Solar System

Posted on Dec 5, 2024 in Physics

Solar System: A Celestial Overview

The solar system encompasses celestial bodies extending 6,000 million kilometers from the sun. It includes:

  • 1 star (the sun)
  • 8 planets
  • Dwarf planets
  • Natural satellites
  • Asteroids
  • Comets
  • Meteorites
  • Vast quantities of gas and dust

Planets

  • In ancient Greek, meaning “wandering star”
  • Cold surfaces in thermal equilibrium with solar radiation
  • Shine by reflecting sunlight; they do not generate their own light
  • Small and rocky (closer to the sun)
  • Large and gaseous (further from the sun)
  • The asteroid belt lies between these two groups

Ptolemy

(137 AD) devised a geocentric model to explain planetary motion: a stationary Earth with the sun, moon, and planets orbiting in circular paths. Stars were positioned beyond.

This model persisted until Nicolaus Copernicus (1473-1543) proposed a heliocentric system, placing the sun at the center with Earth and other planets orbiting it. This simplified our understanding of the solar system.

What is the Universe?

Stars

Stars are masses of gas, primarily hydrogen and helium. Internal reactions continuously release energy, emitted as light and heat.

Main Properties:

  • Brightness: Light received from Earth, depending on the star’s luminosity and distance.
  • Color: Related to temperature (25,000–3,500 °C). Stars can be blue, white, yellow, orange, and red (in descending order of temperature). The sun is a yellow star.
  • Size: Compared to the sun:
Supergiants:

130–400 times larger than the sun.

Giants:

16–60 times larger than the sun.

Medium:

Virtually the same size as the sun.

Dwarf:

Smaller than the sun.

Nebulae

Gigantic dust and gas clusters that do not emit their own light. They absorb and reflect light from nearby stars. Some form from exploding stars (novas), others from star-forming material.

Galaxies

Huge clusters of stars, dust, and gas. Through a telescope, they appear as diffuse stains of varying shapes.

Planets

Celestial bodies that do not emit light and orbit a star (translation). The further a planet is from its star, the longer its orbital period.

Natural Satellites

Celestial bodies that do not emit light. They orbit a more massive planet, exhibiting both translation and rotation.

Comets

Small, rocky bodies with highly elliptical orbits around a star. They typically have a central core (methane, helium, and ammonia), a gaseous atmosphere (coma), and a tail. The tail lengthens as the comet approaches the star.

Asteroids

Rocky bodies smaller than planets, orbiting a star. They have various shapes, some spherical, others irregular.

Meteorites

Solid matter smaller than asteroids, orbiting a star. They can fall onto a planet’s surface due to gravitational pull.

The Sun

A star composed of incandescent gases (hydrogen and helium). It produces immense energy, providing light and heat to our planet. It is approximately 4.65 billion years old, contains over 99% of the solar system’s mass, and exerts strong gravitational influence on other planets. It rotates and translates.

Solar System Planets

Mercury

The smallest and closest planet to the sun. It lacks an atmosphere and has many craters from meteorite impacts.

Venus

Has a dense atmosphere of CO2 and SO2. Shows lava plains and volcanoes. Presents craters.

Earth

An oxygen-rich atmosphere essential for life. Much of its surface is covered by water (“blue planet”), and it is the only planet with conditions suitable for life.

Mars

A thin atmosphere of CO2 and small polar ice caps. Evidence suggests the presence of liquid water in the past.

Jupiter

The largest and most massive gas giant. It has a banded atmosphere of hydrogen, helium, ammonia, and methane. It possesses rings.

Saturn

A gaseous planet, second largest, characterized by prominent rings. Its atmosphere consists of hydrogen, helium, and methane.

Uranus

A gaseous planet with rings. Its atmosphere contains helium, hydrogen, methane, and other hydrocarbons. Methane absorbs red light, giving it a greenish-blue appearance.

Neptune

The furthest planet from the sun. Its atmosphere (methane, ammonia, hydrogen, and helium) has temperatures near -260°C, resulting in frozen methane clouds. It also has rings.