The Solar System
The solar system is a family of Sun consisting of eight major planets, one dwarf planet (Pluto), satellites, asteroids, Moons, meteors, and comets. All these orbits the sun to form Solar System.
Sun is our motherly and nearest star, that creates energy from nuclear reactions deep within the interior, by its light and heat life is possible on Earth.
Origin of Solar System:
The solar system formed 4.6 (4.568) billion years ago from the gravitational collapse of a giant interstellar molecular cloud.
- Bodies close to the sun i.e. the terrestrial planets were formed from rocks and metals that crystallized at high temperatures.
- Outer planets were formed by solid condensed elements at low temperatures.
- Most scientists believe that the universe began about 15 billion years ago through Big Bang, a gigantic explosion.
- Sun is a yellow dwarf (G2 type main sequence) star, a hot ball of glowing gases.
- The Sun is the largest object in our solar system, comprising 99.8% of the system’s mass, with a diameter of 1,392,00 km (864,948 miles)
- The gravity of the Sun holds the solar system together, keeping everything from the biggest planets to the smallest particles of debris in its orbit.
- The core of the Sun: is considered to extend from the center to about 0.2 to 0.25 of the solar radius. It is the hottest part of the Sun and of the Solar System. It has a density of 150 g/cm3 at the center, and a temperature of 15 million kelvins, sustain nuclear fusion of Hydrogen into Helium.
- Electric currents in the Sun generate a magnetic field that is carried out through the solar system by the solar wind – a stream of electrically charged gas blowing outward from the Sun in all directions.
- Earth orbits the Sun from a distance of about 93 million miles. The connection and interactions between the Sun and Earth drive our planet’s seasons, ocean currents, weather, climate, radiation belts, and aurorae.
- Photosphere: The brightest outer layer of the Sun is Photosphere, which emits radiation, visible lights. It consists zone of burning gases, it is the extremely uneven surface with the temperature at the outer side is 6000° K.
- Chromosphere: a relatively thin layer of burning gases just above the photosphere is called the Chromosphere.
Sunspot: It is a dark patch on the surface of the Sun. These patches appear as they are about 1500° Celsius cooler than the surrounding chromosphere.
- Each sunspot consists black center or umbra and a lighter region or penumbra.
These are celestial bodies moving in an elliptical orbit around a star. Currently, eight planets are orbiting our star Sun.
The inner, rocky planets are Mercury, Venus, Earth, and Mars and also comprise the asteroid belt.
- (NASA’s newest rover — Perseverance — landed on Mars on Feb. 18, 2021.)
The outer planets are gas giants Jupiter and Saturn, and Ice giants Uranus and Neptune.
The Inner Planets:
Mercury: (God of commerce and skill)
The smallest planet in our solar system and nearest to the Sun, Mercury is only slightly larger than Earth’s Moon
- Mercury – God of commerce and skill
- Diameter- 4878 km, (3,03miles)
- Mass- approx. 3.30 *10power 20 tonnes.
- Density- 5.43 g/cm3
- Distance from the sun- 58 million km
- Surface gravity-1kg = 0.88kg
- Length of year- 87.97 Earth day
- Length of Day- 58.65 Earth day
- Mercury is the fastest planet in our solar system – traveling through space at nearly 29 miles (47 kilometers) per second.
- it has the shortest year of all the planets in our solar system – 88 days.
- Mercury is a rocky planet, also known as a terrestrial planet. Mercury has a solid, cratered surface, much like the Earth’s moon.
- Mercury’s thin atmosphere, or exosphere, is composed mostly of oxygen (O2), sodium (Na), hydrogen (H2), helium (He), and potassium (K).
- Mercury has no moons.
NASA mission on Mercury: Two NASA missions have explored Mercury: Mariner 10 was the first to fly by Mercury, and MESSENGER was the first to orbit. ESA’s BepiColombo is on its way to Mercury.
Venus- (The Veiled Planet, Goddess of Beauty):
Venus is the second planet from the Sun and is Earth’s closest planetary neighbour.
- Diameter: 12,102 km
- Mass: 4.867 × 10^24 kg (0.815 M⊕)
- Length of Year: 224.7 Earth day
- Length of day: 243.01 Earth Day
- It’s one of the four inner, terrestrial (or rocky) planets, and it’s often called Earth’s twin because it’s similar in size and density.
- The Planet has a thick, toxic atmosphere filled with carbon dioxide, Thick yellowish cloud of sulphuric acid traps heat, causing the greenhouse effect
- It’s the hottest planet in our solar system, even though Mercury is closer to the Sun.
- Surface temperatures on Venus are about 900 degrees Fahrenheit (475 degrees Celsius) – hot enough to melt lead.
- Venus has high plateaus, folded mountains, and numerous volcanos.
- Another big difference from Earth – Venus rotates on its axis backward, compared to most of the other planets in the solar system.
- On Venus, the Sun rises in the west and sets in the east, opposite to what we experience on Earth.
- Venus was the first planet explored by a spacecraft- NASA’s Mariner 2 Successfully on 14 Dec. 1962. Since then numerous spacecraft from the U.S and other space agencies have explored Venus.
- NASA’s Magellan mapped the planet’s surface with radar.
- More recent Venus missions include ESA’s Venus Express (which orbited from 2006 until 2016) and Japan’s Akatsuki Venus Climate Orbiter (orbiting since 2016).
Earth is our home planet, the third planet from the Sun, and the only place we know that’s inhabited by livings.
- Diameter: 12,756 km
- Radius: 6,371 km
- Mass: 5.972 × 10^24 kg
- Length of Day: 23.92 hours
- Length of year: 365. 25 Earth days
- Distance from sun: 93 million miles (150 million km)
- Earth is the third planet from the Sun
- Earth is the fifth largest planet.
- The planet is unique as the only planet in the solar system with liquid water on the surface.
- Earth is the largest and densest of inner planets.
- All of the planets, except for Earth, were named after Greek and Roman gods and goddesses. However, the name Earth is a Germanic word, which simply means “the ground.”
- Earth’s atmosphere is 78 percent nitrogen, 21 percent oxygen, and 1 percent other ingredients—the perfect balance to breathe and live.
- Earth has one moon.
- The atmosphere of Earth protects us from incoming meteoroids, most of which break up in our atmosphere before they can strike the surface.
Mars (Red Planet, God of war):
Mars is a Dusty, cold, desert world with a very thin atmosphere. There is strong evidence Mars was—billions of years ago—wetter and warmer, with a thicker atmosphere.
- Diameter- 6,786km
- Mass- 6.39 × 10^23 kg (0.107 M⊕)
- Distance from the sun- 228milliom km
- Length of the day- 24.623 hours
- Length of year- 188 Earth day
- Mars is the fourth planet from the Sun – a dusty, cold, desert world with a very thin atmosphere. Mars is also a dynamic planet with seasons, polar ice caps, canyons, extinct volcanoes, and evidence that it was even more active in the past.
- Mars has two small moons, Phobos and Deimos
- Mars has a thin atmosphere made up mostly of carbon dioxide, nitrogen, and argon gases
- The reason Mars looks reddish is due to oxidization – or rusting – of iron in the rocks, regolith (Martian “soil”), and dust of Mars. This dust gets kicked up into the atmosphere and from a distance makes the planet appear mostly red.
- NASA currently has two rovers (Curiosity and Perseverance), one lander (InSight), and one helicopter (Ingenuity) exploring the surface of Mars.
- Perseverance is one of three spacecraft that arrived at Mars in 2021.
- The Hope orbiter from the United Arab Emirates arrived on Feb. 9, 2021.
- China’s Tianwen-1 mission arrived on Feb. 10, 2021, and includes an orbiter, a lander, and a rover.
- Europe and India also have spacecraft studying Mars from orbit.
The Outer Planets:
Jupiter (Giant Planet, Ruler of Gods):
Jupiter is the fifth planet from our Sun and is, by far, the largest planet in the solar system.
- Diameter- 142.984 km
- Mass- 1.898 × 10^27 kg (317.8 M⊕)
- Distance from Sun- 778 million km
- Length of day- 9.84 hours
- Length of year- 11.86
- Jupiter’s stripes and swirls are actually cold, windy clouds of ammonia and water, floating in an atmosphere of hydrogen and helium
- Jupiter has dozens of moons, several faint rings made of dust. It consists four large moons and many smaller moons, it has 53 confirmed.
- The four moons – Io, Europa, Ganymede, and Callisto—were first observed by the astronomer Galileo Galilei in 1610 using an early version of the telescope
- Ganymede is the largest moon in the solar system (even bigger than the planet Mercury).
- Jupiter has the shortest day in the solar system.
- The composition of Jupiter is similar to that of the Sun—mostly hydrogen and helium. Deep in the atmosphere, pressure and temperature increase, compressing the hydrogen gas into a liquid.
Saturn (Ringed Planet, God of Agriculture):
Saturn is the sixth planet from the Sun and the second-largest planet in our solar system.
- Diameter- 120,660 km
- Mass: 5.683 × 10^26 kg (95.16 M⊕)
- Distance from Sun- 1,427 million km
- Length of the day- 10.23 hours, Saturn has the second-shortest day in the solar system
- Length of year- 29.46 earth
- Saturn is a massive ball made mostly of hydrogen and helium.
- Saturn is the only planet in our solar system with an average density that is less than water.
- It is a gas giant; Saturn doesn’t have a true surface.
Rings of Saturn:
Currently, Saturn has 53 confirmed moons with 29 additional provisional moons awaiting confirmation.
- Saturn’s rings are thought to be pieces of comets, asteroids, or shattered moons that broke up before they reached the planet, torn apart by Saturn’s powerful gravity.
- Saturn’s ring system extends up to 175,000 miles (282,000 kilometers) from the planet, yet the vertical height is typically about 30 feet (10 meters) in the main rings.
- The rings are named alphabetically, the main rings are A, B, and C. Rings D, E, F, and G are fainter and more recently discovered.
Uranus (The green Planet, God of Heavens):
Uranus is the seventh planet from the Sun, with the third largest diameter in our solar system. It was the first planet found with the aid of a telescope, in 1781 by astronomer William Herschel.
- Diameter- 2300km
- Mass- (8.6810±0.0013) ×1025 kg
- Distance from Sun- 2,870 million km
- length of day- 17.9 hours
- Length of year- 84.01 years
- Uranus has 27 known moons, Uranus’ moons are unique in being named for characters from the works of William Shakespeare and Alexander Pope.
- Most (80% or more) of the planet’s mass is made up of a hot dense fluid of “icy” materials – water, methane, and ammonia – above a small rocky core.
- Uranus’ atmosphere is mostly hydrogen and helium, with a small amount of methane and traces of water and ammonia
- Its blue-green colour is due to methane gas in the atmosphere.
- Inner moons appear to be roughly half water ice and half rock. The composition of outer moons is unknown, they have likely captured asteroids.
- Uranus consists of two sets of rings, nine rings in the inner system, and two outer rings.
- In order of increasing distance from the planet, the rings are called Zeta, 6, 5, 4, Alpha, Beta, Eta, Gamma, Delta, Lambda, Epsilon, Nu, and Mu. Some of the larger rings are surrounded by belts of fine dust
Neptune (A twin, God of Sea):
Neptune is the eighth planet from Sun and the only planet in our solar system not visible to the naked eye and the first predicted by mathematics before its discovery. In 2011 Neptune completed its first 165-year orbit since its discovery in 1846. (Source NASA)
NASA’s Voyager 2 is the only spacecraft to have visited Neptune up close.
- Diameter: 49,528 km
- Mass: 10.024*10^26 kg
- Distance from Sun: 4,497 million km
- Length of day: 16 hours
- Length of year: 14.79 Earth year.
- Neptune is about four times wider than Earth
- Neptune is an ice giant. Most of its mass is a hot, dense fluid of “icy” materials – water, methane, and ammonia – above a small rocky core.
- Neptune’s atmosphere is made up mostly of molecular hydrogen, atomic helium, and methane
- Neptune has 14 known moons.
Pluto: Pluto is a Dwarf planet that lies in the Kuiper Belt.
- Diameter – 1,400 miles (2,380 km) wide.
- Distance from Sun- 5,900 million km
- Length of the Day- 6.39 hours
- Length of year- 248.54cearth years.
- Pluto has a thin atmosphere of nitrogen, methane, and carbon monoxide
- On 24 August 2006, The International Astronomical Union (IAU) meeting held in Prag downgraded the status of Pluto to a dwarf planet.
Dwarf planet Ceres is the largest object in the asteroid belt between Mars and Jupiter, and it’s the only dwarf planet located in the inner solar system.
It is also located in the Kuiper Belt, a donut-shaped region of icy bodies beyond the orbit of Neptune.
Originally designated 2003 EL61 (and nicknamed Santa by one discovery team), located in Kuiper Belt. It is the roughly same size as Pluto. It is one of the fastest rotating large objects in our solar system.
- The moons of Haumea are discovered in 2005.
- In 2008, Haumea was recognized as a dwarf planet by IAU.
Moons are also known as natural satellites. These orbit planets and asteroids in our solar system.
- Earth has one moon.
- More than 200 moons in our solar system.
Also called minor planets. These are rocky, airless remnants left over from the early formation of the Solar system. Current known Asteroids are 1,113,527.
These are mostly irregular in shape, few are spherical, often pitted or cratered. Asteroids revolve around the sun in elliptical orbits, which brings them near to Sun and into the inner solar system.
There are three broad composition classes of asteroids are C-, S-, and M-types.
Comets are frozen leftovers from the formation of the solar system composed of dust, rock, and ices.
They range from a few miles to tens of miles wide, but as they orbit closer to the Sun, they heat up and spew gases and dust into a glowing head that can be larger than a planet. This material forms a tail that stretches millions of miles.
Currently the number of known comets- 3, 743.
The objects in space range in size from dust grains to small asteroids.
When meteoroids enter Earth’s atmosphere (or another planet) at high speed and burn up, the fireballs are called meteors.
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