“You just won’t believe how vastly hugely mindbogglingly big it is.” – The Hitchhikers Guide to the Galaxy, Douglas Adams

Welcome to the first post of Spacelabh! This time we shall be briefly explaining some of the big words that you find in the world of astronomy and astrophysics to give you all a base from which we shall work up from!

Lets dive in!

In this section, I shall be explaining what some of the words you are most likely to see when exploring the wide expanse of space. I won’t go into too much detail here, as these topics will be discussed in more detail in later blog posts. This is just to give you a rough base for you to start building on. Not every word will be here, and I am sure you will have more that I will miss out. Feel free to add these words into the comments and I can explain them for you!

Firstly I am going to explain the difference between astronomy, astrophysics and astrology. These are often lumped together as the same thing, but they are all very different to each other. Astronomy is the study of space and where things are in space. The easiest way to understand it is that astronomy is stargazing. Seeing where each star is in relation to each other, and where all the different planets and galaxies exist is astronomy. Astrophysics is what I do. I look at the physics behind the stars and planets, seeing how they became, how they will evolve and how they interact with each other. Astronomy and astrophysics often go hand-in-hand with each other, which is where the confusion begins. Astrology is totally different. Astrology is about looking at the constellations and planets and using their positions to predict the future and various happenings in day to day life. Astrology is not the same as astronomy or astrophysics. The constellations are used in astronomy to find the way around the sky and as reference points, but not much else.

The biggest word in the sense of area is universe. The universe is everything. Absolutely everything. This includes all the galaxies, stars, planets, black holes, you, me, your family, everything! Space is often used to describe everything, but universe is the more ornate term.

Going down in scale, the next group of objects is a galaxy. This is a collection of stars and planets, with maybe a black hole in the middle keeping it all together. Our galaxy is the Milky Way (not the chocolate bar). This galaxy includes our solar system, all the stars you can see in the sky at night and then many more stars too. Our closest galaxy neighbour is the Andromeda galaxy. This is very distant from us, but on a very clear night, you may be able to see it as a smudge in the sky. A collection of galaxies is called a Local Group. This usually consists of many large and small galaxies in a similar area to each other.

Keeping going down in scale, we end up at the solar system. This is a collection of one star and its associated planets that orbit it. Our Solar System includes the Sun, 8 planets, two rock belts, many dwarf planets, many moons and lots of satellites. A simple way of picturing all these areas and how they all fit tougher is by picturing the Earth as your house, the Solar System as the street you live on, the galaxy as the town or city you live in, the Local Group as the continent and the Universe as the whole world. Check out this awesome graphic. This is a to scale representation of our Solar System if the Moon was only one pixel wide. I would suggest taking a look at some of it. You’ll need a lot of time if you look at all of it!

A star is a circular luminous body that emits light and other radiation by burning gas held together under it’s own gravity. Stars come in many sizes. Our Sun is a relatively low mass star compared to those in the universe. It is also fairly dim comparatively too. When measuring the mass and luminosity (how bring an object is) of stars, they are often described in terms of our Sun. This makes it easier to understand how bright or large the star is as we know how bright and big our Sun is. Stars are very far away which means all the stars we see in the sky may not be there anymore. When looking into the night sky, you are technically looking into the past. It has taken the light possibly millions of years to reach us. The light that we see may be what the star looked like when the dinosaurs were around, but only know are we seeing that light on Earth!

A planet is described as having an elliptical orbit around a parent star and has enough gravity to hold itself together. In our Solar System we have 8 planets. These are, in order from the Sun, Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune. These planets all orbit in the same plane around the Sun, meaning that they all go around the Sun approximately in the same line of sight as the Sun. The planets also have enough gravity to hold themselves together in a spherical shape. These are what defines planets in our Solar System, and is what declassifies Pluto. Pluto orbits the Sun at a different angle to the rest of the planets, has a highly elliptical orbit which means sometimes it is closer to the Sun than Neptune is, and is also not spherical enough to be classed as a planet. It has been classified as a dwarf planet though. These are smaller objects that are similar to planets in our Solar System, but don’t quite meet the expectations. There are currently 5 officially recognised dwarf planets in our Solar System, called Ceres, Pluto, Haumea, Makemake and Eris.

That’s it for this time! If there are any other words that you want to know the meanings of, don’t be afraid to post them in the comments and I shall get back to you with what they mean! Thanks guys!