Every scrap of matter in our solar system originated as part of a giant interstellar cloud. As it grew hot and dense, gravity began to pull dust and gas inwards.
Gravity sculpted this material into the planets, as well as smaller bodies such as asteroids, comets and meteoroids. Some of these objects are still tumbling through interstellar space today.
The Sun
The Sun and the entire solar system orbits around the center of our Milky Way galaxy.
The average speed is 828,000 km/hr or 448,000 mph (716,000 km/h). It will take 230 million years for the solar system to complete one full orbit.
The hottest part of the Sun is its core, where hydrogen fuses to form helium through nuclear reactions. Temperatures here reach 27 million degF (15 million degC).
The Moon
The Moon is Earth’s natural satellite, orbiting us in an elliptical orbit. Over time, the Moon rocks a little from north to south and wobbles a bit from east to west.
These minor tidal effects aren’t enough to slow the Moon down as it moves through space. It will continue to orbit Earth for millions of years, unless something happens.
Mercury
Mercury is a tiny planet in the Solar System that takes about 59 Earth days to rotate on its axis. It orbits the Sun, and in the process it passes close to the Sun, thus causing some disturbances in its atmosphere and magnetic field.
The resulting effect appears as a gyration, or precession, of its orbital path. This motion, about 9.5′ (0.2deg) of arc per century, is a test of the general theory of relativity and is one of the most significant confirmations to date of this theory.
Venus
Venus is the second planet from the Sun and Earth’s closest planetary neighbor. It has a thick atmosphere dominated by carbon dioxide, though it does have a small percentage of nitrogen.
Unlike most other planets, Venus orbits the Sun clockwise on its axis. This is due to a collision in the early part of its life.
Earth
The Earth rotates on its axis and orbits the Sun. One rotation takes about 365 days, or one year.
Scientists have studied these motions to understand how the solar system moves through space. But it’s still unclear how the planets move relative to each other.
Mars
Mars, the fourth planet from the Sun, is a dry, rocky world. It’s also the closest planet to Earth and home to a new rover that’s searching for signs of past life.
Getting to Mars involves travelling through space using several different orbits and manoeuvres. One is called the Hohmann transfer, and it’s the most fuel-efficient way to travel between the two planets.
Jupiter
Jupiter’s fast rotation – it completes a single day in less than 10 hours – creates strong jet streams that separate the planet’s clouds into long bands of bright and dark material.
These jet streams reach depths of 2,000 miles (roughly 3,200 kilometers). They are similar to the jet streams that form on Earth, but at far higher latitudes.
Saturn
Saturn is the second-largest planet in our solar system. It is a gas giant made up of mostly hydrogen and helium.
A large percentage of its mass is in its liquid metallic core that lies deep inside the planet’s interior.
Like the other gas giants in our solar system, Saturn has a dense outer core of metals like iron and nickel. Then, a layer of liquid metallic hydrogen covers that.
Uranus
Uranus is an ice giant and one of the outer planets in the solar system. It receives 360 times less light and heat from the Sun than Earth.
It has an extensive satellite system, including several moons. The largest of these are Oberon and Titania.
Neptune
The Solar System is an assemblage of eight planets, many asteroids, and a vast reach of highly tenuous gas and dust known as the interplanetary medium.
The Sun influences the motion of all these bodies, which orbit it in elliptical orbits.
Neptune is a blue gas giant, the eighth planet from the Sun. It has a rocky core, and its surface is covered with a thick atmosphere.
The Sun is the centre of a Solar System that formed 4.6 billion years ago from the collapse of a giant interstellar molecular cloud.
The solar system is home to eight planets, their moons, asteroids, dwarf planets, the Kuiper belt and a variety of other small bodies, including micrometeoroids, comets and interplanetary dust particles.
The Sun
The Sun is the center of our solar system, and it’s our primary source of heat, light and energy. It also generates a magnetic field that extends into space, forming a large bubble called the heliosphere. This field carries matter and energy to neighboring stars, and it eventually slows down at a theoretical boundary called the heliopause.
Our Sun formed 4.5 billion years ago, as the remnants of a cloud of gas and dust in the Milky Way galaxy collided to form a young star. The star grew larger and older until it became the massive, bright Sun we see today. Its mass is about eight times that of Earth, and its gravity is powerful enough to hold planets and other objects in orbit around it.
Three quarters of the Sun’s mass is hydrogen, which fuses to create helium in a process called nuclear fusion. The difference in mass between the atoms of hydrogen and those of helium is released as energy, which is how the Sun produces all of the heat and light that sustain life on Earth.
About 1.69 percent of the Sun’s mass is made up of other gases and metals, like iron, nickel, oxygen, silicon, sulfur and magnesium. These make up a thin layer called the photosphere, which is about 400 kilometers (250 miles) thick and reaches temperatures of 6,000 kelvins.
Above the photosphere is the chromosphere, a thicker region that looks red in reflected light. This layer is where the Sun’s plasma streams narrow and morph into a crown-like structure called the corona. The corona is incredibly hot, reaching temperatures of about 14,000 kelvins.
In addition to the photosphere and chromosphere, the Sun’s magnetic field causes various effects throughout the year, known collectively as solar activity. The most common are solar flares and coronal mass ejections, which can release a vast amount of energy.
The Sun’s heliosphere is also the source of the solar wind, a stream of energetic particles that flows outward from the sun in all directions. These wind particles travel billions of kilometers before they slow down at a theoretical boundary called the helopause.
The Moon
The Moon is a rocky body that orbits Earth at an average distance of 384,000 km (238,600 miles). It has a diameter of about 1,738 km (1,000 miles) and is slightly flattened by its elliptical orbit.
It has a surface that is a mixture of a molten rock called regolith, a solidified layer of lava, and a thick crust of rocky material. This crust contains minerals like olivine and pyroxene, as well as magnesium, iron, silicon, calcium, aluminum, and oxygen atoms.
Astronomers think that the Moon formed around 4.5 billion years ago when two spinning planets collided. The debris left behind by that impact is what makes up the Moon we see today.
Computer simulations of this collision show that it formed a large dust cloud that spun in the same direction as the Sun, even after a very long time. This is one of the reasons the Moon has been able to retain its angular momentum ever since it was formed.
In recent years, scientists have discovered that the Moon has a very thin atmosphere of gases including helium, argon, neon, ammonia, methane, and carbon dioxide. This is a surprise because most of these gases are not found in the planets’ atmospheres.
The moon also has ice on its surface, which is made up of minerals like olivine and pyroxene. Scientists aren’t sure what causes it to form, but they believe that it could have been delivered from comets or other sources of water ice.
Another interesting fact about the Moon is that it is moving away from Earth at a rate of 3.8cm per year. This is caused by the effect of its gravity on the rotating Earth.
On a clear night, the Moon is bright enough to be seen. However, the Moon’s appearance from Earth changes dramatically over the course of a night as it varies its phase.
This means that it is changing from a crescent to a full moon, and then back again, as its light reflects off different parts of the Moon. The phases of the Moon can be spotted by looking at where the moon is in relation to stars in the night sky on one night, and then comparing it with a few hours later on another night.
The Earth
The Earth moves through space in a number of ways. The most obvious is that it rotates around its own axis, called the equator, every 24 hours. This rotation causes the sun to rise in the east and set in the west as it travels across the sky.
In addition, the earth is moving in its orbit around the sun at a speed of about 67,000 miles per hour. This movement is primarily caused by the solar wind, a stream of particles created by the sun and other stars in the nearby region. The solar wind is also responsible for affecting the motion of comets, which are objects that orbit other stars.
Earth’s axis is slightly oblate, which means that it displays a bulge at the equator. This oblateness is caused primarily by the sun’s gravity, but it also has a small influence from the moon.
Eventually, the planet’s oblateness will cause its axis to incline (precess) at an angle of 90 degrees relative to the plane of its orbit. The resulting precession is a periodic planetary motion that happens over 26,000 years.
The Earth also moves in a few other short-term motions. These include a periodic sway of the North and South Poles, a yearly circular motion, and a steady drift toward the west due to fluid movements in the planet’s mantle.
Another way that the Earth moves in space is by traveling through the Oort Cloud, a region of space between the sun and the outer edge of the galaxy. This region contains gaseous and ice-rich debris that is left over from the formation of our solar system, along with dust and other tiny matter that has been scattered into space.
As a result, the Earth’s orbit is slightly curved and its position in the Oort Cloud changes over time. This is a normal part of the planet’s orbit, but it can have an impact on its polar regions and surface, including weather and water conditions.
In the end, Earth is still spinning at its original speed, which will keep it a stable planet for the next few billion years. As it spins, the Earth’s atmosphere will continue to move and its surface will keep changing, too.
The Planets
The Solar System is made up of eight planets – four of which are rocky (Mercury, Venus, Earth and Mars) and four gas giants (Jupiter, Saturn, Uranus and Neptune). There are also hundreds of smaller bodies of rock and ice in the outer reaches of the solar system.
When the Solar System formed, it was a spinning cloud of gases and dust that revolved around a star at its center. As the cloud collapsed, some of the gas escaped out into space while the remaining matter slowly clumped together. The clumps began to spin faster under their own gravity, and eventually accumulated to form the planets.
Each planet whizzes around the Sun at a speed that allows it to circle without spiraling into the Sun or whirling away into space. That speed is the result of a strong internal force that pulls at each planet’s mass from the center, tugging it in on itself and keeping it in orbit.
The planets’ circular motion is the result of their early formation, and it is still acting on them today as they move through the interplanetary medium. The solar wind, the plasma stream of particles and energy streaming from the Sun and occasional planetary eruptions, contribute to this movement.
This motion is a very complicated process that takes billions of years to complete. There are many different forces at work, including gravity, and the inertia of the early explosion that set everything in our solar system in motion.
There is a lot going on at once, and things are changing all the time. This is why there is no way to know for sure how our Solar System will look in the future.
Some of the planets have changed dramatically in size, shape and composition since they were first discovered. Pluto, for example, was once considered a planet but is now a dwarf planet.
The outer planets, Jupiter, Saturn and Uranus, have large gaseous cores. They are called gas giants because they have a lot of gaseous material, like hydrogen, helium and ammonia.
In addition, they have solid surfaces that may have been shaped by impact with other objects. Some of them have moons, which are tiny planets that move around their parent planet in the same direction as the planet.
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