Stars, Galaxies, and Celestial Objects: A Deep Dive

Stars: Celestial Powerhouses

Stars are celestial bodies formed from large amounts of hydrogen and helium atoms. Internal nuclear reactions cause the emission of a large amount of energy. Stars reach very high temperatures and produce fusion reactions that release energy. A fusion reaction involves two hydrogen atoms and one helium atom.

Types of Stars

• Blue-white
• Yellow
• Orange
• Red

Stars are formed from nebulae. They broadcast particles via the Doppler effect. Light and sound propagate as waves. If the issuing body moves, the waves arrive at the receptor more compressed or more elongated as they move away or closer.

Galaxies: Islands of Stars

Galaxies are huge groups of stars, gas, and dust. They have different shapes and sizes, and the number of stars they contain varies.

Types of Galaxies

• Spiral Galaxies: Contain a central bulge and a number of arms. The Milky Way is a spiral galaxy.
• Elliptical Galaxies: Have no arms and are more or less regular. They are formed by old stars and are among the best known.
• Irregular Galaxies: Have no defined shape. Some are classified as dwarf galaxies.

Nebulae: Stellar Nurseries

• Emission Nebulae: Emit electromagnetic radiation. They create new stars.
• Reflection Nebulae: Dust clouds illuminated by nearby stars; they do not emit energy.
• Planetary Nebulae: Clouds of gas and dust expelled by a low-mass star at the end of its cycle.
• Supernovae: Result from the huge explosions of very massive stars.

Other Celestial Objects

• Quasars: Stellar objects that emit a great deal of energy in the form of radio waves.
• Black Holes: Objects from which no radiation can escape due to their enormous gravitational attraction.
• Satellites: Celestial bodies orbiting planets. The most studied satellite is the Moon.
• Asteroids: Objects smaller than planets and satellites that did not aggregate to form a planet.
• Comets: Objects formed by a solid core of water and ammonia. They have very eccentric orbits around the Sun. When they approach the Sun, their temperature increases, and they emit particles of gas.
• Meteorites: Fragments of asteroids, comets, or planets adrift in space. They fall on the surface of planets, and their size varies from a few grams to tons.

The Scientific Method

The scientific method involves identifying the problem, formulating a hypothesis, using a deductive procedure, designing an experiment, and accepting or rejecting the hypothesis.