The Solar System
THE MOON
The Solar System
1. What is the Moon?
- The Moon is the only natural satellite of the Earth and the fifth largest moon in the Solar System. It is a quarter of the Earth’s magnitude and 1/81 of its mass.
- It is the brightest, largest and closest heavenly body in space to the planet Earth.
- The Moon does not have its light but reflects the light of the Sun.
2. How was the Moon formed?
- The moon may have been formed from fragments expelled into the orbit around Earth by a collision between Earth and a massive object.
- The large dark patches on the Moon that look like seas, are in fact lava which flows from the volcanoes.
3. How far is the Moon from the Earth?
- The Moon’s distance from the Earth is 4,06,740 kilometres when the Moon is in apogee and 3,56,410 kilometres when the Moon is in perigee.
- The mean distance between the Earth and the Moon is 3,84,400 kilometres.
4. Why does Moon change Shape?
- The Moon does not change shape but when the Moon revolves, the Sun shines and lights up different portions of the Moon every night.
- These different shapes of the Moon are called the phases of the Moon.
- There are five main phases mainly New, Crescent, Quarter, Gibbous and Full.
- The Moon revolves around the Earth in 27 days and it also spins on its axis in 27 days.
5. Is the Moon moving away from the Earth?
- The Moon is moving away from ‘the Earth at a rate of about 3.8 centimetres per year.
- This happens because of the principle of conservation of momentum in the Earth’s orbit.
- This will happen for 50 billion more years and then the orbit of the Moon around the Earth would be stable.
- At that time it will take about 47 days to complete one revolution around Earth as compared to 27.3 now.
ECLIPSES
1.What is Lunar Eclipse?
- Lunar Eclipse takes place when the Moon passes through some part of the Earth’s shadow.
- The shadow comprises two cone shaped components, one inside the other.
- The outer or the penumbral shadow is a region where the Earth blocks only part of the Sun’s rays from reaching the Moon, whereas the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon.
2.What is Solar Eclipse?
- A Solar Eclipse happens when the Moon is directly between the Sun and the Earth.
- If the Moon’s umbral shadow sweeps across Earth’s surface, then a total eclipse of the Sun is seen.
- Total Eclipses occur once every few years and lasts for just a few minutes.
- When only the Moon’s penumbral shadow strikes theEarth,then we see a Partial Eclipse.
MARS
1.What is the Red Planet?
- Mars was named after the Roman God of War.
- The surface of Mars is covered with iron rich soil which reacts with oxygen creating iron oxide, giving the planet a rusty red
look. - Hence, Mars is referred as the Red Planet Mars is the fourth planet from the Sun.
- It has a diameter of 6,787 km and its size is almost half of that of the Earth
2.Are there any moons of Mars?
- Phobos and Deminos are two irregular shaped moons of Mars.
- These might have been asteroids which could have been captured by its gravity.
- Astronomer Asaph Hall discovered both these moons in 1877.
3.Is there life on Mars?
- Astronomers claimed to have seen straight lines on the planet’s surface which they supposed to be irrigation channels.
- Others are of the opinion that life is not possible on Mars because there is no water and barely 1 percent atmospheric pressure.
The Solar System
JUPITER
1.What do you know about Jupiter?
- Jupiter is the largest planet in the solar system.
- Jupiter is the fifth planet from the Sun.
- Jupiter’s average distance from the Sun is 5.2 AU.
- When viewed from Earth, it is usually the
second brightest planet in the sky, after Venus. - The planet is named after Jupiter, the king of the Roman Gods.
2.Does Jupiter have rings?
- Yes, Jupiter does have faint, narrow rings.
- Unlike Saturn, which has bright ice rings, Jupiter has dark rings which are made up of dust and tiny pieces of rock.
- Jupiter’s rings were discovered by NASA’s Voyager 1 mission in 1980.
3.How many moons does Jupiter have?
- Jupiter has at least 63 known moons.
- The largest four are called lo, Europa, Ganymede, and Callisto.
- These four moons are called the Galilean satellites because they were first seen in 1610 by the astronomer Galileo Galilei.
- Ganymede is the largest moon in the Solar System, with a diameter of 3,260 miles.
SATURN
1.What do you know about Saturn?
- Saturn is the sixth planet from the Sun, and the second largest after Jupiter.
- Its atmosphere comprises of hydrogen and helium with a small rocky centre.
- Its day is 19 hours and 39 minutes long and it takes 29.5 earth years to revolve around the Sun.
2.What are the rings of Saturn like?
- Saturn is not the only planet with rings.
- Jupiter. Uranus and Neptune have rings, too.
- But Saturn’s rings are the biggest and brightest.
- Saturn’s rings are made of ice and rock These pieces vary in size.
- Some are as small as a grain of sand. Others are as large as a house.
- From laraway, Saturn looks like it has seven large rings.
- Each large ring is named for a letter of the alphabet.
- The rings were named in the order they were discovered.
- The first ring discovered was named the A ring, but it is not the ring closest to or farthest from Saturn.
- Each large ring is made up of many small rings.
- The small rings are sometimes called ringlets.
The Solar System
SATURN'S MOONS
1.What do you know about Saturn?
- Saturn is the sixth planet from the Sun, and the second largest after Jupiter.
- Its atmosphere comprises of hydrogen and helium with a small rocky centre.
- Its day is 19 hours and 39 minutes long and it takes 29.5 earth years to revolve around the Sun.
2.What are the rings of Saturn like?
- Saturn is not the only planet with rings.
- Jupiter. Uranus and Neptune have rings, too.
- But Saturn’s rings are the biggest and brightest.
- Saturn’s rings are made of ice and rock These pieces vary in size.
- Some are as small as a grain of sand. Others are as large as a house.
- From laraway, Saturn looks like it has seven large rings.
- Each large ring is named for a letter of the alphabet.
- The rings were named in the order they were discovered.
- The first ring discovered was named the A ring, but it is not the ring closest to or farthest from Saturn.
- Each large ring is made up of many small rings.
- The small rings are sometimes called ringlets.
URANUS
1.What do you know about Uranus?
- Uranus is the third largest planet of our Solar System. It was discovered in 1781.
- It is tiltled on its side, hence the poles
are warmer than the equator. - Uranus has 27 moons.
- The largest moons of Uranus are Oberon and Titania.
- Its day is 17 hours and 14 minutes long while its year lakes 84 Earth years.
- It is also encircled by 13 main rings.
2.Why does Uranus appear greenish-blue?
- Planets get their colour from what they are made of these composition, and Uranus is made mostly of hydrogen, helium and methane.
- Methane is what gives Uranus its the
color.
3.Which is the coldest planet?
- Despite not being the farthest planet from the Sun, Uranus is the coldest planet.
- The minimum temperature here can fall below – 220 degrees Celsius.
- It is colder than Neptune because Neptune has a large moon known as Triton which heats it up because of the tidal interactions between the moon and the planet.
NEPTUNE
1.What is Neptune like?
- Neptune was discovered by Johann Galle and Heinrich D’Arrest in 1846.
- It has six rings which circle the planet.
- Neptune is a very windy place.
- No other planet in the Solar Neptune is 16 hours, 6 minutes and 36 seconds while its System has winds that are as strong as Neptune’s.
- A day on years takes almost 165 Earth years.
2.How many moons does Neptune have?
- Neptune has 13 moons that we know of.
- Triton is the largest of Neptune’s moons.
- It was discovered just 17 days after Neptune itself was discovered.
- Triton measures 2700 km opposite direction of the planet’s rotation across.
- Triton is unusual because it orbits Neptune in the is the only large moon in the Solar System to do this.
3.What is the Great Dark Spot?
- The Great Dark Spot, similar to the Great Red Spot-on Jupiter, is the name of many dark spots on Neptune.
- Just like Jupiter’s storms they are formed because of storms on Neptune, but unlike Great Red Spot they disappear and form once every few years.
- Neptune has the strongest of winds observed on any of the planets which achieve speeds of up to 2,100 kmph around the Great Dark Spot.
The Solar System
PLUTO
1.Why is Pluto notconsidered as a planet?
A planet is a celestial body that
(a) Is in orbit around the Sun.
(b) Has sufficient mass for its sell- gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.
(c) Has cleared the neighbourhood around its orbit, Pluto is relatively round and orbits the Sun, but it does not meet the criteria because its orbit crosses. This is why Pluto is not considered a planet.
2.What is So Special about Pluto and its moon Charon?
- The special relationship that Pluto and its moon Charon have is that instead of Charon revolving aroundPluto, just as the moons of other planets do, both Pluto and Charon
revolve around a common point over the surface of Pluto. - Because of this, scientists have often thought of classifying Pluto and Charon as a binary planet system.
TRANS-NEPTUNIAN OBJECTS
1.What is a plutino?
- A plutino is a trans-Neptunian object that shares a 2:3 orbital resonance with Neptune.
- Since Pluto shares the same orbital resonance with Neptune, all the other trans-Neptunian object who have the same orbital resonance are named after Pluto.
- Almost a quarter of the Kuiper Belt Objects are plutinos.
2.What is a plutoid?
- Largest known trans-Neptunian objects (TNOS) A plutoid is a term for those dwarf planets which lie beyond the orbit of Neptune.
- The International Astronomical Union formally defined this term in 2008.
- Only four dwarf planets lying beyond Neptune – Pluto, Eris, Hanumea and
Makemake-fulfill the definition of being a plutoid as of 2011.
3.What is 90377 Sedna?
- 90377 Sedna is a trans-Neptunian object which is the farthest object in the Solar System after long-period comets.
- Its perihelion is 76 AU and aphelion is 937 AU.