Lesson 7: Discoveries about our Solar System

NATs 1745: History of Astronomy Lesson 7: Discoveries about our Solar System The Telescopes of William Herschel: ● ● William Herschel significantly advanced the field of astronomy with his innovative telescopes. Herschel's designs allowed for unprecedented clarity and depth in observing celestial objects. He constructed the largest and most powerful telescopes of his time, which enabled the discovery of Uranus, its moons, and numerous deep-sky objects such as nebulae and star clusters. His contributions laid the groundwork for modern observational astronomy. The Discovery of Planet Uranus: Before Uranus was discovered, the known solar system consisted of six planets. On March 13, 1781, William Herschel observed a new object that he initially thought was a comet but later identified as a planet, Uranus. This discovery expanded the known boundaries of the solar system and challenged existing astronomical models. ● Uranus’s discovery was pivotal because it was the first planet found with a telescope, highlighting the importance of technological advancements in astronomy. Features of Uranus, Deity of the Sky: - Named after the Greek deity of the sky, Uranus is unique in several ways: ● ● ● Physical Characteristics: Uranus has a blue-green color due to methane in its atmosphere. It is the third-largest planet by diameter. Axial Tilt: Uranus has an extreme axial tilt of about 98 degrees, causing it to rotate on its side. This leads to unusual seasonal variations. Moons and Rings: Uranus has 27 known moons and a faint ring system, which were discovered through subsequent observations after Herschel’s initial findings. Bode’s Law and a Planetary Puzzle ● Bode’s Law, formulated in the 18th century, suggested a mathematical pattern in the distances of planets from the Sun. ● The law predicted the existence of a planet between Mars and Jupiter. The search for this missing planet led to the discovery of the asteroid belt. **While not entirely accurate, Bode’s Law influenced the direction of astronomical research and the eventual understanding of planetary formation.** NATs 1745: History of Astronomy The 'Celestial Police' and the Discovery of the Asteroid Belt: - In response to Bode’s Law, a group of astronomers known as the "Celestial Police" searched for the predicted planet. HENCE, this led to the discovery of the first asteroids: Ceres, Pallas, Juno, and Vesta. These findings revealed the existence of the asteroid belt, a region of space populated by numerous small bodies. - The discovery of the asteroid belt provided crucial insights into the early solar system and the processes that shaped its formation. The Discovery of Planet Neptune: The Hypothesis: ● Discrepancies in Uranus's motion suggested another planet's influence. ● Two mathematicians, Urbain Le Verrier in France and John Couch Adams in ● England which independently calculated the possible position of this mystery planet. The Discovery: ● In 1846, Johann Galle at the Berlin Observatory, using Le Verrier's calculations, pointed his telescope to the predicted spot. ● There, Neptune was observed almost exactly where the math had indicated, confirming the planet's existence. Significance: ● This discovery not only added another giant planet to our solar system but also showcased the incredible predictive power of mathematical astronomy. ● It marked a pivotal moment in the history of astronomy, where theoretical calculations led directly to observational discoveries. The Nebular Hypothesis and the Origin of the Solar System The Nebular Hypothesis, proposed by Pierre-Simon Laplace in the 18th century, suggests that the solar system formed from a rotating cloud of gas and dust. - This hypothesis explains the formation of the Sun, planets, and other solar system bodies through processes of accretion and condensation. It remains a fundamental theory in understanding planetary formation and the evolution of the solar system. Giants vs. Terrestrials: NATs 1745: History of Astronomy The solar system consists of two main types of planets: ● ● ● Gas Giants (Jovian Planets): Jupiter, Saturn, Uranus, and Neptune. These planets are large, have thick atmospheres primarily composed of hydrogen and helium, and possess multiple moons and ring systems. Terrestrial Planets: Mercury, Venus, Earth, and Mars. These are smaller, rocky planets with solid surfaces and thinner atmospheres.