To infinity and beyond! Ever since the ancient ages, the skies and all its splendour have been a great object of fascination for humankind. In the last few decades, we have made giant leaps in space exploration. We put a man on the moon and a rover on Mars. But the universe is as astonishingly vast and ever expanding and we are making new discoveries every day. But let us a learn all we know about the stars and the solar system.
You look up at the beautiful sky and see all the stars twinkling away. And the luminous moon with its dull glow. But did you know that stars don’t really twinkle, it’s actually an illusion? And the moon does not emit any light of its own, it only reflects light from the sun. Let us explore our galaxy and learn other such captivating facts about the moon and stars.
A galaxy is defined as a group of stars and dust bound together due to gravity. But this is an oversimplification. The Galaxy actually comprises of millions and millions of cosmic objects, other than moon and stars and is endless and enchanting. The galaxy that we are a part of is called the Milky Way. Viewed from earth the galaxy looks like a milky patch it the sky, thus earning it the name.
By a recent estimation, there are about 1011 galaxies in existence. And there are an estimated 1011 stars in every one of these galaxies. The closest galaxy to ours that we have discovered is the Andromeda Galaxy. It is some 2.5 million light-years away.
We are all familiar with stars. We see them in the nighttime as these tiny little twinkling objects. But in actuality stars are these humongous balls of gases (generally hydrogen and helium) that are held together by their own gravity generated at the centre of the star. They emit their own light. Nuclear reactions happening at the core of the star support them against their own gravitational pull. The unit we use to measure the distance between earth and these stars is light-years. This is because measuring such huge distances in kilometres or miles can get tedious. A light year is simply the distance light travels in one year.
As I am sure you are aware, the sun is nothing but a medium-sized star in our galaxy. The only reason its appearance is different to that of other stars is because of its proximity to earth. It looks larger and brighter to other stars because it is closer to us. Its located only 150 million km away, and in cosmic terms that is significantly nearby.
A group of stars forming a recognisable pattern or shape is called a constellation of stars. These are a group of connected stars that make unique shapes. Some of the most famous constellations in our Milky Way are
Ursa Major: Also known as the ‘Big Dipper’. It is situated near the north pole. Its name means the Great Bear. It is one of the most recognizable shapes in the sky.
Orion: Another very prominent constellation it is named after a hunter in the Greek mythology.
Cassiopeia: A constellation located in the northern sky named after a boastful and vain queen in Greek mythology again. This constellation is easily recognisable due to its distinct W shape.
The scientific name for this twinkling phenomenon is called stellar scintillation. As the light from these stars travels million and millions of light years, it travels in a straight line. However, once the light enters the earth’s atmosphere it bounces around in different directions due to air and its movements. So when we perceive this light the stars appear to be twinkling!
The moon is a natural satellite of earth. It revolves around the earth from west to east and completes one such revolution in about 29 ½ days. As we discussed earlier the moon does not generate any of its own light, It reflects the light of the sun.
If you have noticed the shape of the moon keeps changing every day. From a full moon to the extent that there is no moon once a month. This is known as the phases of the moon. In total there are 12 phases of the moon. The shape of the moon changes in our skies as per the sunlit portion of the moon as viewed from earth.
As I am sure you are of the tides that occur in the seas and oceans i.e. high tides and low tides. The tides are cyclic in nature. But would you believe me if I told you that tides are caused by the moon? This is true. Tides are caused by the gravitational pull of the moon that causes oceans to bulge out in the direction of the moon. And the pull of the earth towards the moon causes the bulge occurring in the opposite direction. Hence we have 2 tides in a day.
Our solar system came into existence approximately 4.6 billion years ago with a big bang. There are various astronomical objects in our solar system. The sun is at the centre keeping all the other objects in an elliptical orbit around it. Other than the eight planets of the solar system there are many other objects in the galaxy that are not so known. Let us explore a few of these enchanting objects.
(Source: Wikipedia)
These are also known as the ‘dirty snowballs’. They are cosmic objects of frozen gasses, rocks and dust. These are not the tiny objects you imagine them to be. They are the size of a small town (at least a few kilometres in area). When these comets come close to the sun, these comets heat up and spew dust and gasses into the atmosphere. This results in the comets having a tail which is called a coma. Comets usually have a highly elliptical orbit, which means their revolutions around the sun are several years long. They tend to make periodical appearances in the earth’s atmosphere. Perhaps the most famous comet identified by us is the Halley’s Comet which makes an appearance every 74 to 79 years. Its last sighting was in 1986 and its next expected appearance is predicted to be in 2061.
Asteroids are essentially smaller planets, earning them the name of ‘minor plants’ or even ‘planetoids’. They are rocky objects that orbit the sun but do not have air (i.e. an atmosphere). These asteroids are located in the vast space occurring between Mars and Jupiter called the asteroid belt. There are tens of thousands of these ancient space rubble located in this belt, with sizes ranging from 945 kilometres to about 33 feet. Vesta is the largest asteroid and it has the total area of about 326 miles.
Meteors are more commonly known as ‘shooting stars’ or ‘falling stars’, but like we said they aren’t stars at all. The flash of light that is seen across the sky is called the meteor. When some debris enters the earth’s atmosphere and on doing so combusts almost immediately it results in the flash. The debris itself is the meteoroid. Meteoroids are formed when two asteroids clash and a small part breaks loose.
(Source: Wikipedia)
If a part of the debris called meteoroids survives the atmosphere and falls onto the earth’s surface it is called a Meteorite. The majority of the meteorites that have fallen on earth are very small in size, weighing only a few grams. Early in the 1900’s, a farmer found the largest meteorite ever found on earth in Namibia. It is the Hoba Meteorite and it weighs 66 tons! These meteorites are generally very rich in rare minerals and have a high market value.
Not all objects found in our solar system are cosmic in nature. There are hundreds of manmade objects that we have sent into the universe for research and exploration. The famed International Space Station is the largest artificial satellite in space and it is currently orbiting the earth.