The solar system began as a cloud of dust and gas known as a solar nebula around 4.6 billion years ago. As the material began to spin, gravity compressed it in on itself, generating the sun at the center of the nebula. Small particles were attracted together and bonded together by gravity to form bigger particles. These aggregates later formed planets that retain evidence of their creation (i.e., craters).
The Earth and other planets migrated away from the sun during this early stage of solar system formation. The most distant planet from the sun at its closest approach was Uranus, which orbits the sun every 84 million years. Neptune, which has a more distant orbit and longer period, followed close behind.
As time went on, more mass was pulled into these central regions of the solar nebula, forming a star at its core. The sun developed enough power to blow off its outer layers, forming a bubble of gas and dust called an accretion disk. This disk is how our galaxy gained its stellar mass before the onset of galactic evolution.
The solar system is now inside of this accretion disk. All of the planets except for Earth are covered by this disk. The Sun rises due to light radiation emitted by hot objects becoming energized when they pass through or are attached to cold objects. For Earth, this process does not happen because we are warm due to the heat of radioactive materials within us that originated from the sun.
About 4.5 billion years ago, a massive, revolving cloud of gas and dust known as a solar nebula produced the Sun and the rest of the solar system. The nebula whirled faster and flattened into a disk as it collapsed due to its overpowering gravity.
As the solar nebula cooled down, large molecules formed first, then smaller ones. At some point, enough small particles had accumulated to form a nucleus - which can be any object larger than about 10 miles (16 km) that is composed mainly of carbon and hydrogen atoms. This nucleus could be a single atom or a molecule. If it's a molecule, it must have at least four atoms attached to it.
The next step is called "condensation." Once the temperature drops low enough for atoms to stick to their neighbors, clouds of gas and dust can collapse under their own weight and form objects that contain much more mass than ordinary gases do. As these objects grow larger, they become stars.
Stars are so heavy that they cannot be supported solely by the force of electromagnetic pressure: instead, they require a dense core of particles held together by the force of gravity. This core is called an "astronomical unit" or "AU." It contains about 2% of the star's mass but almost all of its volume.
Our solar system evolved from a thick cloud of interstellar gas and dust some 4.5 billion years ago. When this dust cloud disintegrated, it created a solar nebula, which is a whirling, swirling disk of material. Gravity drew more and more material into the center. The resulting ball of matter was called Earth, or baryonic Earth.
As Earth condensed, heavy elements such as iron and nickel were forced deep into its core. These elements formed the basis for future planets to come. The rest of Earth's mass remained near the surface where water could have continued to evaporate and flow into large bodies like Antarctica today.
The formation of the solar system was not only important for understanding how galaxies work but also for determining our own planet's fate. If Earth had not been able to hold on to its atmosphere, we would now be living under a thick layer of ice.
The collapse of the solar nebula around Earth caused the formation of the Moon. Since Earth's mass was larger than the Sun's, there was no need for a moon made of lighter material than Earth. Instead, the lunar crust and mantle are said to be "robust" forms of terrestrial matter - that is, they are found on Earth.
It is estimated that if Earth had been given enough time, all of its oxygen would have been consumed by hydrogen atoms.
Around 4.5 billion years ago, Formation.
The Sun is now well on its way to becoming a red giant. When it does, it will use up all the hydrogen in its core and then expand so much that even its helium nucleus will be squeezed until it collapses into a compact mass. This will cause the Sun to shine more intensely for a few hundred thousand years before it explodes.
The Earth's atmosphere protects us from most of the damage of this explosion but elements such as iodine and xenon are destroyed by the blast. These gases are used in radiation detectors designed to look for nuclear activity around other stars. Iodine is also used in satellite communication systems because it allows many more messages to be sent over greater distances than other elements such as carbon or aluminum.
Even though the Sun will become a red giant later this century it will still be able to burn hydrogen atoms for another 5 billion years or so. By this time, the Earth will have been transformed into a cold and dry planet not suitable for life as we know it. But if you go back far enough in time, the Earth was warmer and had an ocean covering nearly half of its surface.
Formation. As you might expect, there are different theories about what happened next. Some scientists think that a giant impact may have destroyed much of the solar nebula, but others believe that the heat from the young Sun could have thawed most of it free from any solid particles.
The most accepted theory is that many millions of years later, the heat from the newborn Sun began to evaporate any remaining molecules from the collapsing nebula. In this way, the planets were created.
Even though we can't see them with our eyes, there are billions of stars in the Universe. Many of these stars are like our Sun, while some are so hot that they give off light alone. It's thought that during its life, our Sun will go through a phase where it becomes a red giant, shedding its outer layers into space. When it does, it will swell up to about nine times its current size and shine more brightly than today. This will happen about 5 million years from now.
More than 4.5 billion years ago, a cloud of dust and gas known as a nebula imploded under its own gravity, resulting in the formation of the sun. As it spun, the cloud flattened into a disk, with our sun developing in the middle. The fringes of the disk eventually accreted into our solar system, including Earth and the other planets. The sun is a main source of energy for Earth's ecosystems.
From space, the sun appears as a bright object against the darker background of the night sky. It is usually about the size of a half dollar held at arm's length, but it can grow larger or smaller depending on how far away it is from Earth.
The color of the sun varies over time. On average, it is white or light blue, but it can also be red, orange, or yellow when it is angry. These colors are caused by elements such as iron and oxygen which make up most of our planet and the atmosphere that surrounds it. As well as being pretty, this helps scientists understand how Earth's environment changes over time.
The brightness of the sun has been increasing over time due to effects like more carbon dioxide in Earth's atmosphere and water vapor in the air. By about a quarter past one in the morning, sunlight is now almost as bright as it was during midday. This means that if you were outside during these hours you would need a dark space around you with no shadows to see what time it is.