This is where you’ll find our thoughts about recent (and not) astronomy, earth science and other science news, our answers to questions we get from people a lot, plus whatever else strikes our fancy. Sometimes we get into a few of the mathematical or scientific details, but never too deeply.

Earth's orbital motion around the Sun means that we view different parts of the sky in different months of the year. (Image generated by SkySafari.)

What Stars Are Visible at Different Times of the Year?

As Earth orbits the Sun, the apparent position of the Sun against the background stars changes. As a result, we see different parts of the sky at different times of the year. This annual motion of Earth around the Sun is what gives us our “winter sky” and our “summer sky,” respectively.


Stars are basically giant balls of hydrogen and helium gas, and little else. However, the "little else" matters.

What Are Star Types?

You might have heard that there are different kinds of stars, called stellar types or stellar classes. You might have also heard that these types have cryptic names designated by letters of the alphabet. This post explains what these stellar types are and how they came to be.


Ever falling, ever missing…

That is an orbit.

What Is An Orbit?

In simplest terms, an orbit is the path of a planet around the Sun, or of a satellite around its parent body. The Moon orbiting Earth is an example. But what causes the orbit to have one size and not another? It turns out that all of the properties of an orbit are the result of two physical laws: the law of energy conservation and the law of conservation of angular momentum.


You have probably heard of dark matter- which is different from dark energy - but do you know what it is or why scientists think it exists?

Why Do Astronomers Think There is Dark Matter?

Astronomers often speak of dark matter and dark energy, terms that are confusing for the public and not very descriptive. In brief, both are invisible substances, meaning that they do not interact with any type of light, from radio to gamma-rays, and their existence is only inferred because of the effect they have on the motion of material that we can see. Here we will look at the evidence for dark matter, as well as the ideas scientist have postulated for what it might be. The dark energy will be the subject of another posting.

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