We are part of a system. Our planet is in the Solar System which is in a galaxy accompanied by other billions of stars in it. There are trillions of other galaxies in the universe. The closest of them is about 2.2 million light years away. A light year is the amount of distance travelled by the light in a year whereas the speed of light is two hundred and ninety nine million, seven hundred and ninety two thousand, four hundred and fifty eight (299,792,458) metres per sec.
Galaxies have been studied by the astronomers are of different types and shapes. The four most common types of galaxies are:
- Elliptical Galaxies: These type of galaxies range from nearly spherical to almost cigar – shaped, and have enormous differences in the number of stars and their sizes; giant elliptical galaxies may contain only a few million stars and have a diameter of a few thousand light years; giant elliptical can contain thousands of billions of stars and be far larger than our own galaxy.
- Normal Spiral Galaxies: Although the structure of spirals makes them look as if the arms are the result of some process of “winding up” as the galaxy rotates, this is not the case. The arms have existed for billions of years, and stars nearer the nucleus orbit the galaxy faster than those on the edges, so the arms cannot be lasting structures but no more akin to ripples in a rotating whirlpool. Spirals are normally classified by the opening and structures of their arms.
- Barred Spiral Galaxy: These are similar in structure to the normal spiral galaxies, but have a bar on either side of the nucleus, in which the spiral arms originate. Roughly one third of all spirals are barred, and these are classified in a similar way to the normal spiral galaxy.
- Irregular Galaxies: As suggested by the name, these are the galaxies that have no particular identifiable shape or structure. They tend to be the small satellites of other larger galaxies, such as the Magellanic Clouds that orbit the Milky Way. It is thought that their irregular shape is caused by the gravitational disruption of their larger companions.
According to astronomers if we are at a point ten million years from the Earth, we might just be able to see the two major galaxies of our local group – the Milky Way and the great Andromeda spiral, the other smaller members would be all but invisible, ghostly specks giving no indication of the billions of stars they contain. Ten times further away, at a distance of one hundred million light years away from the Earth, we can see that there is still a structure to the universe. There are many clusters of galaxies, similar to our own local group which is the galaxies that are closest to the Milky Way – some of these clusters are tens of millions of light years across. But even that far in the universe we are not at the limit of order. The clusters of the galaxies join together to become super clusters, hundreds of millions of light years in diameter.
Lately astronomers are trying to find out the shape of the universe whether it is round or flat. Supposing that the universe is round will mean that if we travel into the space from earth now we will sometime in future come back from where we started and that means back to the earth, it is just like if we travel on earth in a straight line we will get back to the point where we started. On the other hand if the universe is flat we will just go into the infinity.
An astronomer who has been working on this project was trying to find out the mass of the known universe to the astronomers that he could work out the total amount of the gravitational force they create on the universe and than work out the total amount of the gravitational force required to maintain the universe in a certain shape. When he worked out the total mass and the total amount of force acting on it, he found out that this gravitational force was just 5% of the total amount of the gravitational force required by the universe to even keep it in a flat shape and to keep the universe in a round or curved shape it requires a bigger force than that to keep it in a flat shape. Therefore, what the astronomers gathered from that was the universe contains a very strong unknown force which makes up the rest of the 95% of the force required by the universe to keep it in a shape. As astronomers cannot see it yet and do not know what it is so they have named it “Black Energy”.
It has not been easy for the astronomers to make all these discoveries. They had to make plenty of gadgets to find these things. One of those is the VLT which stands for ‘Very Large Telescope’. It is named that because it is the biggest telescope on the earth at the present time. There is also another machine called VRS standing for ‘Very Small Rays’. It catches the microwave rays coming from the distant stars from all parts of the universe. It has helped the astronomers to discover new galaxies and stars in the farthest corners of the universe. With the help of VLT and VSR, in a way the astronomers are looking back in time because the light has been travelling from those stars from billions of years ago and we are getting an image of those stars or galaxies as they were billions of years ago. So far astronomers have been able to take pictures of stars in their stage after just fifteen million light years of the Big Bang. This will help astronomers to look at the universe when it was very young and it will help them to make other discoveries in this field.
Here's what a star student thought of this essay
Quality of writing
The candidate demonstrates a good understanding of the physics topics discussed and they have used appropriate scientific terms. However there are a few spelling errors which probably could have been avoided had the candidate taken the time to proof read their work. That said there are no real issues with grammar or punctuation.
Level of analysis
The candidate has taken the time to undergo independent research, this is apparent as they discuss several topics that you wouldn’t come across in A-level physics. There is a practically interesting paragraph about the mythology of astronomy and how the stars and constellations where worshipped. As well as being interesting to read this shows the candidates interest in their work and that they are capable of working independently. However the candidate has failed to write a conclusion. It is necessary to conclude your work as this allows you to summarise key points and ideas and gives a personal response to the topic, this is your chance to leave the reader with a good impression.
Response to question
The candidates introduction is reasonably good, they have tried to engage the reader by mentioning mankind's constant desire to explore space. However an introduction should also include a brief description to introduce your set topic and you need to clearly state exactly what you plan to discuss. Furthermore the candidates response seems jumbled, they have amalgamated several different facts but the essay itself doesn’t really flow and is hard to follow in places. This could have been avoided if the candidate had taken the time to set out a plan and think clearly about what they wanted to discuss.