Preface

This course is designed to teach you what you need to know as part of a college-level astronomy course. The study of astronomy has made a great many strides in the last several centuries but certainly, its forward progress is still occurring today. While mankind has always questioned what exists in the skies, we are now exploring these areas in ways that tell us a lot about how the universe was created, what it is made of, and where it is going.

We will talk about the aspects of astronomy that are close to home, such as that of Earth and its single moon. Other planets in the solar system have been extensively studied and are covered in detail in the different chapters of this course. The moons, asteroid belts, and planetoids in the solar system have also been studied so we will talk about what we know about these. The sun is the center of the solar system and is the source of life on earth; for this reason, we will devote a chapter on the sun as well.

Outside of the solar system is the Milky Way Galaxy, other galaxies and planets, and entities we are just beginning to understand, such as black holes. Exploration of these areas lags behind other aspects of astronomy but we will talk about how astronomers are studying these parts of the universe and how, in some cases, they are looking for signs of life outside of planet Earth.

In chapter one of the course, we begin the study of astronomy by looking back at how the skies and the different structures seen in them have been understood and studied from the time of antiquity. Astronomy is probably the world’s oldest field of scientific study as mankind has always held an interest in it. We will talk about the evolution of astronomical theories since ancient times; there was a flood of new information and changing theories about planetary motion and other astronomic details still used today that began to be developed around 1600 CE. These will be covered in this first chapter along with the history of the telescope.

Chapter two focuses on the universe and how it is believed to have started in the first place. Surprisingly, other than creationism, there have been few other theories on the

origin of the universe other than the Big Bang Theory. In this chapter, we will talk about this theory and how the universe has come to evolve into what it is today. There are a few alternate theories about how the universe originated and is evolving, such as the ekpyrotic model of the origin of the universe. We will talk about the theories that exist today and about how we have come to believe in the way our Universe was probably born.

The topic of chapter three in the course is the solar system we live in. We will talk about the solar system in general, including what exists as part of the solar system, how vast it is, and what we consider to be the major and minor planets within it. We will discuss the major asteroid belts in the solar system and how they came to be as well as how planets and other satellites orbit around the Sun. Theories on how old the solar system is and on how it was formed will also be covered in this section.

Chapter four talks about our planet Earth and its only natural satellite, the moon. We will talk about the current theories that exist about how the Earth was formed as well as about the astronomical characteristics of the planet, such as its orbit, size, atmosphere, composition, and magnetosphere. The formation of the moon will also be discussed as well as its known features. We will also take the opportunity to cover the earth-moon system, including the moon’s phases as seen on earth, the phenomenon of tides, and lunar eclipses. Finally, we will discuss solar eclipses as they have been witnessed on this planet.

Chapter five in the course talks about the three terrestrial planets in our solar system other than our own planet Earth. Each of these planets has similar characteristics in that they tend to be solid and rocky. They are also smaller than the larger gas planets further away in the solar system. These planets have origins best explained by the accretion model, where debris in the solar system coalesced and collapsed into a dense sphere through central gravitational forces. We will discuss the features of each planet as we have come to understand them through the modern study of astronomy.

In chapter six, we will study the Jovian planets, which are the furthest from the sun. There are two types, called the gas giants and the ice giants. As you will see, these are fundamentally different planets from the terrestrial planets due to their distance from

the sun, which affects the influence of the solar winds on their formation and current existence. None of these planets is believed to be habitable, mostly because their orbits lie outside the Goldilocks zone in our solar system.

The focus of chapter seven of the course will be the Sun, which is the star around which our solar system rotates. We know the most about stars from studying our own sun. In this chapter, we will talk about how the sun was created and the features we know to be true of the sun, both inside and on the surface. As the sun continues to evolve, we can make some assumptions as to the future of the sun over the time left in our solar system, which will be covered in this chapter as well.

In chapter eight, we will finish up our discussion of the different types of small celestial bodies. We will have already talked about asteroids in the discussion of the asteroid belts in the solar system but here we will discuss comets, meteoroids, and meteorites. We will also talk about Pluto, which is a minor planetary object far beyond Neptune and is part of the Kuiper belt.

In chapter nine in the course, we will go beyond the study of our own star to talk about stars in general. There are many different types of stars and ways to characterize them, which we will talk about. The lifespan of stars has been determined so we will go over this timeline. Supernovas are the fate of some stars. For this reason, this spectacular end to some stars will be discussed in detail in the chapter.

Chapter ten is about what happens at the end of a star’s life. We will have talked about the lifespan of stars and their overall aging process in earlier chapters. In this chapter, we talk about things like neutron stars, pulsars, and black holes, which are really the aftereffects of a star’s death. Black holes are especially intriguing so we will talk about what they are and what it would be like to be near one.

The focus of chapter eleven in the course is galaxies, including what they are, how they form, and the different types there are. Galaxies are incredibly numerous in our vast universe and have a wide range of sizes. We will talk about the different galaxy structures, the contents of most galaxies, and dark matter, which is what the majority of the universe is made from.

In chapter twelve, we will talk about space exploration as it exists today. Mankind has been able to explore space from Earth-based telescopes and from probes and landers sent out beyond our borders. These have been valuable in understanding the universe around us. We will also talk about space travel and the difficulties in doing this, the habitability of planets, and the question as to whether or not it is likely that there is other intelligent life in places other than on earth.