Two is a very specific type of planet. It has no natural moons, or natural orbiting bodies that could orbit it. These two planets are very unique in this way.
Two-planet systems are a rare sight in the cosmos, seeing as there are only two types of planets: small, portable worlds that can be transferred between systems and locations, and large land masses that require stable orbits to remain stable.
These large lands masses require a support system in the form of another planet or body to stabilize its orbit. This other body must be small enough for it to be an occasional transfer world, around which it can develop a population and maintain a government.
This other body must have the right composition and location for a home world, though—one that does not need to be as stable as our own Earth but can still provide some relief when one of the planets is unhappy.
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Mercury
Although Mercury has a little moon, it doesn’t orbit Mercury. Instead, it moves in and out of the planet’s atmosphere at a fairly steady clip.
At over sixty miles in diameter, Mercury is the second smallest planet in the Solar System. It takes just over four days for it to rotate around its axis, making it feel cold and solid.
Because of its small size, how fast it rotates, and how little distance it gets from the Sun, there is not very much heat from Mercury out into space. It does have a seasons, as there are winter and summer times on Earth.
There are no land or water features on Mercury, just like Earth. Because of how small Earth is, there is not enough relief to have any oceans or land either.
Earth
With a diameter of over one thousand miles, Jupiter is by far the largest object in our solar system. It is also one of the brightest objects in the sky.
When viewed from a distance, Jupiter looks almost full. This is because it appears to move as you look away from it. While it remains stable, this appearance comes from its large scale and constant movement across the sky.
The moon can make a big difference in how bright an object is. Because Earth rotates on its axis once every day, nothing more than an hour and a half passes by on Jupiter when we are on Earth.
Because of this, some moons appear much brighter than they really are because of daylight time differences. For example, Deimos looked much brighter during daytime coverage than it does at night due to this effect.
Mars
Mars is a red planet. It has two ring-like features around its diameter, one closer to its center and one farther away.
The closer ring is called the “sapphire” ring. The farther ring is called the “indigo” ring. Both are permanent, but the closer ring has shorter life spans than the farther one.
The nearer ring was recently broken off and re-assembled, which is why it has a shorter lifespan. It took place back in 2007 and 2008, when scientists believed that there were once living things on Mars. There were no signs of life until that event took place.
Because of this event, we now know that Mars had a green climate history ago. There was life, and there were long periods where it was warm enough for plant growth to take place.
Jupiter
Jupiter is the second biggest planet in the Solar System. It has five moons, making it the fourth largest planet in the solar system.
Jupiter is a very large planet. It is twice as long as it is wide and has many beautiful features, such as massive volcanic oceans and towering clouds.
One of those features that looks like a cloud is Jupiter. It has a colourful disk that you can look at from many places in the sky.
You can find Jupiter easiest between midnight and six am because that is when most people are sleeping. Also, because Jupiter lies in the middle of the sky when you are awake, you will see it better than you would at other times of the day.
Many people use telescopes to see if there are any planets around Jupiter.
Saturn
Saturn, the largest planet in the Solar System, has no natural moons. This is a rare case where a planet has an orbital slot that is not occupied by another body.
Saturn was once home to multiple small planetary bodies that joined together to form its largest moon, Ganymede. These bodies were rounded and small, making it hard to detect them.
Today, these tiny objects are just one small piece of Saturn. It is difficult to detect even the smallest of objects in Saturn, making two planets seem more striking than they actually are.
However, there may be life on these two planets. A recent study found evidence of liquid water on two distant planets close to Saturn. This water could be hospitable for life, as it could be in cold regions of space.
Uranus
Uranus is a large, pink-hued planet. It is almost impossible to miss! Because it has no natural satellites, it is visible from Earth with the naked eye!
Uranus was one of the first planets to be discovered. In 1781, Johann von Lindewig found it in a book he was reading, The Starry Messenger. He believed it to be a star but in 1846 William Huggins discovered its satellite Titania.
Titania is another frozen world that orbits Saturn so closely that they are considered one system. It takes about 6 days for Titania to orbit Saturn, making their distance between them only about 122 million miles! This close relationship makes Titania an important probe for research into Saturn and its moons.
Since 1970s, there have been many probes that visit Uranus. These include the Pioneer and Voyager spacecraft, which made their journeys in the late 70s and early 80s, respectively. In 1989, NASA launched Icy Moon (Titania) probe to study Pluto’s moon Callisto.
Neptune
Neptune is a planet that looks like a blue sea. It has no moons, making it the only one with no natural environment support.
The only way to get enough heat and sunlight to thrive is via rockets. This is not an option for most people, as they need water and food to survive.
Because Neptune has no natural environment support, it does not have any protective ideologies like governments or religions can use to guide its people. People are left to their own devices to find what they are looking for and live their lives!
Many people think Neptune is scary because there aren’t many people on it.
Pluto
Pluto, the last planet in our list of invisible planets, has no natural satellite or neighbor. It is the only planet that is officially classified as a dwarf planet (Pluto is much smaller than a Jupiter-sized planet).
Despite its rare status, people are definitely fascinated by Pluto. It has been the center of attention for scientists and public figures since 1992, when a spacecraft called New Frontiers Foundations released data on it.
Since then, New Frontiers Foundations has updated and re-released data on Pluto, adding and changing things about it. For instance, in 1992, they said there was hydrothermal activity on Pluto, but newer data showed nothing existed.
So, what does New Frontiers Foundation say Pluto is? It says it is an ice-covered world with hot springs that may have been created by solar radiation. This makes sense because earlier measurements showed heaters were active.