The Eight Planets of Our Solar System

Solar System

Yes. That is correct. Eight planets. Not nine, since Pluto was decommissioned and reduced to a planet dwarf planet in 2006 that is part of the Kuiper Belt. An area at the edge of the solar system that is filled with icy bodies that orbit the sun.

A dwarf planet is an object that revolves around the sun but is not considered a planet because it doesn’t meet the criteria set forth by the International Astronomical Union (IAU), an international organization that helps to set the standard for outer space quantifications.

Want to learn more about the dwarf planet, Pluto, check it out here.

The Eight Planets


The planet Mercury is mainly composed of the element iron. It is one of the few planets that have no moons and there is a good reason. Being so close to the Sun, the gravitational pull would grab those moons like a magnet, and they consequently would be incinerated.

Planet Mecury
The planet Mercury is seen in silhouette, the lower third of the image, as it transits across the face of the sun Monday, May 9, 2016, as viewed from Boyertown, Pennsylvania. Photo Credit: (NASA/Bill Ingalls)

Designated as the smallest planet in our solar system, Mercury is the closest planet to the sun. Only 36 million miles or 0.39 AU (astronomical unit. The distance from Earth to the sun has an AU of 1).

It orbits the sun every 88 Earth days. (The closer the planet is to the Sun, the faster it revolves around it) and it passes between Earth and the sun only about 13 times a century. The last pass was in 2006.

Mercury has a thin atmosphere. We humans as well as all air-breathing mammals on this planet would not survive in Mercury’s atmosphere without protective equipment, but it is unlikely you would want to go there anyway when the average temperature is 354 degrees F. In 1974, two spacecraft visited Mercury: Mariner 10 and Messenger. Learn More about Mariner.


Planet Venus
Image Credit: NASA/JPL-Caltech

The second planet from the sun and slightly smaller than Earth, it revolves around the sun every 225 Earth days. Over 40 spacecraft have explored Venus. Notably, Magellan mapped over 98% of the planet’s surface. Venus’ temperatures can go up to 480 degrees. The planet is unusual as it spins backward, resulting in the sun rising in the west and setting in the east.


NASA Photo of the Earth
Photo by Pexels

Where would we be without it? Our planet is located in the Goldilocks Zone. The name was coined from the Three Bears children’s story. We are situated in the area of the solar system where it is not too hot, not too cold, but just right for life as we know it to exist and strive.

With that said, scientists are currently looking at exoplanets (planets outside of our solar system)  that also are in the Goldilocks Zone. 15% of all stars in our galaxy have planets orbiting around them and if you add them together, it would total over 500 habitable planets that have been discovered so far, so who knows? We may not be alone after all!

Getting back to Earth’s facts, we are the third planet from the sun and 93 million miles away, or one AU from the sun.


Mars planet
Photo: NASA

No doubt the passion of classic sci-fi writers in the middle twentieth century, including the famous War of the Worlds broadcast by Orson Wells, Mars has driven the curiosity of life, if not now, then within this millennium. Some scientists do believe that Mars once sustained life many years ago and MASA is searching the planet with the Mars Voyager program to determine just that. If confirmed, scientists can determine that Earth is not the only planet that can sustain life, which would be probably the biggest scientific breakthrough in history!

Illustration of an extraterrestrial
Photo: iStock. Maybe intelligent life on Mars? Most likely not, but there may be microorganisms. We’re still looking to find out.

The planet is conveniently located between the Earth and Jupiter as the fourth planet from the sun at a distance of 142 million miles or 1.52 AU when it is furthest from Earth. About 39 million miles at its closest. Mars makes a complete orbit around the sun every 687 Earth days.

The two moons orbiting Mars are Phobos and Deimos.

There are plans by NASA to send men or possibly women as well to Mars.  But we better hurry up as China is also planning on manned missions to Mars as well.


Planet Jupiter
Photo by Planet Volumes on Unsplash

Besides being the largest of the eight planets, what also makes Jupiter popular is its giant red dot, which is large enough to encompass the planet Earth. It is a gigantic storm of immense proportions that has been happening since we first discovered Jupiter hundreds of years ago. This planet is so large that if it was a soccer ball, Earth would be a pea in comparison.

Jupiter is about 484 million miles, 5.2 AU from the sun.
Jupiter makes a complete orbit around the sun every 12 Earth years. Known as the ‘gas-giant’, it has no solid surface. Imagine landing on Jupiter with no solid surface!

53 moons are revolving53 moons revolving around this body.


Planet Saturn and its changing seasons
Photo: NASA

Saturn is the sixth planet from the sun (886 million miles, 9.5 AU from Earth.) Saturn makes a complete orbit around the sun every 29 Earth years. As with Jupiter, Saturn is also a gas giant with no solid surface. 82 moons are orbiting Saturn. Fifty-three of these moons have been calculated by scientists and another 29 have been located but are awaiting confirmation.

Some of Saturn’s moons are larger than the planet Mercury like the moon Titan and some are smaller than a football stadium. Saturn is probably the most popular plant with its outer rings circling it. The rings, seven in all are gaseous objects that stay intact due to the planet’s gravitational pull.


Planet Uranus
Photo: NASA

Not nearly as much fun to look at as Saturn, the planet Uranus orbits our sun at a distance of about 1.8 billion miles or 19.19 AU.

It takes Uranus to make a complete orbit around the sun in about 84 Earth years. Because of the distance from the sun, Uranus is a cold, icy planet. The planet contains 27 moons revolving around it.


Planet Neptune
Photo: Unsplash courtesy of NASA

Update 9/23/22

Neptune as seen from James Webb Telescope
Photo: NASA

On September 21, 2022, the James Webb telescope took the clearest images of Neptune’s rings so far. These images were taken with Webb’s infrared camera, so their color does not display. Instead, we see a glassy-looking mostly due to the methane gas that is so abundant. This gas is so strong that it absorbs the infrared light resulting in the planet looking rather dark, but this darkness doesn’t show because of the high-altitude clouds that are present and that is what we see in the images and are shown as bright streaks and spots because it is reflecting the sunlight.

Neptune is known as the god of the sea in Greek and Roman mythology. The planet was first discovered in 1846 and took on this name. It is 2.8 billion miles, 30.07 AU from the sun.

Like Uranus, Neptune is also a cold planet. Even colder than Uranus and is labeled as an ice giant, not a gas giant like Jupiter.  Neptune has 13 moons and has rings, although not nearly as noticeable as Saturn’s rings.

It takes Neptune 165 Earth years to revolve around the sun. And just recently, it was discovered that the temperature of Neptune unexpectedly went down. Scientists are baffled as to why. Guess we’ll just have to go there to find out!


There you have it. The eight planets are in our solar system, but we are definitely not alone. At least in solar systems that are. Based on research, there could be over one billion solar systems in our Milky Way galaxy alone. Just think about what’s out there when we consider the trillions of galaxies in our universe!

What Happens When Stars Die?

Stars forming in the Milky Way Galaxy
Stars forming in the Milky Way Galaxy. Image by WikiImages from Pixabay

A star changes into several different phases before its death. Since it is our Sun that brings us life, as well as it being part of the main sequence category of stars, let’s use the sun as our example.

Early On

During the years following the big bang, giant clouds of hydrogen and helium atoms began to form. As the years followed, these elements started to clump together to form balls of hydrogen and helium gas. In other words, they became a mass of balls of gas. When the mass is created, gravity is established and the star cycle begins.

So a star is being formed and as such, our friend gravity keeps getting stronger as the mass of the star keeps getting bigger. When gravity reaches a certain strength, the star will collapse into itself. But wait! This won’t happen because there is a force that will counter the star’s gravitational pull. So what is this mysterious force?

What Stops Stars from Collapsing?

Photo of the Sun by NASA
Our Sun. Photo by NASA on Unsplash

Enter nuclear fusion! This is where the hydrogen and helium atoms combine. Another way of describing this process is when the protons and neutrons, called nuclei of an atom (in this case hydrogen) fuse with the nuclei of another atom (in this case helium) to produce one heavier helium atom

It is that simple… or is it? For the benefit of our audience, we will keep it simple by stating that each hydrogen atom is one ounce (of course this is not the actual weight) and when four of these atoms are combined into one larger atom, the resultant atoms would weigh four ounces. But no! The weight of the combined atom ends up being less than the combined weight of the four separate atoms. So, the mass that escapes when these nuclei combine is in the form of energy

This is a prime example of Einstein’s formula E=mc2, which states that mass and energy are proportionally connected; that is, as mass decreases, energy increases and vice-versa. In the case of nuclear fusion, some of the mass of the helium nucleus is released and converted to energy. 

Another way of describing this process is when a single nucleus combines to form two lighter nuclei. When this happens, energy is released because it gives off more heat than it needs and the result is energy.

If you’d like to get more insight into the actual process of nuclear fusion, then this fun video is for you. 

So the result is that there is a balancing act where the inward pull of the star’s gravity and the outward push of the nuclear fusion process cancel out each of the forces. And that is why the Sun (and all stars) don’t collapse onto themselves (at least as long as there is hydrogen to fuel the nuclear fusion).

Let There Be Light!

If you follow the bible, God said “let there be light”. Maybe it is just a metaphor that explains what this cycle of energy is, but whether you believe in the bible or not, the fact remains that this energy that is produced is in the form of light. And there you have it! Light is created when hydrogen nuclei fuse with helium.

It’s All About Gravity

The Sun, like all stars, has a limited supply of hydrogen in its cores. When the star’s core runs out of hydrogen fuel, gravity takes hold and subsequently, the star will compress. The energy in the form of heat is then generated.

This heat caused the outer layers of the Sun to bulge out or expand across the inner part of our solar system to become what astronomers call a red giant. Big enough to engulf the orbits of Mercury and Venus and even reach Earth. Then, after millions of years, these outer layers of gas will dissipate into the darkness of the universe. 

But let’s get back to what’s left of the star. It will collapse within itself to become a white dwarf, thanks again to gravity. As an example, picture a balloon that contains solid rock (it is just gas, but for this hyper-theoretical explanation, we will use a solid) that is pushed down to the size of a ping-pong ball. 

This is referred to as a change in volume, which means that the same amount of rock in the balloon is condensed to the pong size. In scientific terms, it refers to the volume of the mass that is condensed (to a smaller size) and so, the tiny ball still weighs the same as when it was balloon size. The result is a heavier density of the mass which would be equivalent to that of one teaspoon of the material in the ping-pong ball that could weigh up to 100 tons. Over billions of years, the white dwarf cools and becomes invisible.

What About the Other Stars

Photo of a nebula
Image by Gerd Altmann from Pixabay

Now, let’s take a look at what happens to other stars in the universe. It all depends upon what size the star is during its main life cycle. 

Superlarge stars will change into supernovae, not like our sun which is considered an average star. Its end life cycle will result in a white dwarf as we discussed.  Regardless of the star’s size, all will follow a seven-cycle process. So without further ado, here are the life (and death) cycles of all stars.

1. Giant Gas Cloud

Lagoon Nebula
Lagoon Nebula in the constellation Sagittarius. Image by WikiImages from Pixabay

Nebulas are where stars are born. Similar to a fetus in a womb, the stars grow as the gas molecules work to form them. That is why it is called a gas cloud and we can thank gravity for bringing these molecules together.

2. Protostar

When the gas particles run into each other, heat is created. This result is what scientists call a Protostar – the beginning of a star’s creation. We can view this process via infrared since protostars show up warmer than the other materials in the nebula cloud.

3. T-Tauri Phase

T-Tauri stars are the next phase in the star’s life process, but not strong enough for nuclear fusion to begin. This cycle lasts about 100 million years.

4. Main Sequence

Welcome to the main sequence phase of stars and this is where our Sun is now; otherwise, you would not be here to read this article. Scientifically, it is the process where the core temperature has gone high enough to allow nuclear fusion to begin.

5. Red Giant

When the hydrogen fuel starts to run out, the nuclear fusion process will end its cycle. Now there is nothing to stop the star from condensing into itself because our friend – gravity has complete control with no force to counter it.

As the star contracts inward, the outer layers expand. This expansion is so great that it could reach the orbits of some of its inner planets.

Say hello to the red giant! When stars reach this phase, they appear yellowish since they are cooler than stars that are in their main-sequence stage.

6. The Fusion of Iron

The Helium molecules start combining at the star’s core, causing the core to shrink. When this happens, carbon is fused in and this process continues until the atoms turn into iron. Now the core will collapse as the iron fusion absorbs energy. This in turn causes this red giant to become a supernova., but for medium-sized stars like our Sun, the star will contract and turn into a white dwarf.

7. Supernovae 

Illustration of a supernova explosion
Illustration of a supernova explosion. Image by Gerd Altmann from Pixabay

Some of the most spectacular events in galaxies is the occurrence of supernovae. In this phase, most of the star’s matter is blasted away into space, creating a giant blast that even the human eye can detect if it is within viewing distance.

What is happening is that the star runs out of energy; in other words, it is depleted of its fuel and subsequently collapses into itself, with all the electrons and protons compressing into a neutron and subsequently becoming a neutron star.

8. Stellar Nursery

No doubt you have seen nebulas in photos or maybe through a telescope. These are the stellar nurseries, where remnants of gas and other materials are floating around only to be gathered together again to form new stars.

Illustration of a star's life cycle
Illustration of a star’s life cycle


Andromeda – Our Nearest Spiral Galaxy

Photo of Andromoda Galaxy
Andromeda Galaxy. 220,000 light-years across, containing 10 trillion stars. This image was captured using amateur astrophotography equipment including a Skywatcher 80mm telescope, a QHY269M monochrome camera, and a seven-position filter wheel containing Red, Green, Blue, Hydrogen Alpha, Oxygen III, and Sulphur II filters. Tracking was done using an iOptron CEM70G mount and PHD2 guiding software. It was entirely processed using PixInsight. iStock.

A Galaxy of 1 Trillion Stars!

What was the subject of the popular heated debate between ace astronomers, Heber Curtis, and Harlow Shapley? – The Andromeda galaxy!

Back in 1920, Shapley believed that the Pinwheel and the Andromeda galaxies were nebulae found in the Milky Way. Curtis believed that this wasn’t the case, based on the argument that the Andromeda galaxy is at a multi-million light-year distance from our Milky Way. It was later established through the work of Henrietta Leavitt, Edwin Hubble, and others that Curtis indeed was right.

It has since been determined that this galaxy has over one trillion stars. With that amount of stars and with scientists’ estimates that up to 50% of the planets that revolve around these stars may be in the Goldilocks Zone, we have an astounding possibility of life somewhere in Andromeda.

Over the years, a lot of astronomers have researched Andromeda with some of the findings listed below.

Once a Nebula?

Lagoon Nebula
Lagoon Nebula in the constellation Sagittarius. Image by WikiImages from Pixabay

Long before the actual expanse of the universe was realized, the rim of the Milky Way was considered to be the boundary of outer space. Within those boundaries, the fuzzy blur visible in the sky
(Andromeda) was believed to be a cluster of cosmic dust clouds forming stars. The galaxy was originally named the Great Andromeda Nebula until the powerful telescopes of the 20th century proved otherwise.

It Can Be Seen From Earth

This mammoth, dazzling galaxy is at least a 2.5 million light-year distance away from us. However, if you find a clear night sky (the pollution levels need to be down too) you can see the galaxy with the naked eye. It would appear as a scattered haze. Grab a pair of good binoculars, look towards the constellation Cassiopeia and you can witness the central region of the galaxy. A large powerful telescope will leave you in awe of the spectacular view of Andromeda.

It is Gigantic

The galaxy has a diameter that stretched across almost 220,000 light-years. A colossal structure that seems longer than the full moon at night and is 2.5 times longer in length than the entire Milky Way. It is farther than any other star visible from the earth, yet it can still be seen with the naked eye.

It is believed that the Milky Way is the most immense body in the Local Group (a galactic group based on more than 54 galaxies), but Andromeda takes the cake when it comes to being more voluminous. It contains trillions of stars, twice as many as the ones in our galaxy. It was the Spritzer Space Telescope that made this observation.

We’ve Known About It for a Lifetime

The Andromeda galaxy is visible in the night sky and has been constantly scrutinized, observed, and studied by astronomers for multiple decades.

The galaxy spawned about 10 billion years ago when several smaller protogalaxies merged together. About some 8 billion years ago it collided head-on with another galaxy that led to the formation of the giant that is Andromeda today.

Now here’s the fun part.  Andromeda is moving toward our galaxy. And it’s not just moving – it’s actually on a collision course! 

Let that sink in. Andromeda and the Milky Way are both moving toward each other at a speed of 120 kilometers per second. But here’s the catch: at this rate, it’ll take around 4 billion years for the galaxies to collide!


Three of the Most Popular Constellations

Illustration of the constellations around Earth
Detailed constellation map of the Southern Hemisphere with names of stars. Photo: IStock

Sky Patterns

It’s a beautiful clear night and you gaze up at the sky. What do you see? Thousands of stars and perhaps even galaxies. Let’s use our imagination, just as the ancient Greeks had done, and let our creativity loose. Now, what do you see? A cow? A frog? A man with a sword?

If you see patterns, great! But if you don’t, no worries. We’ll let you know what the ancient Greeks discovered millennia ago and are still in use today.

Enter the Constellations

Constellations with figures drawn around the stats
Photo IStock

Constellations are officially defined as clusters of stars that make identifiable patterns for human clarification. There are a total of 88 constellations or to be a bit more creative, stars that make up characters that have been officially documented. The constellation Orion is the most well-known.

The term was coined from the Latin word constellti and was first used in astrology. The earliest records date from the Middle Bronze Dynasties from the Bronze Age which dates back from 2055 to 1650 BC. It is noted in the bible as Job 9:9, 38:31-32 – the “Maker of the Bear“.  In Greek mythology, the Orion Constellation represents a hunter.

Within some of these constellations and sometimes spanning across them are smaller star patterns called asterisms. An asterism is a group of stars that form figures but are not large enough to be called a constellation.

Most Popular Constellations

We won’t discuss all of the 88 constellations, but we will pick a few that are the most well-known.

Let’s Start with Orion

The ‘Hunter’ in the Orion constellation as imagined by the ancient Greeks’ Photo: IStock

In the Orion constellation, we have the Orion Nebula, which is a group of gas and dust that will form stars, some of which have already been formed.

Designated as Messier 42, we have the star Betelgeuse which is 642.5 light-years from Earth. It is a supergiant star and the second brightest star in Orion. It is located at the top left, near the top of the mythical hunter’s arm. Additionally, we have stars Saiph, Bellatrix, and Rigel to name a few more.

You might be familiar with Rigel, the crew of the Star Ship Enterprise talks about how they love to go there. Of course, it is not the star Rigel that they are visiting, but, the fourth planet revolving around it, called Rigel 4, a Goldilocks zone planet or “Class M” as Mr. Spock would say.

As mentioned, the  Constellation Orion represents the mythological Greek hunter Homer. The easiest way is to find the three stars that are aligned with each other. They are Alnilam, Mintaka, and Alnitak, known as Orion’s Belt, which is at the center of Homer’s body.

On a clear night, from the northern hemisphere, just look up north. Of course, you need to be in a low-lit, wide-open location. Even if you live in a city, open areas such as parks can help you locate this popular constellation.

Ursa Major – King of the Greek Gods

Another famous constellation is Ursa Major. Latin for Great She-Bear and more popularly known to be the constellation where The Big Dipper lies, probably the most popular of all asterisms. Also known in the UK as the Plough. 

The Big Dipper is well known mostly because of its navigation capabilities. If you are in the Northern Hemisphere, which is above the 35th parallel, you should be able to see it but to be a bit more realistic, those who are north of  Tennessee’s southern border should be able to find it more easily.

When you look at the Big Dipper, you may not notice it, but this and the Little Dipper rotate around a star called Polaris, otherwise known as the North Star, which is one of the brightest stars in Ursa Major.

A child once mentioned that his mother told him whenever he felt sad, he should look up at the North Star and he will know he is being watched over. Parents, whether true or not, you may want to try this! Besides keeping him or her less stressed, they may learn something about the constellations and perhaps astronomy as well! Who knows? Your son or daughter may become a rocket scientist celebrity!

Let’s look back up to see where Polaris is located. It lies at the end of the handle of the Little Dipper. Now try drawing an imaginary line around the big dipper to form a Great Bear. Do you see it?

A Point of Navigation

The Big Dipper serves as a pointer to other locations in the sky. “Follow the Arc to Arcturus” is a fairly popular expression in navigation and astronomy. The “arc” can be envisioned as a curved line from the bottom of the Big Dipper and helps you locate two other popular stars called Arcturus and Spica.

So Ursa Major is quite a constellation that contains both the Little Dipper and the Big Dipper. The next time you head out, drop your GPS and compass and see if you can navigate with these stars!

The Zodiaseveral

Not a constellation, but worth mentioning before we continue discussing onward, so let’s talk about the Zodiac. This is a group of stars that cross several constellations at the vernal equinox, defined when the Earth’s rotational axis reaches a particular position and occurs in March. At this point, the following occurs:

    • The northern and southern hemispheres receive the sun’s rays equally
    • Night and day are equal in length
    • Spring begins

Aries – The Ram

Aries is a constellation that is not as bright as some of the others; however, it is found in the northern hemisphere, but you may need binoculars or a telescope to find this one since only a few of its stars are visible to the naked eye.

Aries is one of the constellations that lie along the Zodiac and means “the ram” in Latin. The symbol for this constellation is the imaginary set of lines that form a ram’s horns.

Aries has a narrative behind it. It is the story of the Golden Fleece. The mythical story of Jason and the Argonauts is about the search for the Golden Fleece.

Aries contains the stars Hamal and Sheratan and interestingly enough, it also contains the spiral galaxy NGC 772 and the dwarf galaxy NGC 1156.

Orion, Ursa Major, and Aries

These are three of the most popular constellations in our night sky. We hope you gained some perspective on how the constellations came to be, their importance in navigation, their relation to astronomy, as well as a bit of Greek mythology, and some of the stars and galaxies that are contained within them. Have we sparked your interest? How about going outside to see if you can spot the Greek hunter, the Great Bear, and the ram’s horns?