphere but are expensive and smaller.

Sun's Interior Structure:

• Core: Nuclear fusion; temp ~15 million °C.
• Radiative Zone: Energy moves outward slowly.
• Convective Zone: Hot gases rise and sink.
• Photosphere: Visible surface; where light escapes.
• Chromosphere: Thin red layer, visible during eclipses.
• Corona: Outer atmosphere, visible during total solar eclipses, very hot.