Date: February 8, 2011
Title: The “Other Stuff” in the Solar System
Podcaster: Rob Berthiaume
Links: www.yorkobservatory.com & www.youdontfreezeinspace.com
Description: The planets get all the attention when people think about what’s in our solar system. This podcast gives an overview of all the “other stuff” that’s hanging around our Sun.
Bio: Robert Berthiaume is working towards an MSc in atomic physics at York University in Toronto, Canada. When he can get away from building diode lasers, he rides his motorcycle when the sun is up, and shares the stars with the public at the observatory when it’s not.
Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by a small furry creature from Alpha Centauri. And we’ll be saying a big hello to all intelligent life forms everywhere. And to everyone else out there, the secret is to bang the rocks together, guys.
Transcript:
Hi there. I’m Robert Berthiaume bringing you the February 8th edition of the 365 Days of Astronomy podcast from the York University Observatory in Toronto Canada. Our little corner of space, our solar system, is made up of an average sized star we call the Sun, and around it are 8 balls of rock and gas, orbiting around it, going in circles over and over again, like cars around a racetrack. At least that’s the picture that is presented on most stickers, books, mobiles, placemats, puzzles, and posters. But there’s way more to it that isn’t mentioned in this one star, eight planet description. Just like when the White House is simply described as the place where the US president lives. It’s not just your regular house with Barack and Michelle playing Jenga with the kids in the den. There are literally hundreds of people buzzing around the place doing different jobs, but we never hear about them, they don’t get noticed. And when it comes to our solar system, we rarely hear about the trillions of other objects that are buzzing around the Sun between the planets. So today I’d like to swing the spotlight away from Mars and Saturn and the rest who are always in it, and shine some light on the smaller, less famous, less thought about “other stuff” in the Solar System.
The largest non-planet citizens in the Solar System are known as dwarf planets. These are objects that orbit the sun, and are large enough to be ball shaped (scientists would say they’re in hydrostatic equilibrium), but too small to be able to sweep up or fling out other large-ish objects in their section of their orbit. They’re a few thousandish kilometres across and have thin atmospheres There are 5 such dwarf planets as this podcast is recorded, with more likely to be discovered. Pluto had the pleasure of being called a planet for 75 years, between its discovery in 1930 to 2006, when the formal definition for what a planet is was decided. Eris, discovered in 2003, kicked off the debate as to what should and should not be called a planet. Astronomers originally thought it was larger than Pluto and was informally called the 10th planet for a while, but this was put to an end, again, when the planet definition was solidified. Both these dwarf planets share their orbital zones with a group of things known as Kuiper Belt Objects, which include two more dwarf planets, Haumea and Makemake. The 5th dwarf planet is much closer to the Sun, and much closer to us. Ceres, the first asteroid ever discovered, hangs out in the main asteroid belt, a region of space between the orbits of Mars and Jupiter. It too was thought of as a planet for a few decades in the 1800s, but more discovered and observations of other asteroids made it clear that these asteroids were fundamentally different from the other planets.
And just what are asteroids? These objects are found all around the solar system, and are made of chunks and globs of rocks and metals that are about car-sized and larger, up to several hundred kilometres across, when they would be large enough that they’d have strong enough gravity to pull themselves into a ball shape. Some orbit the Sun in the Main Asteroid Belt, but there are plenty of others that orbit closer to the sun and further away from the sun. Some of the closer ones, called NEOs for Near Earth Objects, actually end up crossing Earth’s orbits sometimes, and if this happens with just the right timing, the asteroid hits Earth and kills dinosaurs. A particular class of asteroids, known as Trojans, get locked into orbits ahead or behind a planet, and lead or follow the planet as it goes around the Sun at exactly the same rate, with zero chance they’ll hit anything but themselves. A lot of asteroids used to be parts of larger things early in the solar system’s life, but these things smashed into each other and ended up in smaller pieces. Some asteroids are solid, others are loosely held together piles of rubble. Some asteroids actually have other little asteroids orbiting them, like they’re trying to be a planet with a moon. So there is tons of variety in how asteroids are made and how they behave, but one common feature is that there isn’t a whole lot of gas or volatile material that vaporizes at lower temperatures present.
In the case where a similar sized object does have gases or water or methane or some other volatile present, we call this thing a comet. Think of them like big dirty snowballs or icy dirtballs. The snowy stuff starts melting and vaporizing if the comet ever gets close to the Sun, and it produces a cloud of gas and dust, and sometimes big flashy tails behind it. But most of the time, a comet is just too far away from the Sun where it is cold enough to keep all this stuff frozen. There are millions and billions of comets that live out in the outer reaches of the Solar System, in a place called the Oort Cloud. Every so often, something will cause some of these to fall inward towards the Sun, where they heat up and start looking pretty. If they go around the Sun enough, and enough stuff boils off the surface, they end up being just rock. Astronomers observe some asteroids that they think may have been comets in the past.
If you’re not big enough to be a comet, you’re known as a meteoroid. Anything that’s floating around up between the planets which is the size of a grain of sand, or a pebble, or a rock, you’re pretty much at the mercy of the other big things. You’ll orbit around and most likely at some point get close enough to an asteroid or planet or dwarf planet that you’ll be flung into a new orbit, or you’ll collide, and become a part of the now bigger object. Several thousand kilograms of this stuff falls into Earth’s atmosphere every day, and when it does, it heats up and creates a streak of light in the sky; a shooting star. Lots of this stuff is cleaned up by bigger planet, but new meteorites are always being made when similar sized objects collide or when comets swing by the Sun and vent off stuff from their surfaces.
The smallest stuff floating around in space has the same name as the smallest stuff floating around your home: dust. These can be individual molecules or ice and rock, tiny, silt-sized particles, and everything in between. This stuff is neat, because you can actually see it in space. Asteroids and comets for the most part require a telescope to observe, and meteoroids are too small to see even with the largest telescopes, but if you have a dark sky, you can see the collective light reflecting off of all these little particles as something called the Zodiacal light or the Gegenschein.
I’ve spent the past few minutes giving you some info about the “other stuff” that is found in our Solar System. And its my hope that I failed to provide enough details and left you unsatisfied with the amount of content I provided. But hopefully I’ve created a little spark that may get you to go to the library or go online to do a little research of your own on cosmic dust, or comets, or solar wind, etc. Thanks for listening, I hope you learned something and had a little fun. Until next time, this is Robert Berthiaume wishing you clear skies and good times.
End of podcast:
365 Days of Astronomy
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