How The Life Begin

Subsequent evolution The planets were originally thought to have formed in or near their current orbits. From that, a minimum mass of the nebula i.e. the protoplanetary disc was derived that was necessary to form the planets – the minimum mass solar nebula. It was derived that the nebula mass must have exceeded 3585 times that of the Earth. However, this has been questioned during the last 20 years. Currently, many planetary scientists think that the Solar System might have looked very different after its initial formation: several objects at least as massive as Mercury were present in the inner Solar System, the outer Solar System was much more compact than it is now, and the  Kuiper belt  was much closer to the Sun. Terrestrial planets At the end of the planetary formation epoch, the inner Solar System was populated by 50–100 Moon- to Mars-sized  planetary embryos . Further growth was possible only because these bodies collided and merged, which took les...

The  giantplanets  ( Jupiter ,  Saturn ,  Uranus , and  Neptune ) formed further out, beyond the  frost line , which is the point between the orbits of Mars and Jupiter where the material is cool enough for volatile icy compounds to remain solid. The ices that formed the Jovian planets were more abundant than the metals and silicates that formed the terrestrial planets, allowing the giant planets to grow massive enough to capture hydrogen and helium, the lightest and most  abundant elements. Planetesimals beyond the frost line accumulated up to 4  M ⊕  within about 3 million years.  Today, the four giant planets comprise just under 99% of all the mass orbiting the Sun. heorists believe it is no accident that Jupiter lies just beyond the frost line. Because the frost line accumulated large amounts of water via evaporation from infalling icy material, it created a region of lower pressure that increased the speed of orbiting dust part...

Formation of the planets See also:  Protoplanetary disk The various planets are thought to have formed from the solar nebula, the disc-shaped cloud of gas and dust left over from the Sun's formation. The currently accepted method by which the planets formed is  accretion , in which the planets began as dust grains in orbit around the central protostar. Through direct contact, these grains formed into clumps up to 200 metres in diameter, which in turn collided to form larger bodies ( planetesimals ) of ~10 kilometres (km) in size. These gradually increased through further collisions, growing at the rate of centimetres per year over the course of the next few million years. The  inner Solar System , the region of the Solar System inside 4 AU, was too warm for volatile molecules like water and methane to condense, so the planetesimals that formed there could only form from compounds with high melting points, such as metals (like  iron ,  nick...

Pre-solar nebula The nebular hypothesis says that the Solar System formed from the gravitational collapse of a fragment of a giant  molecular cloud . The cloud was about 20  parsec  (65 light years) across, while the fragments were roughly 1 parsec (three and a quarter  light-years ) across. The further collapse of the fragments led to the formation of dense cores 0.01–0.1  pc  (2,000–20,000  AU ) in size. One of these collapsing fragments (known as the  pre-solar nebula ) formed what became the Solar System. The composition of this region with a mass just over that of the Sun was about the same as that of the Sun today, with  hydrogen , along with  helium  and trace amounts of  lithium  produced by  Big Bang nucleosynthesis , forming about 98% of its mass. The remaining 2% of the mass consisted of  heavier elements  that were created by  nucleosynthesis  in earlier gen...

Formation and evolution of the Solar System Jump to navigation Jump to search Artist's conception of a  protoplanetary disk The formation and evolution of the  Solar System  began 4.6  billion years ago  with the  gravitational collapse  of a small part of a giant  molecular cloud . [1]  Most of the collapsing mass collected in the center, forming the  Sun , while the rest flattened into a  protoplanetary disk  out of which the  planets ,  moons ,  asteroids , and other  small Solar System bodies formed. This model, known as the  nebular hypothesis  was first developed in the 18th century by  Emanuel Swedenborg ,  Immanuel Kant , and  Pierre-Simon Laplace . Its subsequent development has interwoven a variety of scientific disciplines including  astronomy ,  physics ,  geology , and  planetary science . Since the dawn of the  space age ...

What If the Big Bang Wasn't the Beginning? Was the universe created with a Big Bang 13.7 billion years ago, or has it been expanding and contracting for eternity? A new paper, inspired by alternative explanations of the physics of black holes, explores the latter possibility and rejects a core tenet of the Big Bang hypothesis.   The universal origin story known as the Big Bang postulates that, 13.7 billion years ago, our universe emerged from a singularity — a point of infinite density and gravity — and that before this event, space and time did not exist (which means the Big Bang took place at no place and no time).   There is ample evidence to show that the universe did undergo an early period of rapid expansion — in a trillionth of a trillionth of a second, the universe is thought to have expanded by a factor of 10 78  in volume. For one, the universe is still expanding in every direction. The farther away an object is, the faster it ...