Astronomy Basics

Until the middle of the 20th century, it was not entirely clear that the Universe even had a beginning. Now, scientists are trying to solve the mysteries of the early Universe. While there are certainly multiple theories out there, the leading explanation on how the Universe came into existence is known as the Big Bang theory. However, there are...

Astronomy, derived from the Greek words for star law, is the scientific study of all objects beyond our world, and the process by which we seek to understand the physical laws and origins of our universe.

A comparison of the terms astronomy, astrophysics and astrology. Often confused, the differences and similarities are analyzed and discussed.

Johannes Kepler (1571-1630) was a German astronomer and mathematician. After Tycho Brahe (1546-1601) settled in Prague in 1599 (then the site of the court of the German emperor Rudolf) and became court astronomer, he hired Johannes Kepler to carry out h…

planetology - from an ever growing glossary of space and astronomy definitions. Find the definitions for planetology and all your space and astronomy related words in this online dictionary - glossary.

Although many earlier philosophers had theorized that the Earth was not the center of the universe, it wasn't until the publication of Nicolaus Copernicus' "De Revolutionibus Orbium Coelestium" (On the Revolutions of the Celestial Spheres) that the Heliocentric model of the universe took shape.

What Would Happen If The Sun Was Gone? Frequently Asked Questions About Space - Basics Series; What You Need To Know About Space. Discover the answers to some frequently asked questions about space.

Here is a free ten lesson basic astronomy course. Learn a little about the history of astronomy as well as our universe and how to view the night sky. Earn your certificate.

"Visual magnitude" is a scale used by astronomers to measure the brightness of a star. The term "visual" means the brightness is being measured in the visible part of the spectrum, the part you can see with your eye (usually around 5500 angstroms).

Solar means dealing with the sun, Sol. Our sun is just a star, the closest one to Planet Earth. The Solar System is everything that centers around the sun. That includes 8 planets as well as some smaller objects such as asteroids, comets and meteoroids.

There has been a considerable crescendo in the debate over whether a tiny orb in the outer reaches of the solar system should or should not be considered a planet. Both sides make valid arguments, while others argue that it doesn't even really matter. So where do we go from here?

When we think of stars we usually imagine our Sun. But the simple fact is that the Universe is made up of many different types of stars. In fact looking into the heavens most stars look very different, and some aren't really stars at all. So here is a run down of the most common types of stars in the galaxy.

Everything that contains "hot" matter - basically anything with a temperature - is going to emit electromagnetic radiation. Formally this emission is termed thermal radiation.

Matter is all around us, it is the physical material of the Universe. But there is more to matter than just mass.

The Universe is immense by any measure, but it wasn't until 1929 when Edwin Hubble realized that the Universe extended beyond our own galaxy that we truly began to understand the scale of the expanse.

For more than 200 years Newton's laws of gravity and motion were the gold standard of physics. But there was a problem, large scale dynamics, like those observed in astronomy, did not fit within the Newtonian framework. Then, in the early 1900s a new theory was born, a theory which posited that space and time were relative quantities. So what...

In 1905 Albert Einstein first published his theory of special relativity. But it was incomplete, it only considered objects moving in constant, uniform motion. To answer the question of what happened when objects accelerated, something more was needed. From this was born Einstein's theory of general relativity.

For two hundred years the laws of motion were governed by equations derived by Isaac Newton. Then in 1905, Albert Einstein developed a new theory of motion, one that described space and time as relative quantities, and the theory of special relativity was born.

One of the revelations of Albert Einstein's theory of relativity was that the speed of light in a vacuum was a constant. Furthermore, it set the limit for the greatest speed anything could travel. But what is the speed of light?