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Q: Is there anything unique about our solar system?

Physicist: Maybe.

As far as stars go, ours is a dull as dishwater, middle of the road, dime a dozen, main sequence star. You can’t spit in space without hitting a Sun-like star. So this question is really about the stuff around our Sun. But, beyond their stars, comparing solar systems is a little tricky.

A solar system is basically a star (sometimes a couple of them) with a tiny bit of grit left over. Not only does our Sun comprise 99.86% of the mass of our solar system, but it’s disproportionately “loud”. While the Earth may have a smattering of radio antennae pumping signals into space, the Sun is a screaming ball of electromagnetic noise almost a million miles across. And not for nothing: it’s seriously bright. So finding stuff around other stars is difficult, not just because everything other than stars is tiny, but because of the stars themselves. In fact, most of the techniques we have for detecting stuff around other stars involves looking at the effect of said stuff on their host stars. Ultimately, if you really want to get a good look at other solar systems you’ve got to get off of your podunk planet and go there.

That said, we are now living in the century of planetary discovery. Every civilization has known about 6 planets: Mercury, Venus, Earth, Mars, Jupiter, and Saturn. Uranus, Neptune, and Ceres were discovered in the 19th century. Pluto and the first few exoplanets were discovered in the 20th century. But in the first decade and a half of this century we’ve discovered dozens of new dwarf planets in our solar system and thousands of exoplanets in other solar systems. The rate of discovery is ramping up exponentially.

The methods we use to detect planets around other stars are much better at detecting planets that are big (which isn’t surprising) and close to their stars. So the easiest planets to find are “hot Jupiters“. But based on what we’ve seen so far it looks like damn near every star in the sky, even binary and trinary stars, have planets in orbit around them. Despite the difficulties in finding any planets, we’ve confirmed hundreds of solar systems with multiple planets (which strongly implies that practically all of them have multiple planets). And that’s based on methods that look at only a tiny fraction of the sky and miss the majority of planets.

Even better! By far the most common element in the universe is hydrogen with oxygen a distant third. So we can expect to find H 2 O (water) all over the universe, including on exoplanets, and when we look that’s exactly what we find. That doesn’t necessarily mean that there’s life out there, but if it’s around it’ll definitely have lots of places to do its living.

So here’s the point. It’s really hard to see planets around other stars, we miss most of them, and we’ve only looked at a tiny fraction of the nearby stars. And yet! We’re finding planets freaking everywhere. Big, small, hot, cold, rocky, gaseous, short years, long years, dry, or wet. The shocking variety and preponderance of planets has completely rewritten our ideas about planetary and solar system formation. We once thought that solar systems would all more or less “follow the same script” during their formation and end up as variations on our own. Instead we find that each is surprising and unique. Our solar system is unique like a snowflake in a blizzard is unique.

The top two pictures are from the (free as of writing) exoplanet app and that picture of Earth is from space.

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