Ch 22: The Sun and it’s Solar System

Topic1: Studying the Sun

            Chinese were the first to observe sunspots, darker, cooler regions on the sun.

Galileo first to use telescopes to record sunspots- He noticed that sunspots move in regular patters.  The sun rotates once every 27 days.

            Solar telescopes are used to study the sun safely.

Topic 2: Properties of the Sun

            The sun’s diameter is 1,380,000 km

            110 times earth’s diameter

            The sun’s volume is over 1 million times that of earth.

            The sun and moon appear to be the same size but the Sun is 400 times farther away.

Topic3: The sun’s Atmosphere

            Only 3 regions of the sun can be studied dirrectily

            Chromosphere

            Photosphere

            Corona

 

III Motion in the Solar System

 

Topic 10: The contribution of Tycho

      Tycho Brahe: Born in Denmark (1546- 1601) made careful observations of stars and planets without any telescopes.  Although telescopes had not been invented yet, he did have many instruments designed for celestial observation.

      His observations and records were made over 20 years and is known for the best ever recored observations before the invention of the telescope and the first long-term sky investigations. 

Topic 11: Johannes Kepler and his 3 laws of Planetary Motion

      Johannes Kepler (1571-1630)

      After Tycho Brahes’ death, Kepler used his notes and observations to develop the famous 3 Laws of Planetary Motion.

      1^st Law: All planets move in elliptical orbits with the sun at on focus.

      aphelion: point in planet’s orbit where it is farthest away from the sun

 

      perihelion: point in planet’s orbit where it is closest to the sun.

 

      2^nd Law: Equal Area Law- The straight line joining the sun and the planet sweeps out equal area in equal intervals of time. 

 

 

 

 

 

 

 

 

      Planets move faster in their orbits when they are closer to the sun.

      3^rd Law: Harmonic Law- The period (P) of a planet squared is equal to the cube of the distance (D) from the sun.

P²=D²

      Period= time it takes a planet to travel one orbit around the sun. 

      This formula is used to find the distance between the sun and a planet if the period is known or the period of a planet if the distance is known. 

Topic 12 Galileo and the Telescope

      Galileo 1^st astronomer to use telescope to observe stars, moon and planets.

      Made very careful observations of the moon (craters)

      Observed the phases of Venus.  Venus goes through phases just like our moon.

      Observed the 4 major moons of Jupiter (this gave evidence of the “heliocentric theory” – all objects do not go around the earth which is what was previously accepted (geocentric theory)

Topic 13 Isaac Newton

      Universal Law of Gravitation

      Force of gravity between two objects (planes) directly related to masses but inversely related to the masses but inversely related to square of the distance between the objects.