Our solar system was formed about 4.7 billion years ago when a cloud of gas and dust gathered into a clump that was pulled together by gravity. Over millions of years, this clump grew bigger and eventually became the Sun and planets.
The Sun is the center of our solar system and controls everything that happens in it. Its mighty gravity commands planets to orbit and pulls comets into it.
The sun is a main-sequence star, meaning that it makes energy by fusing hydrogen into helium. Hydrogen accounts for more than 70% of the star’s mass, with trace amounts of oxygen, carbon, neon, nitrogen, iron and silicon.
To make energy, the star’s core heats up to millions of degrees Celsius. During this process, atomic nuclei fuse together to release vast amounts of heat and light in the form of X-rays, ultraviolet radiation, and infrared radiation.
This is an endless source of energy that is essential to life on Earth. It takes light from the sun eight minutes to reach Earth, and it travels at about 300,000 km per second.
The Sun’s interior is divided into a core, radiative zone and convective zone. Above that, there’s the photosphere, chromosphere and transition zone.
In between these layers is the solar corona, an ionized layer of plasma that extends beyond the chromosphere into the sun’s atmosphere. This layer is so bright that it outshines all the other layers in the Sun’s atmosphere.
The solar wind, an outflow of matter from the solar corona, reaches a theoretical boundary called the heliopause at a distance of billions of kilometers from the sun. This boundary separates the solar system from the surrounding stars and the interstellar medium, which contains matter from other star systems. The solar wind eventually slows down at the heliopause, but it can carry away matter from other stars.
Our solar system is filled with many planets, satellites, and other objects. It is made up of Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune; five dwarf planets (Ceres, Pluto, Makemake, Haumea, and Eris); and more than 150 moons.
Our Solar System began about five billion years ago when a spinning cloud of gas and dust in the early universe collapsed to form the Sun. Collisions of materials in the surrounding nebula formed the eight planets that exist today, each with its own unique properties.
Between the inner and outer planets lies an area of space filled with millions of asteroids, small rocky, icy and metallic bodies left over from the formation of our Solar System. Astronomers theorize that the gravity of Jupiter shaped this region so much that no large planet could have formed there.
These asteroids are a source of information about the origins and evolution of our Solar System. They help us answer questions about our Solar System’s history, how it reached its diverse state, and how life might have evolved on Earth and possibly elsewhere in the solar system.
Several asteroids, such as Ceres and the Centaurs, may have originated in the original nebula but later moved to other parts of the Solar System. They are believed to be minimally altered from their initial conditions in the nebula, and they can give clues to the Solar System’s history and how it formed.
In addition, a group of detached minor planets, called the Kuiper belt, resides at a distance of about 9 billion miles from the Sun. Objects in this belt range in size from the tiny, ice-covered Ceres to Pluto’s huge moon Charon, which is the largest known asteroid. Some of these detached objects have been reclassified by the International Astronomical Union as dwarf planets.
The Oort Cloud
The Oort Cloud is the region of space surrounding the Sun where billions of icy planetesimals reside. It is much farther away from the Sun than the Kuiper Belt or the Scattered Disc, and it contains objects ranging in size from mountains to a few kilometers across.
During the formation of our Solar System, some of these icy bodies became trapped in an orbital shell surrounding the Sun, but they were eventually kicked out by the gravitational pull of incipient giant planets. Since then, these rocky remnants have accumulated in the Oort Cloud’s icy reaches.
One of the most intriguing discoveries about the Oort Cloud came in 2014 when the Kepler spacecraft observed a distant comet known as C/2013 A1 (Siding Spring). As it passed through K2’s field of view, scientists learned that its bright tail was actually made of water and carbon compounds left over from our Solar System’s early formation.
Scientists have found that some of these icy clumps can travel out of the Oort Cloud into interstellar space, where they become long-period comets. These comets are influenced by the gravity of passing stars, but they can also be pulled into the inner Solar System.
In addition, some of these icy objects are knocked out of their orbits when other stars pass by the Sun. This can then lead to their formation of long-period comets and even a few iceballs that get sent out into space.
The Oort Cloud is a mystery that will remain a part of our solar system’s history for as long as we continue to explore it. It is a place where astronomers still have yet to fully understand how long-period comets formed and why they travel so far from our Sun.
Spacecraft are vehicles that carry people and cargo beyond the Earth’s atmosphere, through space to other planetary bodies, space stations, or orbits, and back. They’re also used to explore space and communicate with other planets, moons, and asteroids in our Solar System.
A spacecraft can take many shapes and sizes, depending on its mission. Some are designed to study the environment on other planets, while others are used to gather data or provide communication services.
To send and receive communications, a spacecraft needs a communication system that can handle all incoming commands. The system uses a combination of dishes and antennas to transmit commands at various frequencies. The incoming messages are then processed by the command and data subsystem.
The system also receives ‘housekeeping’ information, called telemetry, which lets engineers on Earth monitor the condition of the spacecraft. In addition, the system generates electricity for the spacecraft by using radioisotope thermoelectric generators, which release heat when radioactive materials decay.
These probes have helped scientists learn more about our Solar System and its rocky planets, including Mars. They’ve also revealed evidence of water on some planets.
For these and other missions, scientists have had to design spacecraft that can withstand the harsh conditions of space, such as extreme thermal variation and radiation. They’ve also had to plan for occultations, which occur when the planet or the Sun shadows the spacecraft, cutting off its ability to produce energy.
These spacecraft have helped us unlock a lot of secrets about our Solar System, including how planets formed and evolved over time. We’ve also learned about the chemical composition of different planets and moons, and how they interact with their environments.
The Milky Way
The Milky Way is a large and complex galaxy that is home to billions of stars. It is surrounded by a halo of dark matter, which makes up about 90% of its mass.
It has two main parts: a disk, which contains the stars, and a bulge, which contains old, hot stars that are still forming new ones. The disk and bulge are both made of a mixture of stars, dust and gas, and they are held together by gravity.
Stars in the disk orbit around the center of the galaxy, forming swirling streams that appear to emanate like arms from the galactic bulge. Researchers are studying how these spiral arms form and disperse. They have found that the arms form in short periods of time, about 100 million years out of the galaxy’s 13 billion-year history.
Another interesting fact about the Milky Way is that it is not a flat disc, but a warped one. When it rotates, it precesses like a wobbling spinning top, a phenomenon that astronomers think may have been caused by a previous collision with a smaller galaxy.
In addition to the Milky Way itself, there are many other galaxies in our region of space. These include the Andromeda galaxy, which is accompanied by several dwarf companions. These are all part of a larger collection called the Local Group. They are also grouped within the Virgo Supercluster, which contains at least 100 galaxy groups and clusters.
In addition to these, there are thousands of globular clusters and stellar associations in the Milky Way’s plane that contain tens of thousands of stars. These clusters differ primarily in their age and number of stars.
The solar system started out as a cloud of gas and dust that cooled into a disk around a tiny star. Over millions of years, the Sun’s strong gravity pulled parts of the molecular cloud into clumps that became planets and asteroids.
A number of these rocky bodies remain in orbit around the Sun in elliptical paths that rotate counterclockwise. Others, such as Pluto and its moons Charon and Eris, are icy bodies that belong to the Kuiper belt.
The Sun is the center of our Solar System, responsible for its gravitational interactions with all eight planets and many smaller bodies. It is also the source of our light and heat, a crucial element for life on Earth.
Our Sun is a yellow dwarf star that formed around 4.6 billion years ago from the gravitational collapse of molecular matter in a cloud of gas. As the matter fell, the core became hot and dense enough to initiate nuclear fusion.
This process releases enormous amounts of energy through fusion reactions between hydrogen and helium. This energy is what makes our Sun the source of light and heat for the entire Solar System. Without this energy, no life on Earth would exist.
The Oort Cloud
The Oort Cloud is a thick bubble of distant, icy debris that encircles our sun. It’s a dense layer of objects that is believed to be the remnant of a protoplanetary disk that formed around our sun about 4.6 billion years ago.
The comets that make up the Oort cloud have come from two places: nearby parts of our solar system and other star systems in the outer reaches of our galaxy. They’ve been scattered from their initial accretion centers by the movements of planets and giant gas giants that were forming in this region at the time of our sun’s birth.
Researchers recently used sophisticated computer simulations to determine how the Oort Cloud formed. They found that gravitational interactions with nearby stars and galactic tides influenced cometary orbits to make them more circular.
The eight planets in the Solar System, ranging from Mercury to Neptune, orbit around the Sun. They are surrounded by rings of ice, dust and moons.
In the early days of our solar system, the rocky and icy bits left over from the original cloud of gas and dust were pulled in by gravity and began to clump together, eventually becoming planets. Some would become large enough to draw in smaller pieces, which eventually fell into orbit around them, becoming their moons.
Asteroids and comets were also part of this process. Many of them form a ring between Mars and Jupiter called the asteroid belt, which includes rocky objects from Ceres, which is classified by the IAU as a dwarf planet, to microscopic dust particles that are known as meteoroids.
The Dwarf Planets
In 2006, the International Astronomical Union (IAU) officially defined a new class of Solar System bodies called dwarf planets. Unlike Mercury and Venus, dwarf planets do not share orbital space with other objects; instead, they exist in a specialized zone of the Solar System.
The dwarf planets that are currently recognised by the IAU include Pluto, Eris, Makemake and Haumea. Several dozens more are under investigation by the scientific community.
In addition to these official dwarf planets, astronomers have discovered a number of other small, cold, trans-Neptunian objects with unusual shapes and/or properties. These include Gonggong, Quaoar and Sedna, among others.
Asteroids are small rocky remnants of the early formation of our solar system about 4.6 billion years ago. These chunks of space debris orbit the Sun between Mars and Jupiter.
The largest of these asteroids are Ceres, Vesta and Hygiea (all of which can be seen up close by asteroid-gazing spacecraft) but many smaller objects exist too. These rocks are thought to be the surviving remnants of battered planetesimals or fragments from larger bodies.
Asteroids are classified according to their location and composition. There are three broad composition classes: C-types (chondrites), S-types (stony) and M-types (metamorphic).