Chapter 9.1: Earth in Space The Night Sky Chapter 9.1: Earth in Space

Questions to think about… Why do we have seasons? Why does the Sun rise in the East and set in the West? Why is there sometimes a full moon and other times none at all? What is a constellation? What is a star sign? Why is Pluto no longer considered a planet?

Stars Are massive burning balls of hydrogen gas. Light and heat produced from a star is a result of nuclear fusion – Hydrogen coverts to Helium. Releases HUGE amounts of energy as heat, light and radiation. Nearest star to Earth = the Sun! (1,500,000 km away). Takes 8 minutes for heat/light from the sun to reach us!

The Milky Way Is a white band of light formed from more than 200 billion stars. (appears as a band of light that runs across the night sky from one horizon to the next). Only a few thousand of these stars can be made out distinctly, and of these, only a few are bright enough to be named.

Constellations A group of stars that forms a recognizable pattern when viewed from Earth. Location dependent Culture dependent Eg, The Southern Cross , Orions’ Belt The most famous constellations in the Western World = the signs of the Zodiac.

Orion’s Belt

Southern Cross

The Zodiac The 12 constellations that make up the Zodiac are considered special as they are the only constellations that the Sun passes through. Each Zodiac is visually apparent at different times of the year, hence the dates associated with each ‘star-sign’ These dates were originally assigned by the ancient Greco-Egyptian astronomer – Claudius Ptolemy

The Zodiac

Astrology vs. Astronomy The belief that the positions of the Sun, stars and planets affect a person’s personality and the day-to-day events of their life. No scientific evidence that backs this up. The Scientific study of planets, stars and other objects in the night sky. Theories and models must be supported by evidence. FOCUS of chapter!

Planets – The ‘8’ No nuclear explosions, like stars. Only reflect light falling on them from the Sun – how we see them! Rocky planets – terrestrial: Mercury, Venus, Earth, Mars Mercury/Venus = morning/evening stars – visible at dawn/dusk The Gas Giants – balls of gas with a small, rocky core – Jupiter, Saturn, Uranus, Neptune

The Planets…

Dwarf Planets Roughly spherical and travel around the Sun. Do not have enough mass to clear surroundings of dust/rocks. Pluto is now considered a dwarf planet. Other examples include Makemake, Hi’aka, Namaka, Charon, Hydra, Nix, Dysnomia, Eris. Other dwarf planets are located beyond Pluto in a region of icy rock fragments called the Kuiper Belt.

The Dwarf Planets…