Our Solar System is more crowded than you may realize
Growing up I had a game called “Operation”. Kids would use a metal rod to try and perform an operation on a patient, each of the major body parts was a different shape and color. Later in life I had the good fortune to be able to scrub in to an actual operation — turns out your insides are actually very different, more dense and far more complex than portrayed in the game. It was an eye opening experience although I would not recommend it before, or after, lunch. The simplicity of the Operation game reminds me our Solar System in terms of the typical portrayal we are shown. Most pictures of our Solar System show the planets all lined up, roughly equal in their distance apart from one another, on very similar planes and orbits around the Sun. The pictures show nothing in between or around each planet other than the incredible rings on the giant gas planets of Jupiter, Saturn, Uranus and Neptune (although sadly often even the rings aren’t shown). In scale, the actual distances are much different than in the image above. Mercury, Venus, Earth and Mars are fairly close compared to Neptune which orbits at a much, much greater distance. The image below, although still showing everything lined up and on the same plane in a way they would never be, at least shows a much more accurate representation of the distances (it’s done to scale) between the major planets in our Solar System:
But even here, between the planets all you see is empty, black space. Is it really that empty? Not at all. Within our own solar system it turns out there are literally multiple millions of various sized objects in motion. It’s estimated orbiting the Earth alone there are some 500,000 bits and pieces of rock between 1 and 10 cm in size. All this material stems back to the creation of our solar system, some 4.6 billion years ago. Scientists believe a nearby exploding star cause a cloud of stellar dust to collapse and our star formed as a result of the great pressures involved (along with lots of extra material which coalesced into planets, moons, meteors and lots of left over objects and dust). Hundreds of thousands of those rocks orbit an area between Mars and Jupiter, we call that the asteroid belt. The meteors (which include even a dwarf planet 950km in diameter) in the asteroid belt are mostly irregular shaped bodies ranging from large objects down to granules of dust. Unlike typical movies which often picture this area as crowded (and ships having to zig and zag their way through it), in reality the asteroids in the belt are very spread out — the distance between objects in the asteroid belt averages over 600,000 miles (nearly 25 times the circumference of the Earth). Because it’s so spread out, spacecraft have been able to pass easily through the asteroid belt without concern of collision. It’s worth noting, gravitational forces can result in asteroids being thrown out of the belt towards the inner solar system — it’s these types of objects that can pose a threat to Earth (and likely one of these that wiped out the dinosaurs). But I digress …
Much further out from the Sun is the vastly larger Kuiper belt, extended from the orbit of Neptune to the furthest orbit of Pluto and beyond. This belt is composed of numerous types of objects also mostly left over from the formation of our Solar System, including hundreds of millions of small icy bodies and at least three dwarf planets. Observations of this belt have resulted in an estimate of more than one trillion comet nuclei existing in the Kuiper belt. One object in this belt we are all familiar with is Pluto, it’s the largest object in the Kuiper belt and was reclassified as a dwarf planet in 2006 when it was downgraded from full planet status (creating the “Size Doesn’t Matter — Save Pluto” movement).
A thousand times more distant from the Kuiper belt, located at the outskirts of our Solar System in the Interstellar Medium (the space between star systems, in this case between our system and Alpha Centauri) is the theoretical Oort Cloud. Voyager 1 will reach that area in about 300 years and take about 30,000 years to pass through the Oort Cloud. Not much is known about the Ooort Cloud although there are some excellent Oort cloud jokes floating around (pun intended). Jokes aside, the Oort Cloud is believed to be composed of billions or even trillions of icy objects. Scientists estimate that many of those objects are larger than entire mountain ranges found on Earth.
The impetus to write this article stemmed from a Google search last week, I searched with the text “how many objects are in our solar system” and the top result (which should have included asteroids, comets and meteroids, etc.) was “8 planets, 5 dwarf planets, 181 moons and 566,000 asteroids”. That answer was close, off by only a few hundred billion or so.
