What Is Solar System 5 Points?

A solar system is a gravitationally bound set of objects that orbit around a central star. Our Solar System consists of our star, the Sun, and everything bound to it by gravity – the planets Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, dwarf planets such as Pluto, dozens of moons and millions of asteroids, comets and meteoroids.

The Solar System formed about 4.6 billion years ago from the gravitational collapse of a giant molecular cloud. The vast majority of the system’s mass is in the Sun, with most of the remaining mass contained in the giant planets Jupiter and Saturn. The four smaller inner planets, Mercury, Venus, Earth and Mars, also called the terrestrial planets, are primarily composed of rock and metal. The four outer planets, called the gas giants, are substantially more massive than the terrestrials. The two largest, Jupiter and Saturn, are composed mainly of hydrogen and helium.

Beyond the orbit of Neptune, the Solar System is populated by the Kuiper Belt and the scattered disc, linked populations of icy bodies such as dwarf planet Pluto and comet nuclei. A much larger but more distant population of icy objects, called the Oort cloud, is believed to exist. The Solar System itself resides well within an immense, flattened region of the Milky Way Galaxy called the Local Bubble.

Table of Contents

The Sun

The Sun is a yellow dwarf star and the center of our solar system. It is classified as a G-type main sequence star based on its spectral class. With a diameter of about 1.4 million km and a mass of 2×1030 kilograms, the Sun contains 99.8% of the total mass of the solar system (space.com).

The Sun is composed mainly of hydrogen (about 70%) and helium (about 28%). The remaining 2% consists of heavier elements like oxygen, carbon, neon, and iron. At its core, nuclear fusion converts hydrogen into helium, generating heat and radiation. The surface temperature of the Sun averages 5,778K (Science NASA).

As a main sequence star, the Sun generates energy from the fusion of hydrogen nuclei into helium, through a proton-proton chain reaction. This nuclear reaction in the core produces solar radiation, which includes visible light, ultraviolet rays, infrared waves and other forms of electromagnetic radiation. The sunlight supports almost all life on Earth via photosynthesis (nhm.ac.uk).

Due to its gravitational dominance, the Sun holds the solar system together, keeping everything from the biggest planets to the smallest particles of debris in its orbit. The Sun rotates faster at its equator than at its poles. At the equator, the Sun spins once about every 25 days, but at its poles the Sun rotates once on its axis every 36 Earth days (space.com).

The Planets

The planets in our solar system orbit the Sun. The four planets closest to the Sun – Mercury, Venus, Earth, and Mars – are called the terrestrial planets and are primarily composed of rock and metal. The four large planets farther from the Sun – Jupiter, Saturn, Uranus, and Neptune – are called the gas giants and are composed mainly of hydrogen, helium and other gases.

Mercury is the smallest planet in our solar system and the closest planet to the Sun. Mercury has a very thin atmosphere and is covered with craters like our moon. Venus is the second planet from the Sun and is the hottest planet due to its thick atmosphere trapping heat. Earth is the third planet from the Sun and the only planet known to harbor life. Mars is the fourth planet from the Sun and is known as the Red Planet due to iron oxide on its surface.

Jupiter is the fifth planet from the Sun and the largest planet in our solar system. Jupiter is a gas giant with swirling cloud bands and a giant red storm called the Great Red Spot. Saturn is the sixth planet from the Sun and known for its beautiful rings. Uranus is the seventh planet from the Sun and rotates on its side orbiting the Sun. Neptune is the eighth and farthest officially recognized planet from the Sun.

The planets orbit the Sun in elliptical orbits that are very close to being circular. The orbits of the planets are also all roughly in the same plane (called the ecliptic). As the planets orbit the Sun, they also rotate on their axis to produce day and night cycles.

Dwarf Planets

A dwarf planet is a planetary-mass object that orbits the Sun but is not considered a true planet because it has not cleared its neighboring region of other objects. Dwarf planets are massive enough to attain a nearly round shape due to their own gravity, but not large enough to dominate their orbit.

There are five recognized dwarf planets in the Solar System: Ceres, Pluto, Makemake, Haumea, and Eris. Ceres is located in the asteroid belt between Mars and Jupiter and is the only dwarf planet in the inner solar system. Pluto was originally classified as the ninth planet but was reclassified as a dwarf planet in 2006. It has a highly eccentric orbit that takes it inside the orbit of Neptune to around 30 AU from the Sun. Makemake, Haumea, and Eris reside in the Kuiper belt beyond Neptune, with highly inclined and eccentric orbits.

According to NASA, Eris is slightly larger than Pluto at 2,326 km in diameter compared to Pluto’s 2,377 km, making Eris the largest known dwarf planet (https://science.nasa.gov/dwarf-planets/). However, Pluto has a larger moon called Charon while Eris has a small moon called Dysnomia. Haumea is unique among dwarf planets for its rapid rotation causing it to have an elongated football shape. There may be over 100 dwarf planets in the Kuiper belt region beyond Neptune that have yet to be discovered (https://www.space.com/18584-dwarf-planets-solar-system-infographic.html).

Moons

A moon is defined as a natural satellite orbiting a planet or minor planet. Moons do not give off their own light and instead reflect light from the sun.

According to List of natural satellites, the number of moons orbiting each planet is:

Mercury and Venus have no moons.

Earth has 1 moon – the Moon.
Mars has 2 moons – Phobos and Deimos.
Jupiter has 79 confirmed moons including the 4 Galilean moons – Io, Europa, Ganymede and Callisto.

Saturn has 82 confirmed moons including Titan.
Uranus has 27 confirmed moons including Titania, Oberon, Umbriel, Ariel and Miranda.
Neptune has 14 confirmed moons including Triton.

In total, there are at least 297 confirmed moons orbiting the planets in our solar system, with more being discovered periodically.

Asteroids

Asteroids are rocky remnants from the early formation of our solar system about 4.6 billion years ago (https://science.nasa.gov/solar-system/asteroids/facts/). They orbit the Sun but are much smaller than planets. The majority of known asteroids are found in the asteroid belt, between the orbits of Mars and Jupiter. This belt contains between 1.1-1.9 million asteroids larger than 1 km in diameter (https://science.nasa.gov/solar-system/asteroids/).

The largest asteroid is Ceres, which is almost 1,000 km in diameter (https://researchmatters.in/sciqs/7-amazing-facts-about-asteroids). The four next largest asteroids are Vesta, Pallas, Hygiea, and Interamnia. These are over 500 km in diameter. Most asteroids are irregularly shaped, but the largest ones are spherical due to gravity. Asteroids are classified into different types based on their composition. The three main types are C-type, S-type, and M-type.

Some of the most well-known asteroids include 433 Eros, which was visited by the NEAR Shoemaker spacecraft in 2000, and 101955 Bennu, which is the target for the OSIRIS-REx sample return mission. There are also asteroids that make close approaches to Earth such as 99942 Apophis. In addition, asteroids have collided with Earth in the past, playing a major role in the extinction of the dinosaurs 65 million years ago.

Comets

Comets are small, icy objects that orbit the Sun. They are made up of dust, rock, ice, and frozen gases like methane, ammonia, and carbon dioxide. As a comet approaches the inner solar system, solar heating causes the ices in the nucleus to sublimate, creating a glowing coma and sometimes a tail. Ten Important Comet Facts

Some of the most famous comets include Halley’s Comet, which is visible from Earth about every 75 years, and Comet Hale-Bopp, which was visible to the naked eye for over 18 months in 1996-1997. Comet Shoemaker-Levy 9 collided with Jupiter in 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects. Comets: Facts

Formation

According to NASA, our solar system formed about 4.6 billion years ago from a dense cloud of interstellar gas and dust called a solar nebula (NASA – Solar System Formation). Gravity caused the nebula to collapse, forming the Sun at the center. The remaining gas and dust formed a disk around the protostar Sun. As dust particles collided, they stuck together, growing into larger and larger clumps that eventually formed the planets, moons, asteroids and other objects.

The rocky planets like Mercury, Venus, Earth and Mars formed closer to the Sun, where it was too hot for gases like hydrogen and helium to survive. The outer planets Jupiter, Saturn, Uranus and Neptune formed farther from the Sun where ices like methane and ammonia could condense, leading to their composition of gas and ice. There are various theories about the details of planet formation, such as core accretion and disk instability. Overall the solar nebula model provides the foundation for how the Sun, planets and other objects formed billions of years ago.

Exploration

The history of solar system exploration began in the early 1960s with the launch of the first spacecraft to another planet. According to the Timeline of Solar System exploration, the first successful flyby of another planet was by Mariner 2 which flew by Venus in 1962. Since then, numerous space agencies have sent spacecraft to explore every planet and many moons and asteroids in our solar system.

Some key milestones in solar system exploration include:

First flyby of Mars by Mariner 4 in 1965
First flyby of Jupiter by Pioneer 10 in 1973

First Mercury flyby by Mariner 10 in 1974
First landing on Mars by Viking 1 in 1976
First flyby of Saturn by Pioneer 11 in 1979

First flyby of Uranus by Voyager 2 in 1986
First flyby of Neptune by Voyager 2 in 1989
First landing on an asteroid by NEAR Shoemaker on Eros in 2001

First landing on Titan by Huygens probe in 2005
First spacecraft to orbit Mercury by MESSENGER in 2011
First landing on a comet by Philae on 67P in 2014

First flyby of Pluto by New Horizons in 2015

NASA has been at the forefront of solar system exploration, as described in the 50 Years of Solar System Exploration publication. Dozens of NASA missions have explored every planet and transformed our understanding of the solar system.

Key Facts

Here are some quick key facts about our solar system:

The solar system consists of the Sun and everything that orbits around it, including eight planets and their moons, dwarf planets, asteroids and comets. The Sun contains 99.8% of the solar system’s mass.NASA

The four inner planets are Mercury, Venus, Earth and Mars. The four outer planets are Jupiter, Saturn, Uranus and Neptune.Funkidslive

Earth is the only planet known to have an atmosphere containing free oxygen, oceans of water on its surface and, of course, life.

Jupiter and Saturn are gas giants composed mainly of hydrogen and helium. Uranus and Neptune are ice giants, with cores of rock and ice.

Pluto was reclassified as a dwarf planet in 2006, reducing the number of planets in our solar system to eight.

The solar system is located in the Milky Way galaxy, which contains over 200 billion stars. Our Sun is just one of those stars.

The distance between planets increases the further they are from the Sun. For example, Venus is just 25 million miles from the Sun, while Neptune is 30 times further at 2.8 billion miles.

Comets are frozen leftovers from the formation of the solar system composed mostly of dust, ice and small rocky particles. They usually orbit the Sun in highly elliptical orbits.