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What's the Deal With Pluto?
When Will the Universe End?
We all have our ways of remembering the order of the planets. "My Very Educated Mother Just Served Us Nine Pizzas," is a common pneumonic that pre-dates Pluto's demotion to a dwarf planet. In 2007, Astronomy magazine suggested the pluto-less: "My Violent Evil Monster Just Scared Us Nuts". Regardless of how you learn to remember their order, it's very unlikely that our solar system will be getting any new planets or swapping positions any time soon. How did we end up with four rocky planets in the front closest to the sun and the four gas giants farther out? Questions like this will always be an ongoing debate until we can see a planet formation with our own eyes (don't hold your breath). Planetary scientists watch other developing stars and planetary systems and apply what they learn to our solar system. Astronomers know that solar systems begin as clouds of gas and dust spinning through space. If there's enough mass in the center, most of the mass will collapse into a star, while the surrounding matter coalesces into planets, moons, asteroids, comets, and everything else out there.
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But just mushing together gas and dust isn't detailed enough to describe this process on it's own. A study published in 2015 in the journal Nature wanted to see what would happen if they tried to recreate the early conditions of an solar system in their lab. They added tiny pebbles into a spinning mix of gas and dust. Pebble Theory says planets form when tiny rocks revolving around an early sun have enough gravity to pull other pebbles, gas, and dust into them, making them bigger. Slowly the bigger rocks attract smaller ones, gaining mass and gravity, and forming their own accretion discs of matter. Eventually, these will become proto-planets, planetesimals and (if they build up enough mass) planets. All the planets in our system developed rocky cores. but some had more mass and gravity than others and were able to hold onto their heavy, gaseous atmospheres. The small mass of the inner solar system planets just didn't have enough gravity to keep the big atmospheres we see on the gas giants. Astronomers theorize that the early inner solar system was maybe 40-times hotter than the outer regions, which also played a factor.
Amy's favorite planet is Venus because it rotates backwards, is incredibly hot, but is about the same size as the Earth. To her, it's like an inside-out and backwards version of the Earth. What is your favorite planet? Tell us in the comments, and we promise we won't judge if you are still #TeamPluto.
Jupiter bumped giant planet from our solar system (ScienceDaily)
"It's like something out of an interplanetary chess game. Astrophysicists have found that a close encounter with Jupiter about four billion years ago may have resulted in another planet's ejection from the Solar System altogether."
Planets and How They Formed (Lcogt.net)
"The planets in our Solar System are believed to have formed from the same spinning disc of dust that formed the Sun. This disc, called the solar nebula, was composed mainly of hydrogen and helium, but also had other elements in smaller proportions."