The size of our solar system
I’m reading Pale Blue Dot by Carl Sagan at the moment. I’d heard of the Kuiper Belt and the Oort Cloud before but thought they were small clusters of rocks somewhere in between the planets.
No so.
The Kuiper Belt is a collection of big rocks ranging from a kilometer in size up to Pluto (yep, Pluto is now part of that collection) which is 2320km across and others that are even larger. It’s in a disc shape starting at Neptune and extending for about 3 billion kms (20AUs) and Neptune, which is the furthest out of our planets, every once in a while manages to pull one of these objects out of its orbit around the sun and occasionally flings it inwards causing much of the pock-marking we see on the moon and other planets. Including Earth. Neptune is throwing rocks at us.
The Oort Cloud extends beyond the Kuiper Belt, is in the shape of a sphere rather than a disc, extends a long way out (the Kuiper Belt extends to 50AUs and the Oort Cloud as far as 100,000AUs). All of these objects are held in orbit by the force of the Sun’s gravity.
To get an idea of the size of our solar system take a look at the ongoing travels of Voyager 2. It was launched in 1977, sling-shotted around Juipter in 1979, did the same to Saturn, Uranus and Neptune in 1981, 1986 and 1989 respectively and continued on outwards travelling at a speed of 3.3AUs per year (55,000km/h).
Travelling at 55,000km/h it’ll take something like 20,000 years to clear our solar system. If it were heading toward the nearest star to us it would take about 80,000 years to get there.
Let’s face it, unless we invent a snappier way to travel we’re going to have a long term plan for this planet we live on.
