Question

Discuss the formation of the solar system. List the planets of the solar system, discussing their properties, attributes, and missions that explored them.

Answer 1

Formation of solar system:-Scientists believe that the solar system was formed when a cloud of gas and dust in space was disturbed, maybe by the explosion of a nearby star (called a supernova). This explosion made waves in space which squeezed the cloud of gas and dust. Squeezing made the cloud start to collapse, as gravity pulled the gas and dust together, forming a solar nebula. Just like a dancer that spins faster as she pulls in her arms, the cloud began to spin as it collapsed. Eventually, the cloud grew hotter and denser in the center, with a disk of gas and dust surrounding it that was hot in the center but cool at the edges. As the disk got thinner and thinner, particles began to stick together and form clumps. Some clumps got bigger, as particles and small clumps stuck to them, eventually forming planets or moons . Near the center of the cloud, where planets like Earth formed, only rocky material could stand the great heat. Icy matter settled in the outer regions of the disk along with rocky material, where the giant planets like Jupiter formed. As the cloud continued to fall in, the center eventually got so hot that it became a star, the Sun, and blew most of the gas and dust of the new solar system with a strong stellar wind. By studying meteorites, which are thought to be left over from this early phase of the solar system, scientists have found that the solar system is about 4600 million years old.

Planets of solar system:-

Mercury:-Mercury is the smallest and innermost planet in the Solar System. Its orbit around the Sun takes 87.97 days, the shortest of all the planets in the Solar System. It is named after the Roman deity Mercury, the messenger of the gods.

• Mercury does not have any moons or rings.
• Mercury is the smallest planet.
• Mercury is the closest planet to the Sun.
• Your weight on Mercury would be 38% of your weight on Earth.
• A day on the surface of Mercury lasts 176 Earth days.
• A year on Mercury takes 88 Earth days.
• It’s not known who discovered Mercury.

the Mariner 10 and MESSENGER missions have been the only missions that have made close observations of Mercury.

Venus:-

Venus is the second planet from the Sun and the third brightest object in Earth's sky after the Sun and Moon. It is sometimes referred to as the sister planet to Earth, because their size and mass are so similar. Venus is also the closest planet to Earth. The surface of Venus is hidden by an opaque layer of clouds which are formed from sulphuric acid.The planet is named for Venus, the Roman goddess of love and beauty and is the second largest terrestrial planet.

In 1990, the Magellan spacecraft began orbiting Venus. In addition to performing radar mapping similar to that of Pioneer Venus, Magellan also undertook a more advanced radar imaging that gathered much finer details.

Mars:-Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System after Mercury. In English, Mars carries a name of the Roman god of war and is often referred to as the 'Red Planet'.The latter refers to the effect of the iron oxide prevalent on Mars' surface, which gives it a reddish appearance distinctive among the astronomical bodies visible to the naked eye.

Mariner4,viking 1,soviet mars 3,mangalyaan all these are the mission on mars by different countries.

Earth:-

Earth is the third planet from the Sun and is the largest of the terrestrial planets. The Earth is the only planet in our solar system not to be named after a Greek or Roman deity. The Earth was formed approximately 4.54 billion years ago and is the only known planet to support life.

• The Earth’s rotation is gradually slowing.
  This deceleration is happening almost imperceptibly, at approximately 17 milliseconds per hundred years, although the rate at which it occurs is not perfectly uniform. This has the effect of lengthening our days, but it happens so slowly that it could be as much as 140 million years before the length of a day will have increased to 25 hours.
• The Earth was once believed to be the centre of the universe.
  Due to the apparent movements of the Sun and planets in relation to their viewpoint, ancient scientists insisted that the Earth remained static, whilst other celestial bodies travelled in circular orbits around it. Eventually, the view that the Sun was at the centre of the universe was postulated by Copernicus, though this is also not the case.
• Earth has a powerful magnetic field.
  This phenomenon is caused by the nickel-iron core of the planet, coupled with its rapid rotation. This field protects the Earth from the effects of solar wind.
• There is only one natural satellite of the planet Earth.
  As a percentage of the size of the body it orbits, the Moon is the largest satellite of any planet in our solar system. In real terms, however, it is only the fifth largest natural satellite.
• Earth is the only planet not named after a god.
  The other seven planets in our solar system are all named after Roman gods or goddesses. Although only Mercury, Venus, Mars, Jupiter and Saturn were named during ancient times, because they were visible to the naked eye, the Roman method of naming planets was retained after the discovery of Uranus and Neptune.
• The Earth is the densest planet in the Solar System.
  This varies according to the part of the planet; for example, the metallic core is denser than the crust. The average density of the Earth is approximately 5.52 grams per cubic centimetre.

Jupiter:-

Jupiter is the fifth planet from our Sun and is, by far, the largest planet in the solar system – more than twice as massive as all the other planets combined. Jupiter's stripes and swirls are actually cold, windy clouds of ammonia and water, floating in an atmosphere of hydrogen and helium. Jupiter’s iconic Great Red Spot is a giant storm bigger than Earth that has raged for hundreds of years.

Jupiter is surrounded by dozens of moons. Jupiter also has several rings, but unlike the famous rings of Saturn, Jupiter’s rings are very faint and made of dust, not ice.

NASA's Juno spacecraft is currently studying the gas giant planet from orbit. The spacecraft, which arrived at Jupiter in July 2016, is the first to study the planet's mysterious, cloud-shrouded interior. Scientists also use the Earth-orbiting Hubble Space Telescope and ground-based telescopes to regularly check in on Jupiter.

Uranus:-

The seventh planet from the Sun with the third largest diameter in our solar system, Uranus is very cold and windy. The ice giant is surrounded by 13 faint rings and 27 small moons as it rotates at a nearly 90-degree angle from the plane of its orbit. This unique tilt makes Uranus appear to spin on its side, orbiting the Sun like a rolling ball.The first planet found with the aid of a telescope, Uranus was discovered in 1781 by astronomer William Herschel, although he originally thought it was either a comet or a star. It was two years later that the object was universally accepted as a new planet, in part because of observations by astronomer Johann Elert Bode.

Day
17 hours 14 minutes

Year
84 Earth years

Radius
15,759.2 miles | 25,362 kilometers

Planet Type
Ice Giant

Moons
27

The exploration of Uranus has, to date, been solely through telescopes and a lone probe by NASA's Voyager 2 spacecraft, which made its closest approach to Uranus on January 24, 1986. Voyager 2 discovered 10 moons, studied the planet's cold atmosphere, and examined its ring system, discovering two new rings.

Saturn:-Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius about nine times that of Earth. It has only one-eighth the average density of Earth; however, with its larger volume, Saturn is over 95 times more massive.

Day
10.7 hours

Year
29 Earth years

Radius
36,183.7 miles | 58,232 kilometers

Planet Type
Gas giant

Moons
53 confirmed | 29 provisional.

The previous flybys were helpful to scientists, but to really study Saturn, NASA sent the Cassini/Huygens mission, which arrived and went into orbit around Saturn in 2004. As part of its mission, the spacecraft delivered the Huygens probe to study Titan.

Neptune:-Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth, slightly more massive than its near-twin Uranus.

The exploration of Neptune has only begun with one spacecraft, Voyager 2 in 1989. As of February 2020 there are no approved future missions to visit the Neptunian system. NASA, ESA and also independent academic groups have proposed future scientific missions to visit Neptune.

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