7.1 Space Flight to the Stars Humans have been studying the sky for millennia. Outer space has fascinated and continues to fascinate people all over the world. Although we have discovered much about space, it remains a mystery to humankind. Gravity Trailer [2013]

Astronomy -Astronomy is the study of the universe and all its objects. This is a very broad range of study. -Some more specific studies pertaining astronomy: cosmology, astrophysics, celestial mechanics, planetary science, etc. -These sub disciplines are studied to give humans a specific look at certain parts of the universe and its properties.

Our Solar System We will discuss our solar system in more detail later in this unit, but here is a brief overview: -A series of planets and celestial objects orbit around the Sun because of the Sun’s gravitational attraction -There are two parts to the solar system: Inner and Outer Solar Systems -Inner Solar System: Mercury, Venus, Earth, Mars -Outer Solar System: Jupiter, Saturn, Uranus, Neptune -We can understand the distances of some of the closer planets, but what about the planets most distant from planet Earth?

Measuring Distances in Space -Planets in the outer solar system are so far away that we cannot fathom the distance in units like metres and kilometres. -For this reason, we use units such as the astronomical unit (AU) -One astronomical unit is equal to the average distance between the Sun and Earth, which is about 150 million kilometres. -Once we get past our solar system, the distance to other celestial objects is so great that we must use larger units. Astronomers use a distance measure called the light-year (ly) So what is a light year?

Light-YearsLight-Years A light year is a unit of distance, not time! There is a reason why it is called a light-year: it is equal to the distance that a beam of light can travel through space in 1 year. It is equivalent to: AU billion kilometres Speed of light= 3 x 10 8 metres/second Think about this: it takes about 8 minutes 20 seconds for light from the Sun to reach Earth, kilometres. THAT IS FAST!!!!!!

To the Stars -Unlike what you might have thought when you were younger, the “Sun” is just another star, and is not by any means a giant intimidating beast to the other stars in our galaxy. The planets of our solar system compared to the Sun Bigger stars compared to the Sun (1 pixel)

To the Stars There are many other solar systems far away from ours. Our closest neighbours are from the Centauri system (4.3 light-years away) -Some systems have more than one star! -Solar system with two stars: Binary system -Eventually, stars explode. They have life spans just as humans do. When a star explodes, it is called a supernova! Some stars can live for millions or even billions of years and suddenly explode in a matter of minutes. This is caused by a gradual buildup of heavy elements in the core of the star.

More stars in space! -After a supernova occurs, new elements form as a result of high pressure and high temperature. Debris from the explosion provides the matter for another celestial object, the nebula. -A nebula is a large cloud of dust and gas. From a nebula, a star can eventually emerge SPACE IS COOL