Some Notable Facts About Various Planets and Satellites

⇒ Mercury is the closest planet to the Sun.

⇒ It is extremely hot planet. It is visible two hours before sun rise.

⇒ Its special feature is the presence of magnetic field in it.

⇒ It is the smallest and lightest of all the planets. It has no moon.

⇒ The planet has no water on it.

⇒ Mercury planet has no gases like CO₂, N₂, H₂ and O₂ which can act as building blocks of life.

⇒ Mercury planet has no protective blanket like Ozone around it to prevent us from harmful radiations.

⇒ Venus is the second planet in distance from the Sun. This planet is nearest to the Earth and is also the brightest planet.

⇒ Venus is known as the ‘Evening Star’ as well as ‘Morning Star’.

⇒ Venus is surrounded by a thick cloud cover, hence known as the ‘Veiled Planet’ (‘veil’ means unclear/cover).

⇒ Venus is like the Earth in size and mass, and hence also known as the ‘Earth’s twin’. It also rotates clockwise like Uranus.

⇒ Venus is the hottest planet (even hotter than Mercury) of our Solar System, due to its veil of cloud.

⇒ Venus has no water on it. There is no sufficient oxygen on the Venus.

⇒ Earth is the largest of the inner planets and the fifth largest planet of our solar system.

⇒ The Earth is 23½° tilted on its axis and thus makes 66½° angle. The earth rotates by 1″ in 4 minutes.

⇒ It takes 23 hours 56 minutes and 4.091 seconds to rotate on its axis with a speed 1,610 km/h.

⇒ It takes 365 days, 5 hours and 48 minutes to revolve around the Sun. Mean velocity = 29.8 km/sec

⇒ The Earth is known as the ‘watery planet’ or the ‘blue planet’ due to the presence of huge amount of water on it.

⇒ The Earth is the only known planet which provides sustenance or life on it. It has a large quantity of oxygen which supports life.

⇒ The Moon is the only satellite of the Earth.

⇒ It has a diameter of 3,475 km and its circumference is 10,864 km while its orbit is elliptical.

⇒ The maximum distance (apogee) of the Moon from the Earth is 4,06,000 km, the minimum distance (perigee) is 3,64,000 km and approximate average distance is 3,84,400 km.

⇒ It takes 27 days, 7 hours and 43 minutes to rotate on its axis (this period of about 27½ days is called the sideral month) and approximately the same period of time it takes to revolve around the Earth. The Moon’s period of revolution with reference to the Sun is about 29.53 days (29 days, 12 hours, 44 minutes and 2.8 seconds). This period is called a synodic month.

⇒ Only 59% of the total surface of the Moon is visible from the Earth.

⇒ Mass (compared to that of the Earth) – 1:81.30

Density (relative to that of the water) – 3.34

Density (relative to that of the Earth) – 0.6058

Hidden part of Moon’s surface – 0.41 (41%)

Highest point on the Moon – Mt. Leibnitz (35,000ft.) situated on the South Pole of the Moon.

⇒ The bright part of the Moon is full of mountains whereas the dark patches are low lying plains.

⇒ ‘Sea of tranquility’ made of the plain of dust particles, is on the rear side of the Moon, which always remains dark.

⇒ The Moon has no atmosphere, no twilight and no sound.

⇒ The temperature during daytime is about 100°C and during night it drops down to about -180°C.

⇒ The light from the Moon takes 1.3 seconds to reach the Earth.

⇒ The size of the Moon is one-fourth (1/4th) the size of the Earth.

⇒ Gravitational pull of Moon is one-sixth (1/6th) that of the Earth.

⇒ Mainly silicon, iron, magnesium etc elements are found on the Moon’s surface.

⇒ The study of the Moon is called ‘Selenology’.

⇒ Moon is also known as the fossil planet.

⇒ Super Moons happen when a full Moon is closest to the Earth, appearing bigger and brighter than normal. They are called ‘super’ because they are 15% brighter and 30% bigger than regular full moons.

⇒ If in a calendar month there are two full moons then the second full moon is referred as Blue Moon. It is because of the gap between the two moons which is less than 31 days. If in any specific year Blue Moon appears in two or more than two months then it is referred as Blue Moon Year.

⇒ A ‘Blood Moon’ is the name given for a view of the Moon during a total lunar eclipse. Because of the way light passes through the Earth’s atmosphere during an eclipse, red light from the Sun is reflected on to it. The Moon’s reddish colour earns it the nickname-“Blood Moon”.

⇒ A sequence of four total lunar eclipses including no partial eclipses is called a tetrad.

⇒ On 22nd October, 2008 Indian Space Research Organization (ISRO) has successfully established CHANDRAYAAN-1 in the moon’s orbit from Satish Dhawan Space Centre in Sri Harikota of Andhra Pradesh by polar satellite launch vehicle PSLV-C-1.

⇒ In this project India manufactured unmanned space vehicle moon impact probe which has been landed on moon’s surface. Chandrayaan- 1, is first satellite with its own type with high resolution remote sensing facility with which images of moon could be seen, having 11 extra modern apparatus including X-ray, spectrometer, miniature synthetic aperture radar, moon mineralogy mapper (M-3) etc. This takes pictures of moon’s surface even of the whole of its chemical environment and provides information about its soil, mineral, ice, heat and weather etc.

⇒ India’s Geosynchronous Satellite Launch Vehicle, GSLV MKIII-M1, successfully launched Chandrayaan-2 spacecraft on July 22, 2019 into its planned orbit with a perigee (nearest point to Earth) of 169.7 km and an apogee (farthest point to Earth) of 45,475 km. The launch took place from the Second Launch Pad at Satish Dhawan Space Centre, SHAR Sriharikota.

⇒ Chandrayaan-2 mission comprised an Orbiter, Lander and Rover to explore the unexplored South Pole of the Moon.

⇒ After the injection of Chandrayaan-2, a series of maneuvers were carried out to raise its orbit and on August 14, 2019, following Trans Lunar Insertion (TLI) maneuver, the spacecraft escaped from orbiting the earth and followed a path that took it to the vicinity of the Moon. On August 20, 2019, Chandrayaan-2 was successfully inserted into lunar orbit. While orbiting the moon in a 100 km lunar polar orbit, on September 02, 2019, Vikram Lander was separated from the Orbiter in preparation for landing. Subsequently, two de-orbit maneuvers were performed on Vikram Lander so as to change its orbit and begin circling the moon in a 100 km × 35 km orbit. Vikram Lander descent was as planned and normal performance was observed up to an altitude of 2.1 km. Subsequently communication from lander to the ground stations was lost.

⇒ But the Orbiter camera is the highest resolution camera (0.3 m) in any lunar mission so far and will provide high resolution images which will be immensely useful to the global scientific community.

⇒ Iron-rich red soil and pink sky of Mars give it the name, ‘Red Planet’.

⇒ Mars has a cold desert world. It is half the size of Earth. Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons and weather. It has an atmosphere made of carbon dioxide, nitrogen and argon.

⇒ Mars is a terrestrial planet. It is small and rocky. Mars has a thin atmosphere. Mars has an active atmosphere, but the surface of the planes is not active. Its volcanoes are dead.

⇒ One day on Mars lasts 24.6 hrs. It is just a little longer than a day on the Earth. One year on Mars’s is 687 Earth days. It is almost twice as long as one year on the Earth.

⇒ Mars has two moons. Their names are Phobos and Deimos. Mars is the fourth planet from the Sun. That means Earth and Jupiter are Mars’s neighbouring planets.

⇒ Mars Orbiter Mission (MOM), the maiden interplanetary mission of ISRO, launched on November 5, 2013 by PSLV-C25 got inserted into Martian orbit on September 24, 2014 in its first attempt.MOM completes 1000 Earth days corresponds to 973.24 Mars Sols (Martian Solar Day) and MOM completed 388 orbits.

⇒ Jupiter is the largest planet of the Solar System.

⇒ Jupiter is also known as winter planet as its average temperature is very low (-148° C).

⇒ Ganymede, (yellow in colour), largest satellite of Jupiter is the also largest satellite in the Solar System.

⇒ Saturn is the second largest planet in the Solar System.

⇒ Saturn has bright concentric rings which are made up of ice and ice-covered dust particles which revolve around it.

⇒ Titan is the largest satellite of Saturn.

⇒ Uranus is about four times the size of the Earth. This planet appears greenish in colour because of methane gas present in its atmosphere.

⇒ Uranus was discovered in 1781 by Sir William Herschel.

⇒ Uranus is the 7th planet from the Sun.

⇒ Uranus is the first planet to have been discovered by the use of a telescope.

⇒ Uranus is the third largest planet of the Solar System.

⇒ Uranus is extremely cold, having surface temperature (-) 190°C and is surrounded by 13 rings namely zeta (ζ)/R1986U2, 6, 5, 4, alpha (α), beta (β), eta (ε), gamma (γ), delta (δ), lambda (λ), epsilon (∈), nu (ν) and mu (μ).

⇒ Uranus rotates from east to west on its axis, which is opposite to other planets except Venus.

⇒ The axis of Uranus has large inclination so that it appears to be lying down, hence it bears the name ‘A Planet on its Side’.

⇒ Neptune is the 8th (farthest) planet of the Solar System. The temperature on the surface of Neptune remains low.

⇒ Neptune is very similar to Uranus and can be considered as its twin.

⇒ Neptune is surrounded by methane rings of sub zero temperature.

⇒ On the basis of the new definition of planet given by the IAU (International Astronomical Union), the world’s top institution on space science research, leading astronomers participating in IAU’s meet at Prague (Czech Republic) on August 24, 2006, declared that Pluto would no longer remain a planet.

⇒ Under the IAU’s new guidelines, the number of planets in the Solar System has thus been reduced from nine to eight. Its merits mentioning here that, prior to this decision, Pluto had been holding the planetary status since its discovery in 1930 by Clyde Tombaugh.

⇒ Now, with the omission of Pluto from the Solar System, its membership has been restricted to the eight ‘classical’ planets, namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Weeks after it was demoted to a sub-planetary status, Pluto was given a new name to reflect its new status as a dwarf planet in September, 2006. The former 9th planet was assigned the asteroid number 134340 by the Minor Planet Centre (MPC), the official organization responsible for collecting data about asteroids and comets in our Solar System.

Pluto’s companion satellites, Charon (Pluto’s largest moon), Nix and Hydra are considered part of the same system and will not be assigned separate asteroid numbers. Instead, they will now be called 134340 I, II and III respectively.

⇒ Asteroids are also known as minor planets. They are objects that revolve around the Sun.

⇒ They are mostly found between the orbits of Mars and Jupiter. They are a belt of debris which failed to assemble into planets and keeps on revolving around the Sun. This has come to be called as ‘asteroid belt’.

⇒ More than 5000 asteroids have been identified. Asteroids may be spherical, elongated or irregular in shape.

⇒ All asteroids rotate on their axis, every 5 to 20 hours. Certain asteroids may have satellites.

⇒ Trojan asteroids are found in two clouds moving in the orbit of Jupiter, one moving ahead of it and the other moving behind it.

⇒ Scientists believe that these asteroids occupy a place where a planet could have existed but was prevented from its formation by the disruptive gravitational force of the nearby giant planet, Jupiter.

⇒ Meteors and Meteorites are also called shooting stars.

⇒ Meteors are fragments of rocks coming towards the earth, formed due to the collision of asteroids with one another.

⇒ Meteors are usually small, and due to the heat produced by air resistance, burn up before they reach the Earth’s surface.

⇒ When meteors are large and do not burn up completely, they land on the Earth’s surface and are known as Meteorites.

⇒ All meteorites are believed to originate in the asteroid belt, where a sudden collision may send them towards the Earth and the Earth’s gravity attracts them towards its surface.

⇒ Visitors of the Solar System, Comets (the name derived from the Latin words stella cometa meaning ‘hairy star’) are among the most spectacular and unpredictable bodies in the Solar System.

⇒ Comets move around the Sun in regular orbits, but their orbits are elongated ellipses that it takes them hundreds and, sometimes even thousands of years to complete one revolution around the Sun.

⇒ Comets are made up of frozen gases which hold together rocky and metallic materials.

⇒ A comet becomes visible only when it travels close to the Sun. Its ice melts and the gas and dust is swept back into a tail.

⇒ The tail always points away from the Sun. So when it is travelling away from the Sun it is led by its tail.

⇒ A comet is characterised by a long luminous tail, which emits light. But, this is visible only when the comet’s orbit passes close to the Sun.

⇒ When the comet travels close to the Sun, the ice melts to a head of gas called a Coma. The Sun’s radiation sweeps this into a gas tail. Dust particles are also swept back to form a dust tail.

⇒ Stars are heavenly bodies made up of hot burning gases, thus shining by their own light.

⇒ Stars seem to be fixed with respect to each other. In fact they are in rapid motion but they are at such great distance that relative changes in position become noticeable only over the centuries.

⇒ According to NASA Proxima Centauri is the closest star to the Earth after the Sun. It is about 4.24 light years away.

⇒ Pole star (or Polaris), Sirius, Vega, Capella, Alpha centauri, Beta centauri, Proxima centauri, Spica, Regulus, Pleiades, Aldebaran, Arcturus, Betelgeuse, and of course the Sun are some of the important examples of the stars.

⇒ There are billions and billions of stars in the sky but only about 2000 stars can be seen with the naked eye on a clear moonless night.

⇒ There are 1022 stars in the Universe.

⇒ About 8000 stars are visible from the Earth with naked eye. Out of this, 4000 stars are visible in the Northern Hemisphere and 4000 in the Southern Hemisphere.

⇒ In either hemisphere, only 2000 stars are visible at any given time. The other 2000 are located in the day-time sky and the brightness of the Sun renders them invisible.

⇒ To enable astronomers to identify roughly the position of the stars, the sky has been divided into units. These units are known as Constellations.

⇒ These constellations were named in the honour of mythological characters.

⇒ At present 88 constellations are recognized.

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