Stars
Stars are extremely hot, self-luminous celestial bodies very far from Earth; planets are cold and only reflect sunlight. Stars differ in structure and composition. Their colour depends on temperature: bluish-white stars are hottest, yellow stars (like the Sun, surface about 5500 °C) are medium, red stars are coolest. Stars twinkle because their light passes through unsteady layers of air in Earth’s atmosphere. Even the nearest star after the Sun is about 4.2 light-years away; one light-year is the distance light travels in a year (about 9.5 trillion km). The Solar System lies in the Milky Way galaxy. Since ancient times people grouped stars and named the groups – constellations: Ursa Major (the Big Dipper; seven stars shaped like a ladle), Ursa Minor (also seven stars). The Pole Star belongs to Ursa Minor and stays in one place in the sky, above the North Pole.
Model “Constellation”: mark 7 dots in the shape of Ursa Major (the ladle) on black card and open small holes with a pencil tip (not a needle!). In a dark room shine a torch from behind to project the constellation onto the wall and find the Pole Star. If possible observe Ursa Major with adults on a clear night. Safety: do not use sharp needles; make evening observations with parents in a safe place away from roads; never look at the Sun through binoculars.