Are you ready? Cause I’m totally about to drop some dope-a$$ science.
Having a bad day? Feeling insignificant? Well, I’m about to make you feel a whole lot worse. I do that sometimes.
Let’s put your place in the universe into perspective here. The distance between the earth and the sun is roughly 150 million kilometres. Astronomers call this an astronomical unit or AU. So Earth is 1 AU from the sun. Jupiter is roughly 5 AU from the sun at aphelion (its furthest distance). Saturn’s furthest distance from the sun is just over 10 AU. That’s 1.5 BILLION kilometres.
Further out, you have the so-called ‘ice-giants’. Uranus (hold your sniggers) has an average distance of 19.2 AU but at aphelion is over 20 AU from the sun. That’s double the distance between Saturn and the sun. Next is the planet Neptune. Neptune’s average distance from the sun is 30.1 AU. While mostly featureless and kind of bland, Neptune is nonetheless pretty…let’s call it the Taylor Swift of planets. Yes I went there:
Beyond Neptune, you have the dwarf planet, Pluto. Pluto is located in an area we call the Kuiper Belt.Whether Pluto can accurately be described as a planet in the conventional sense is still a contentious issue among astronomers.
Numerous other dwarf planets have been found in the Kuiper Belt and are referred to as Kuiper Belt Objects (KBOs).
The orbital distance of Pluto varies hugely. At its closest point, it is actually closer to the sun than Neptune at a distance of 29 AU but at its furthest distance, it is a whopping 49 AU from the sun. Woah, Pluto. You cray-zay.
Of course, the solar system doesn’t just contain the eight planets (and Pluto). Nope. The solar system extends as far as the sun’s gravity has an effect on an object. Some scientists claim that the outer reaches of the Kuiper Belt mark the edge of our solar system. However, it has been hypothesised that there exists a massive cloud of comets which surrounds our solar system in a spherical shape known as the Oort Cloud. It has been theorised that the Oort Cloud could stretch from between 2-5,000 AU from the sun to…wait for it… ONE HUNDRED THOUSAND AU. That’s over a LIGHTYEAR. (Which I’ll get to…)
We’re not even entirely sure that the Oort Cloud exists but it has been given as the likely location of the possible dwarf planet, Sedna. Sedna is a planetoid which takes…wait for it again… 11,400 YEARS TO ORBIT THE SUN…or you know, the average length of an Al Gore speech. It has a wildly eccentric orbit. At its closest point, it is roughly 76 AU from the sun. At its most distant point….IT IS 937 AU FROM THE SUN. Go home Sedna, you’re drunk.
Most astronomers would say that the solar system effectively ends where the sun’s wind (solar wind) meets the interstellar (the space between stars) wind. This is at a distance of roughly 120 AU and is the current location of the two Voyager space probes launched in the 1970s.
So, that’s the solar system. But our sun, Sol, is not even a big star in the grand scheme of things. It is only one of an estimated TWO HUNDRED BILLION in the Milky Way Galaxy. Here are some pictures from my 3D SkyORB app to put all of this into perspective:
When we are taking about objects as large as galaxies, astronomical units do not work anymore. We need a new unit of distance to measure such huge distances. A lightyear is used to measure distance and not time, as some people erroneously assume. A lightyear (ly) is made up of over 63,000 astronomical units. In kilometres that is TEN TRILLION KILOMETRES.
Within our galaxy, it is estimated that there are roughly 200 billion stars but there could be many, many more. The thing is, there is A LOT of space between stars. Our nearest star is Proxima Centauri, located 4.24 lightyears away. It’s not visible from Earth, and even if it was, it wouldn’t be visible in the Northern Hemisphere. Does 4 lightyears sound close? In cosmic terms, it’s practically our back garden. However, it would take the New Horizons spacecraft a total of 78,000 years to get there, and that’s travelling at a speed of 60,000 km/h. You’d better pack a lunch.
So what exactly is a lightyear? Well, it’s the distance light travels in a year. Think about this: when you look at a star in the night sky, the light that you are seeing left that star long ago (depending on its distance) and you are essentially looking into the past. For example, the star Deneb in the constellation Cygnus is located an estimated 2,600 lightyears from Earth. So when you look at Deneb, you are viewing it as it was over two and a half thousand years ago.
Feelin’ small yet? Grasping just how huge a lightyear is? Well, the Milky Way is roughly 100,000 lightyears across. Pretty big, right? The Milky Way is part of a cluster of galaxies called the Local Group. There are more than 54 galaxies in the Local Group and we’re not even the biggest one. The Andromeda Galaxy is, and it’s located around 2.5 million lightyears from Earth. It is so big that it is actually visible with the naked eye from Earth. It is one of my favourite Messier objects to observe with my binoculars and I just love knowing that I’m observing light from something which has been travelling towards me for two and a half million years. Woah, man. It’s thought that there may be over a trillion stars in the Andromeda Galaxy…and we’ve only properly observed a fraction of the stars in our own galaxy.
So there you go guys. You’re basically on a small rock, orbiting a small star, in a small arm of a spiral galaxy that isn’t even the biggest one in its group. And even that group of galaxies is in a bigger group: The Virgo Supercluster. And there are billions of galaxies in the known universe. I hope your head doesn’t hurt too much.
P.S. Although I am pretty awesome 99% of the time, there are very rare instances that I am wrong. If I have been mistaken about anything here, please let me know and I’ll fix it…while secretly hating you.