Category Science & Technology

PLUTO

Pluto is the smallest, coldest and outermost planet in the Solar System. It was the last to be discovered, identified in 1930 by the American astronomer Clyde Tombaugh. He compared photographs of part of the sky taken six days apart and noticed that a pinprick of light had moved slightly against the background of stars. Pluto was the only outer planet not visited by Voyager 2, so astronomers still know little about it. Some even propose that Pluto is really a comet and not a planet at all.

Pluto has a very elongated orbit, ranging between 7400 and 4400 million kilometres from the Sun, bringing it inside the orbit of Neptune for part of the journey. Pluto’s moon, Charon, is just over half its size and lies only 19,640 kilometres away from it. Both spin in a direction opposite to that of the other planets except Venus.

Pluto is denser than the icy moons of Uranus and Neptune, suggesting that it has relatively large, rocky core.

Pluto’s surface is probably an “icescape” of frozen nitrogen, carbon monoxide and methane. There may be craters made by collisions with rock and ice fragments. Seen from Pluto, the Sun looks no more than a bright, distant star. It still provides just enough heat to evaporate some of the surface frost and create an extremely thin atmosphere. Charon, Pluto’s nearby moon, features prominently in the sky.

Thousands of icy objects may exist in the outer reaches of the Solar System. They may form either a belt or a cloud. This could be the birthplace of comets.

Picture Credit : Google

NEPTUNE

Neptune was discovered by German astronomer Johann Galle in 1846. Its largest moon, Triton, was recorded a few days later. Besides that, very little was known about Neptune until the space probe Voyager 2 visited it in 1989.

A bright blue globe, Neptune almost completely lacks surface features. At the time it was photographed by Voyager, a storm system, called the Great Dark Spot (which later disappeared), could be seen racing in a direction opposite to the planet’s rotation. Winds on Neptune blow at more than 2000 kilometres per hour.

Like the other gas giants, Neptune has a system of rings. There are four extremely faint rings, composed of dark, icy fragments.

VOYAGER 2

The greatest journey by a space probe so far undertaken was made by Voyager 2. Between 1979 and 1989, it flew close by Jupiter, Saturn, Uranus and Neptune, transmitting superbly clear pictures of the planets and their moons. Voyager has since sped away from the Solar System, although it continues to send back signals – 20 billion times weaker than those of a watch battery!

Voyager is playing its part in the search for life in other solar systems. Should aliens ever come across the space probe they will find an audiovisual disc on board. If they play it, they will hear, among other things, the sounds of whales, baby crying and greetings in 55 languages.

Picture Credit : Google

URANUS

Uranus was discovered in 1781 by William Herschel, an amateur German astronomer living in England. More recently, astronomers found that Uranus is tilted 98° from the vertical, meaning that it orbits the Sun almost on its side. So for much of the 84-year-long journey, both poles face long periods of continuous daylight, followed by continuous night.

            Uranus’ relatively small, rocky core is surrounded by a slushy ocean of water with some ammonia. Its thick atmosphere is composed mainly of hydrogen.

            Uranus has a family of 11 faint rings, none more than 10 km wide, each made up of pitch-black blocks, measuring only a few metres deep. They circle Uranus’ equator.

Picture Credit : Google

MARS

Although Mars is much smaller than Earth, the two planets have a number of similarities. The Martian day is only a little longer than ours and its angle of tilt means that Mars has four seasons, just as we do on Earth. Daytime temperatures at the equator in midsummer can sometimes reach 25°C. Thin clouds of water vapour or early morning surface frosts can also sometimes be seen. Like Earth, Mars has volcanoes, mountains, dried-up river beds, canyons, deserts and polar icecaps.

For these reasons, Mars is thought to be the only other planet where life may once have existed. However, analysis of the Martian soil by space probes Viking 1 and 2, which touched down on the planet in 1976, and Pathfinder in 1997, failed to find any sign of past or present life.

Mars is a barren planet. Its reddish colour comes from iron oxide dust (similar to rust). From time to time, large dark regions appear on the surface. These are areas of bare rock, exposed when storms remove the dusty covering. The Martian landscape features some dramatic landforms. The Solar System’s highest mountains and its deepest canyon, Valles Marineris, are found on Mars.

Mars has quite a low density and a very weak magnetic field. This suggests that it has only a relatively small ball of iron at its core.

 A number of valleys and channels have been carved into the Martian plains. From the evidence of sediments – muds and silts deposited by water – it seems likely that there were once rivers, lakes and even seas on Mars. The only water left on the surface today is frozen in the polar icecaps. The rest may have been lost to space due to Mar’s weak gravity, or hidden from view as a deep-frozen layer beneath the surface.

Picture Credit : Google

MOON

The moon is neither a star nor a planet. It is a ball of rock that travels around Earth, taking about 27 days to complete the circle. It is the brightest object in the night sky, although the light it “shines” is reflected from the Sun.

The Moon may have formed when a large object or planetesimal collided with the newly-formed Earth more than four billion years ago. The impact “splashed” into space vast amounts of debris that later came together to form the Moon.

            A completely barren world, the Moon’s surface consists of cratered highlands and wide plains. The Moon’s internal structure is similar to Earth’s; its crust is thicker and not divided into tectonic plates.

            With neither air nor liquid water, it is impossible for plants or animals to live on the Moon. The barren lunar landscape is pitted with craters, blasted out by meteorites crashing to its surface. Scattered debris has left streaks radiating from some craters. The Moon also has wide, smooth lava plains. Early astronomers thought these were seas. They are still called by the Latin name for sea, mare.

PHASES OF THE MOON

The shape of the Moon appears to change from one night to the next. This happens because, as it travels round Earth, it spins only once, so the same face remains pointed towards us at all times. It is our view of the sunlit part that changes. When the face pointed towards us is turned away from the Sun, we cannot see the Moon at all: a New Moon (1).When it is turned towards the Sun, we see a complete disc: a Full Moon (5). In between, it passes through crescent (2), quarter (3) and gibbous (4) phases, and back again (6-8).

Picture Credit : Google

SATURN

All four gas giants have rings, but Saturn’s, visible from Earth through even a small telescope, are broad, bright and magnificent. As detailed photographs taken by Voyager 2 show, the rings are made up of billions of blocks of ice and rock, ranging in size from boulders as large as houses down to tiny fragments the size of snowflakes. They are only a few tens of metres thick. Some astronomers think that the rings are the fragmented remains of a moon that was smashed apart by a passing comet.

Three rings can be made out from Earth. The outer ring (A ring) is separated from the other two lying inside it (B and C) by a gap called the Cassini Division. Voyager 2 spotted fainter rings beyond A ring. It also revealed that each ring was, itself, divided into thousands of ringlets.

Saturn has a large family of moons, many of which are small, irregularly shaped bodies with some even sharing the same orbits.

Swirling clouds and storms can sometimes be seen as ripples on Saturn’s globe. Saturn rotates very quickly, producing a distinct bulge at its equator. It is the least dense of the planets: if a large enough bathtub could be found, Saturn would float in the water!

Picture Credit : Google