For the second time this month we have a full moon this week, and when that happens the second full moon of the month is traditionally called a “blue moon.”

They don’t happen that often because it’s tough to get two full moons in a given month. That’s simply because full moons occur every 29.5 days, and with a typical calendar month containing 30 to 31 days it’s not hard to see why blue moons don’t happen that often.

That’s basically the origin of the term “once in a blue moon.” On average we get a blue moon every two and a half years.

What’s really unusual is that this is our second blue moon in 2018. That only happens four to five times a century.

As nice as full moons are to gaze at, they really wash out the Butler sky with light and make serious or even casual star gazing tough. So this week I’d like to go back to the basics and try to answer the age-old question, “twinkle, twinkle, little star, how I wonder what you are?”

First of all, stars are anything but little. Those “little” lights adorning the night sky are all big balls of gas, some much bigger than others. Even the smallest shiners we gaze upon are much bigger than our home planet. Stars are basically huge balls of mainly hydrogen gas with incredible nuclear fusion furnaces deep within, near their cores.

The closest star to Earth is our sun, a little over 93 million miles away. That’s celestial chicken feed, though, compared with the rest of the stars that show themselves after our sun is down.

The next closest star to the Earth is almost 25 trillion miles away. That’s a 25 with 12 zeros after it. That works out to be 4.3 light years away, with just one light-year equaling 5.8 trillion miles, or the distance that a beam of light travels in one year’s time.

Most stars that you see at a glance in the sky are much farther, some of them hundreds, even thousands of light years away.

No matter how far away, all stars are about the same and are similar to our own sun, whether they are in our own Milky Way galaxy or one of the billions and billions of other galaxies in our universe that stretches out to God knows where.

In fact, at least in our home Milky Way, the sun is considered by most astronomers to be of average size and mass. It’s 864,000 miles in diameter, compared to our less than 8,000-mile wide Earth.

More importantly, the sun is a heck of a lot more massive than our Earth. How does 300,000 times more massive than our world grab you? I know it’s hard to believe that a ball of gas can be that heavy, but it truly is.

OK, so the sun is a big ball of mainly hydrogen gas. What makes it shine? Why is the temperature of its surface more than 10,000 degrees?

As I said before, the sun and the other stars have nuclear fusion furnaces inside of them, but what fuels that furnace? The answer is simple. It’s gravity. The same force that makes your skin sag as you get older is ultimately fueling the sun and other stars.

Because the mass of the sun is so large, the gravitational field around it is so strong that not only do the planets in our solar system obediently orbit it, but our sun is being squeezed by its own gravity.

It’s estimated that this gravitational squeezing of our sun increases the pressure inside like crazy, to the tune of more than 500 billion pounds per square inch toward the center. In turn, that drives up the temperature at the sun’s core to an estimated 27 million degrees. That tremendous heat is the trigger for the nuclear fusion furnace.

Nuclear fusion is a tremendously complicated process, but the essence is this. Hydrogen atoms at the core of the sun are moving very fast because of the tremendous heat, forcing tremendous collisions between them.

These collisions are so violent that the hydrogen atoms fuse together, creating heavier helium atoms. In the process, energy is produced that finds its way to the sun’s surface. By the time this radiation reaches the visible surface of the sun it’s cooled off to a little over 10,000 degrees.

Now there’s a little more to it, but I know the Butler Eagle wants to have other things in its paper today than just this column. The gist of it is that gravity is the trigger; hydrogen is the fuel of the sun, or any other star for that matter; helium is the ash; and energy is the byproduct.

Now what about the twinkling of those not so little stars? Actually that has nothing to do with the stars themselves, but rather our turbulent atmosphere jerking around the light waves from these far away stars.

The higher the winds are in all levels of the atmosphere, the more the stars will twinkle. That’s why amateur astronomers like to observe with their telescopes on calm, clear evenings. The images through telescopes of any size are clearer, and you don’t have to deal with the wind chill/

Make the stars your old friends

If you have any astronomical questions or want me to write about something you’re seeing in the night sky drop me a line at mikewlynch@comcast.net.

Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St. Paul. He is also the author of “Stars: a Month by Month Tour of the Constellations,” published by Adventure Publications and available at bookstores and at adventurepublications.net. Contact Mike Lynch at mikewlynch@comcast.net.