Stephen Perry
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Space is as incomprehensible as it is awesome. Its true magnificence can be difficult to understand, even for an astrophysicist. Maybe that's why we often resort to simplified explanations and easy-to-understand pictures when discussing it. Maybe that's why basically everything we picture about space ranges from wildly incorrect to pants-on-head idiotic. To start with ...
When most of us think about the solar system, we think of this:
Can you guess what's wrong with it? That's right: everything. First: Earth is actually really tiny. Really, unbelievably, curl-into-a-ball-and-pee-a-lot tiny. Here's a sense of our mighty, life-carrying planet's place in our solar system's pecking order:
Lsmpascal via Wikipedia
It's OK to feel a little insecure.
Can you see Earth? Of course you can't. It's the pixel below the ever-so-slightly larger blue-green dot that is Neptune, which is below the slightly bigger dot that is Jupiter. To put that in numbers: There are approximately 11.21 Earths across the diameter of Jupiter. The sun is about 109.7 Earths across.
Now that we've established we're roughly the size of a hair follicle on the giant flaming testicle that warms us all, let's talk about planetary orbits. Most classic solar system charts present orbits as perfect circles, with the planets hanging out fairly close to each other at respectable, yet aesthetically pleasing distances. Reality, on the other hand, is a mess of slightly elliptical circuits, as per Kepler's First Law of Planetary Motion. Also, they're really far apart from each other:
NASA
Also, they're all at different angles, because nature can never make anything easy.
And let's not even discuss Sedna, the moody teenager of the solar system, only showing up for dinner before sulking away to its gloomy bedroom.
If you want to play with the abject terror that is the vastness of our own solar system, here's an interactive scale model. Or, hell, you can just watch these guys build one:
Note that they need the freaking Nevada desert to do so.
Quick: Which way is this comet going?
NASA
RIGHT TOWARD US.
If you said, "Toward the bottom right of the picture," you are wrong. In fact, if you said anything but, "I have no idea. I am a total dipwad. Please stop asking me things about space," you are also wrong.
We tend to assume the comet is basically a giant galactic hadouken, and its tail follows the main fireball-lookin' bit. But comets are essentially big hunks of ice and stuff, and every other thing we see about them -- the lights, the tail, everything -- is just the sun working its magic.
This is a comet:
NASA
Not pictured: the alien mothership following it to destroy us.
At around five astronomical units (one unit = 93 million miles, or Earth's average distance from the sun), the sun starts heating the comet with enough force to sublimate some of the ice straight from solid to gas, and the gas mixes with dust to form a halo around the comet called a coma. The tails (yeah, there are in fact two) grow from this. One of them is the plasma tail of ionized gases, and the other is just plain ol' dust.
The plasma tail forms when solar wind hits the coma and ionizes the gases, making it point directly away from the sun. The dust tail tends to curve toward the comet's orbital path, true, but it also gives in to the sun's radiation pressure (way worse than peer pressure) and steers away from the sun. You would too, if you were a celestial body. The sun is a bit pushy.
NASA
"I give you cancer. No reason; I'm just a dick."
Johan Pauly via Space Weather
From Rick And Morty to Futurama via The Magic School Bus, pop culture presents Pluto as an icy, bluish-gray hunk of crap, not unlike a space version of Antarctica. It's far away from us and the sun, so it must be cold, and cold things are blue, right?
Here's Pluto, courtesy of the New Horizons probe in July 2015:
NASA
"Well, look who came crawling back, Mr. 'You're Not Big Enough To Be A Real Planet'!"
Look, maybe we failed "colors" in kindergarten, but that's not gray or blue. That's definitely brownish-red. Pluto is basically the same color as Mars, but the reason for its color is much cooler: Pluto got its sick tan thanks to cosmic and sun rays screwing around with the methane on its surface and in its atmosphere. See, there goes the sun again, just roving around the solar system in its celestial Camaro, metaphorically shoving planets into puddles and ruining their Sunday best.
Pluto notwithstanding, which planet in our solar system has the shortest day? What about the longest? Common sense dictates that Mercury, as the smallest, has the shortest day, and Jupiter has the longest. Sadly, as is generally the case when we kick off an entry with a question, common sense can go and liberally suck it.
Alain r/Wiki Commons
Like black-hole-level suck it.
Jupiter, the largest planet in the game, has a day of just 9.9 Earth hours. If you lived there, you wouldn't even have enough time to marathon the Lord Of The Rings films between the sunrise and sunset. Meanwhile, the roughly Earth-sized Venus rocks a day that lasts a whopping 243 Earth days. And yet Venus' year is only 224.7 Earth days. If you lived on Venus you would have sweet, sweet sunshine for over a year, before being plunged into a year (and then some) of night. Yes, this is an excellent prompt for a Vampires Of Venus screenplay, and no, we're not sure why we're the first to have thought of it.
The rate at which a planet spins is determined during its creation, and it has nothing to do with its size or composition. As a star forms, it creates a spinning-formation disk, around which lumps of matter form planets.
European Southern Observatory
Or Galactus' eyes.
These proto-planets initially spin at the same speed as the disk, but as they interact with other material, their spinning speed increases or decreases until they settle on a safe orbit. From that point on, they spin the speed they did after their last interaction.
Science is slowly getting the hang of the intricacies of the planetary spin, and research indicates that the speed of a planet's rotation has a huge effect on its potential habitability. Presumably because you'd get super nauseated whipping around at Jupiter speeds. Please don't tell us that's not how it works. Our self-esteem just can't take any more hits.
The traditional definition of a moon is, well, the moon -- a much smaller celestial body orbiting a planet. But when scale, the bitter enemy of all who attempt to comprehend space, enters the game, we notice that a whole bunch of moons are not so much unassuming satellites as they are planets in their own right. Here's a look at our solar system's moons, with a couple of planets thrown in for good measure:
Primefac/Wiki Commons
Jupiter is the Duggar family of celestial bodies with 63 (confirmed) moons.
As you can see, Jupiter's Ganymede and Saturn's Titan may be moons, but they could easily steal Mercury's lunch money and give Mars a run for its money. Pluto, on the other hand, pays protection money to half the moons in the solar system, including our own.
Not that every moon even gets a planet to orbit. We know dozens of asteroids with small moons orbiting them. Here's Dactyl, one of the tiniest space things we've bothered to grant a name, and the asteroid it orbits, Ida:
NASA
So named because NASA still can't be sure it's not a potato.
Yes, that minuscule, one-mile dot out to the right is a moon, and it isn't even the smallest one. In January 2015, NASA noticed a tiny, 230-foot moon orbiting the 1,100-foot asteroid BL86. Here's the cutest buddy movie starring two tiny rocks in the unforgiving emptiness of space you'll see all week:
"IT'S A PERFECTLY NORMAL SIZE, THANK YOU VERY MUCH."
Where is the edge of the solar system? It's Pluto, right? Real planet or not, at the average distance of 39.5 astronomical units, it's the farthest thing we have from the sun, and therefore its orbit surely marks the walls of our cosmic crib.
Nope. Not even close.
To find out where the edge of the solar system is, we first need to ask another, seemingly stoned question: What is the sun?
"It's a star, stupid," you say. Fair enough. But what is a star?
Right about now is the point where you roll your eyes and stop talking to us while we giggle at our own hands. But no, that's a serious question: A star is essentially a compact series of gas explosions so hot that its vast supply of hydrogen is constantly undergoing nuclear reaction, all across the star. Like so:
It's like farting, only with a hydrogen bomb.
The thing about a giant ball of nuclear explosions is that its influence extends well beyond the flaming disc that we see in the sky. The sun's solar wind constantly blows in all directions, spewing plasma and particles into space at supersonic speeds. All that sound and fury does serve a purpose. It keeps the interstellar medium -- the dust and gases from the space between the stars -- at bay, away from our pristine little solar system. The solar wind pushes the interstellar medium away, creating a massive shockwave known as bow shock. The solar wind eventually weakens, slowing enough to hit subsonic speeds, and this boundary is called the termination shock.
NASA
If you look close enough, at the center of the sphere, you can see a tiny naked Arnold.
That's the blue bubble in the above picture, estimated to be up to 94 astronomic units away (based on Voyager 1's measurements). And it's not the end of the sun's effective range -- merely the beginning of the next phase, called the heliosheath. Here, the solar wind is advancing at more leisurely speeds, a subsonic, compressed, and turbulent thing still capable of pushing the interstellar matter in front of it. Finally, we reach the heliopause, where the solar wind and interstellar matter finally cancel each other out, sit down, and start playing canasta. This marks the outer rim of the sun's heliosphere, and thus our solar system. We are now at least 121 astronomical units away from the sun -- three times farther away than Pluto.
NASA
"Everything the light touches."
The reason the heliosphere is oval, as well as why the bow shock is a giant wall on the thin side of the heliosheath instead of an all-encompassing tidal wave equidistant around us, is simple: Our solar system is constantly moving. We're essentially a missile that screams through space at 45,000 miles per hour, the sun's constant solar wind bombardment pushing aside interstellar bullshit as we go.
Yep, our whole solar system is basically a giant rampaging muscle car gleefully tearing ass through space, and our sun is a cowcatcher bolted onto the front of that car, flinging everything out of our path with extreme prejudice. And they say astronomy is boring.
"Well, gentlemen, after viewing your new promo, the president has decided
to increase NASA's funding by 8,000 percent."
You should totally follow Stephen Perry on the Twitter. He is very apprentice at doing the tweeting.
It turns out that we have wildly awful perceptions about a lot of things. Like, you know, that velociraptors resembled birds more than lizards or that vikings were pretty good cosmetologists. See that and more in 6 Things From History Everyone Pictures Incorrectly and 5 Scenes From History That Everyone Pictures Incorrectly.
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