Writer at The Secrets of the Universe and Founder of Astronomy Hub, I am 17 year old student from Romania. I am an astronomy popularizer and love to teach the subject. I also enjoy classical music and love reading philosophy and literature.
Starting learning astronomy and astrophysics can be tough. Very tough. When you don't have a teacher, it's easy to get lost in the great number of resources you will find over the internet or in books. I've been through that. I can say that there were textbooks in my life that were so good I will never forget, and textbooks that completely blurred me and confused me.
So when starting studying astronomy and astrophysics you may have different goals. You may just be a curious person who wants to learn more as a hobby, and you may be a future scientist in the field and want to start this seriously. I personally encourage both kinds of outcomes. Still, you shouldn't dive deep into astronomy unless you have some background. If you just want to do it as a hobby, reading some popular-science books before is a great solution. For me, pop-science books like "A Brief History of Time" has been decisive in choosing my path in life. They have the advantage of simplifying a lot of important concepts in astronomy or astrophysics, giving a good overview.
Of course, you should try reading some books even if you are aspiring to be a scientist. Among the best there are, I recommend Hawking's "Brief History of Time", "Cosmos" by Carl Sagan, "Astrophysics for people in a hurry" and "Welcome to the Universe" by Neil deGrasse Tyson. The other of Stephen Hawking's books are also a great read, but I will keep another article for discussing popular-science books, and I even plan to launch a series of reviews on more books of this kind.
Now the very important thing for an aspiring scientist in the field of astronomy and astrophysics is the need of physics. You need to master physics before pretending you really understand astronomy and astrophysics. It is one of the mistakes I encountered the most, and one I did myself. Physics is amazing. But driven by the first-sight love you may have for astronomy, it's easy to forget about physics and imagine you can study astronomy without physics. The truth is that the pop science books mentioned above won’t make you professional astrophysicists. For that, you first have to study lot of physics and mathematics.
In the end of the article, I will leave some recommendations of physics textbooks I consider amazing, so check out if you are curious. There are general physics courses, but I suggest from my personal experience and from other's to take a general course first, and then start to dive deep into every of the major chapters of physics.
1. Fundamental Astronomy - Hannu Kartunen, Pekka Kroger
This, in my opinion, is the Bible of astronomy. Covering almost all astronomy and astrophysics branches, and having great explanations and examples, it is one of the best books to start studying astronomy. Also the order of topics is good, and that is a very important thing when starting to study something new. In the first chapter the textbook covers spherical astronomy, which is very important in understanding the basis of astronomy. It then continues with celestial mechanics, to end with cosmology. One thing to remember, cosmology, despite how easy it seems to be from pop-science books, is one of the most difficult subjects of astrophysics. I don't recommend diving into the subject, unless you finished studying all the physics and astrophysics before. Also, if you're not into college, the mathematics is way too hard to understand in high-school.Buy the book here
Overall, as I said, this book is great. I always studied from it and I still consult it when needed.
2. Schaum's Outline on Astronomy - Stacey Palen
Now this is maybe the best book for beginners, who don't want to do all the math and equations to understand something of astronomy. This book is somewhere between popular-science and a real textbook. With the minimum of equations, it covers the major chapters of astronomy and astrophysics and explains the basic concepts: very easy to understand, easy to read.Link to buy the book
3. An Introduction to Modern Astrophysics - Bradley Caroll, Dale Oslie
Many of my friends, which have been to the international Olympiads and have been on the national team (a goal of mine too, hoping will achieve it someday), really believe this is the best textbook there is. It is also my favorite for astrophysics. Of course, it is for advanced studying. Stretching over more than 1300 pages, you can imagine it is not the easiest read. So if you decided to dive deeper in astrophysics, try this. Comprehensive, with no doubt will clarify some things for you.
4. Astrophysical Concepts - Martin Harwit
"Astrophysical Concepts" is amazing I think because it also epxlains and deals with a lot of physics subjects. So even if you are not that familiar with advanced physics, a lot of them are covered. It is about 700 pages long, so it is another book not that easy to study in the conventional way you may be thinking of. Still, it is a great book, well-written, and I studied a great deal of chapters from it and clarified a lot of parts in my training.Link to buy the book
5. Astronomy Principles and Practice - A. E. Roy, D. Clarke
Not one to forget, Roy's book is somewhat of "Fundamental Astronomy". It is a general book, covering all topics, including the basics of astronomy (not to confuse with astrophysics). Not on the level of "Fundamental Astronomy". It is a somewhat more popular textbook. Back when I started studying astronomy, having no teacher, I searched on the internet for the best astronomy textbooks (as some of you may have done too), and more than half of the recommendations were of "Astronomy Principles and Practice". I consider "Fundamental Astronomy" a far better book, but still, Roy's textbook is good. Otherwise I wouldn't have recommended it, right? Indeed, it is good, but honestly the recommendation should be taken more as the people's choice.Link to buy the book
6. An Introduction To Astronomy And Astrophysics - B. Basu
If you want a flavor of astrophysics (not astronomy), then this book is for you. The book beautifully starts with the basic concepts of physics required. It then steadily takes you to the physics and concepts of outer space. This book is a must read to start your journey in Astrophysics. Here is the link to buy the book
7. An Introduction to the Study of Stellar Structure - S. Chandrasekhar
Written by the Nobel Laureate Subrahmanyan Chandrasekhar himself, this book covers advanced stellar astrophysics. Once you have covered basic physics, you may start with this book. Very important for professional astrophysics.Link to buy the book
Honorable Mention. Mathematics of Astronomy - Daniel Fleisch, Julia Kregenow
Now "Mathematics of Astronomy" is a beginner book. Really beginner. But really good if you are not so good with math. It explains the basics for solving basic problems, explains units of measure, and then for each major chapter of astronomy and astrophysics, it explains the basic math and formulas to be able to use the most fundamental concepts in solving some problems. So if you are just starting with astronomy, this is clearly a choice to try.
Something really important to note, a personal advice, would be that you should study one general book, like "Fundamental Astronomy", and whenever you meet new concepts, try to fully understand them by looking up the chapter in some more detailed books. For example, if you are studying binary systems, they are explained perfectly in Kartunen's book, but when looking it up in Oslie you will find a detailed chapter on that. You may even find the same thing, but in a different formulation, which is also good.
Now as I said I will state in short my choices for physics, here I will try to abstain from any further comments.
Choices for some physics topics, worth trying
Mechanics - "An Introduction to Mechanics", Kleppner and "Classical Mechanics", Goldstein
Electricity - "Electricity and Magnetism", E. Purcell
Atomic Physics - "Atomic Physics", Max Born
Quantum Mechanics - "Quantum Physics" by H.C. Verma
And for the best course overall, check Feynman's Lectures.