The Sun, Our Star


The sun is a lot larger than people think. When we see it in the sky, it looks small (as big as our Moon looks, in fact). However, it only looks this small because of how far away it is. The radius of the sun is 690 million meters—109 times the size of the Earth. To put that into perspective, if the sun were a balloon blown up to about one foot across, the earth would be the size of a peppercorn. It makes one think, “Well what about the largest planet in our Solar System?” At that scale, Jupiter would be about the size of an unshelled walnut. Yeah, the sun is huge. It’s also massive. The total mass of the sun is roughly the mass of 300,000 Earths. Plus, it’s also extremely bright. The sun’s luminosity is 1025 times brighter than a 40-Watt lightbulb. That’s 25 zeros after the 40. We don’t even have word for a number as big as that.

So yeah, the sun: super big, super massive, super bright.

“Isn’t our sun gonna [sic] blow up one day?” As an educator of physics and astronomy, I get asked this question a lot. The short answer is well, yes and no. Yes, it will blow up into planetary nebula billions of years from now, but usually people are referring to the event that will happen in 5 billion years. In 5 billion years, our sun will grow so old that it will begin swelling up into a red giant. Right now, our sun is a yellow, G-Type Main Sequence star. This classification is based on the Hertzsprung-Russell diagram used to classify stars based on their brightness and temperature. If you ever took Earth Science in high school, or astronomy in college, your paths may have crossed. Red giants are, as the name says, red; they are a bit cooler, but a bit brighter than our current sun. There are a lot of giants and super giants in the universe, but the one that comes to mind is Betelgeuse—it’s pronounced just like the 1988 movie, Beetlejuice. Betelgeuse is a super-giant star in the constellation Orion. Orion’s Belt is the most common constellation people usually point out in the sky when they see it. Orion’s Belt is the three stars in a row that we see in the winter skies (at least in the Northern Hemisphere.) Our sun won’t be as big as Betelgeuse one day, but it will swell up to a size big enough to engulf the first two planets of the Solar System and reach the Earth.

Either way, the Earth will be way too hot to live on without some advanced technology to aid us. Even more of a reason to expand our space exploration budget!

After our sun becomes a red giant, it will stay that way for a long time. Eventually, our star will run out of hydrogen and begin burning other heavier elements, leading all the way up to iron. The interesting thing about this is that when a star begins to fuse iron, it is doomed. Unlike the other elements, which release energy when fusing, iron absorbs energy when it fuses. Until then, the outward push of fusion counteracts the inward pull of gravity on the star. All the sucked-up energy eventually causes the sun to not be able to fight the pull of gravity. Thus, it collapses in a catastrophic implosion, releasing a huge amount of energy, resulting in a beautiful planetary nebula.

Planetary Nebula

People sometimes think planetary nebulas and supernovae (plural of supernova) are the same. There is a difference between them. A supernova occurs when a star, much bigger than our sun, explodes. This causes a much bigger explosion than a planetary nebula, leaving behind a supernova remnant and a tiny neutron star. This neutron star is about the size of the island of Manhattan.

There are a lot of pictures of planetary nebulae and supernovae on Some of my favorites are the Cat’s Eye Nebula, the Eskimo Nebula, and the Supernova Remnant Cassiopeia A. All that will be left of our sun will be a tiny white dwarf. Our sun will end up hotter but dimmer than it is now, and about the size of the Earth. It boggles my mind to think that something so huge can end up as something so small.

Cat’s Eye Nebula
Eskimo Nebula
Supernova Remnant Cassiopeia A

To think… currently, we can fit about 100 Earths across the sun, and one day, it will be the size of our planet. Hopefully, we’ll be long gone from the Earth when that happens. Hopefully.

I’ve heard people get confused between lunar and solar eclipses—which is which? Lunar comes from the Latin word for moon—luna. Solar comes from the Latin word for sun—sol. Luckily, many languages already use luna and sol, so many already know this! From there, the phases just translate from lunar eclipse and solar eclipse as moon eclipse and sun eclipse, respectively. Thus, this summer the solar eclipse will be the sun undergoing an eclipse—it will be blocked from our view.

Lunar Eclipse

How does that happen? Most elementary school students can tell you that the moon passes in front of the sun and blocks the light out. Usually, people stop their thinking there. However, many continue to ponder this idea and formulate questions—many of these people are my own students. There is so much more beauty to solar eclipses.

When a solar eclipse occurs and you happen to be in an area where you can see the moon completely cover up the sun, we call this totality. Only with totality, one can see a beautiful halo of light appear around the immensely dark moon. We call this halo the “corona.” Here’s what makes the corona so special: not only does it happen when the moon completely covers the sun, but also because the moon appears to be the same size as the sun appears in the sky! It is absolutely mind boggling to think that coronas would not exist if the moon were just a little farther away from us, or a little closer.

Solar Eclipse

In fact, the moon was closer to us many years ago. By many, I mean millions. The moon was formed during a period called “The Heavy Bombardment,” when a large rock collided with the Earth, causing a piece of the Earth to separate and begin orbiting around the remaining large mass. This piece is what we now know as the moon. As the years went on, the moon was in a relatively stable orbit—relatively stable because it was (and still is) drifting away from us.

Thus, the dinosaurs experienced solar eclipses, but because the moon was so much closer than it is today, they never saw the beauty of the corona. Millions of years from now, our moon will have drifted so far from us that when it does move in front of the sun, it will be too small to cover up the entirety of it. Once that happens, we will never have another eclipse on Earth.

Luna, our moon, is a beauty. Our sun gives us life. Working together, the moon reflects light from the sun, giving us romantic moonlit nights on Earth. Our sun and moon are not unique, because there are many moons and many stars in our galaxy alone. Nonetheless, we learn a great deal from the two of them, and we can’t help but feel that they are special to us.


There are Millions possibly Billions of Star planet moon triokas. The biggest question is not if there are eclipses that give someone the solar or lunar eclipse that we so often view? It is are their intellegent beings standing on that planet that can view and enjoy the wonderful beaty of what we see all to seldom. dray