Before it was moulded into a neat set of planets, every scrap of matter in the solar system was part of a gigantic nebula - a floating interstellar cloud. This giant cloud was made up of dust, hydrogen, and other gases. It began to collapse in on itself after becoming gravitationally unstable.
This was possibly because of a nearby supernova - an exploding star - sending shock waves rippling through space. Gravity then caused dust and gas to be continually tugged to the centre of the cloud, making its core very hot and dense. Gregory says, 'It became a snowball effect.
As more matter got pulled in, the centre got denser, increasing the gravity and pulling even more dust inwards. Once the centre became hot and dense enough it triggered nuclear fusion. Then visible light flooded the solar system for the first time. This flat disc, called the protoplanetary disc, was where the planets formed. As this rotating disc span around the Sun, it began to cool and form different types of solid material.
Gregory says, 'Near to the Sun, the temperature was very high, so minerals and metals formed. And on the edge of the disc, far away from the heat of the Sun, less volatile solids like ice and ammonia formed. Gradually they got larger and larger, sweeping up all the leftover dust, until they grew into the planets we recognise today.
Part of a chondrite found in the Sahara desert, showing the formation of chondrules. The hot, rocky material near the centre of the solar system was sculpted into terrestrial planets with metal cores: Mercury, Venus, Earth and Mars.
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By studying several things, mostly meteorites, and using radioactive dating techniques, specifically looking at daughter isotopes, scientists have determined that the Solar System is 4. Well, give or take a few million years. That age can be extended to most of the objects and material in the Solar System. The basics of it are that all material radioactively decays into a stable isotope.
Some elements decay within nanoseconds while others have projected half-lives of over billion years. The heliosphere is the bubble created by the solar wind — a stream of electrically charged gas blowing outward from the Sun in all directions. The boundary where the solar wind is abruptly slowed by pressure from interstellar gases is called the termination shock. This edge occurs between astronomical units. Voyager 1 went interstellar in and Voyager 2 joined it in But it will be many thousands of years before the two Voyagers exit the Oort Cloud.
There are more than known moons in our solar system and several more awaiting confirmation of discovery. Of the eight planets, Mercury and Venus are the only ones with no moons. In some ways, the swarms of moons around these worlds resemble mini versions of our solar system. Pluto, smaller than our own moon, has five moons in its orbit, including the Charon, a moon so large it makes Pluto wobble.
Even tiny asteroids can have moons. In , scientists found asteroid Florence had two tiny moons. Our solar system formed about 4. The cloud collapsed, possibly due to the shockwave of a nearby exploding star, called a supernova. When this dust cloud collapsed, it formed a solar nebula — a spinning, swirling disk of material.
At the center, gravity pulled more and more material in. Eventually, the pressure in the core was so great that hydrogen atoms began to combine and form helium, releasing a tremendous amount of energy.
Matter farther out in the disk was also clumping together. These clumps smashed into one another, forming larger and larger objects.
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