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  • [♪ INTRO]

  • Right now, we know of eight planets in our solar system, but for more than a century,

  • scientists have been searching for number nine.

  • It's a proposed super-Earth: a planet past Neptune much larger than our own.

  • Over the years, there's been some evidence that it might exist, and this week,

  • researchers published even more.

  • On Tuesday, scientists announced the discovery of a new, extremely distant object beyond Neptune.

  • It's detailed in a paper submitted to the Astronomical Journal, and it's named 2015 TG387.

  • And while it's not a planet itself, it could point us to the long theorized Planet 9.

  • The object is pretty tiny, with a diameter of only about 300 kilometers,

  • almost 90% smaller than Pluto's.

  • And it's pretty far out. No, like, literally way, way out in the solar system.

  • When it was first observed in 2015, as part of an ongoing survey,

  • it was about 80 astronomical units, or AU, from the Sun.

  • That's 80 times farther from our star than the Earth,

  • or more than twice as far as Pluto is right now.

  • But comparatively speaking, that's actually really close to us.

  • For 99% of its 40,000-year orbit, this object is so far away we can't even see it.

  • After years of observation, researchers have calculated that, at its farthest,

  • it's a whopping 2300 AU from the Sun, much farther than any other known object.

  • So far, we've only found two other objects with orbits comparable to this:

  • the dwarf planet Sedna, and the planetoid called 2012 VP113.

  • These objects are so far out that their orbits are mostly unaffected

  • by the gravity of the eight known planets.

  • So by studying them, we can learn about the outer solar system and map what's going on out there.

  • And these orbits may already be pointing to something big.

  • All three of these objects, including TG387, share similar orbital paths,

  • almost like they're being shepherded by something larger.

  • According to the researchers, that object could be the elusive Planet 9.

  • To learn more, the researchers ran simulations to see how the gravity of a

  • hypothetical Planet 9 would affect the orbits of these objects.

  • And the results were promising.

  • For one, they showed that these objects did maintain stable orbits.

  • In other words, their current paths wouldn't be messed up if a Planet 9 existed out there.

  • The results also confirmed that a hypothetical planet could be shepherding the small objects.

  • That could explain why Sedna and TG387 take similar paths.

  • But to be sure we need more data, or a direct observation of the planet itself.

  • Scientists are looking, but since estimates suggest Planet 9 would never get

  • closer to the Sun than 200 AU, it's going to be pretty faint and tough to see, if it exists at all.

  • Now, even if another planet does exist, don't expect us to send astronauts there any time soon.

  • Even if we could send a crewed mission that far, research published on Monday suggests

  • we might have trouble surviving the journey.

  • According to the study, which was published in the Proceedings of the National Academy of Sciences,

  • long-term space travel has the potential to seriously damage our GI tracts.

  • The GI, or gastrointestinal tract, is the organ system we use to digest food.

  • And this new paper suggests that space travel could make it

  • less effective at absorbing nutrients and could potentially cause tumors.

  • It's all thanks to our good friend cosmic radiation.

  • Cosmic radiation mostly comes from objects beyond the solar system, and there are a few

  • types of it, including the extra dangerous heavy-ion radiation.

  • It comes from supernova explosions,

  • and is made of certain atomic nuclei accelerated to near light-speed.

  • Because of its mass, it's much more damaging than gamma and X-rays.

  • Thankfully, our planet's magnetic field blocks most of it, but out in the vastness of space,

  • there's not really anything to shield us against its effects.

  • Previous studies in mice have shown that exposure to heavy-ion radiation can lead to damaged

  • brain tissue and accelerated aging during prolonged space trips.

  • And this new paper only adds to the list of potential concerns.

  • In the study, researchers exposed mice to low doses of iron radiation, a form of heavy-ion radiation,

  • to simulate the exposure astronauts would receive during a round trip to Mars.

  • Then, these animals were compared to other groups of mice,

  • one which had been exposed to similar amounts of gamma rays,

  • and a control group that received no radiation at all.

  • The goal was to isolate the effects of different types of cosmic rays.

  • And what the team found wasn't that encouraging.

  • The mice exposed to iron radiation developed cancerous polyps in the soft tissues of

  • their GI tracts, and had fewer enzymes needed for nutrient absorption.

  • This may have happened if the radiation damaged the DNA in their intestinal walls,

  • making them incapable of normal cell division.

  • Now, it is worth noting that not all mice studies translate perfectly to humans,

  • especially when it comes to radiation.

  • But since we don't have a good way to protect our spacecraft against these kind of rays,

  • it's worth studying them any way we can.

  • Right now, good shielding materials are just too heavy to get into space,

  • and scientists are a long way from making an anti-cosmic radiation medicine.

  • As people get more serious about going to Mars, though, researchers are looking into every possibility.

  • These kind of studies are good reminders that space exploration is more than just

  • building big rockets: We also need to learn how to take care of the people on board.

  • But someday, when we're walking around on Mars or maybe even Planet 9, it will all be worth it.

  • Thanks for watching this episode of SciShow Space News!

  • If you'd like to help us make more episodes like, you can go to patreon.com/scishow.

  • And to all of our current patrons, thank you!

  • Our team couldn't do all of this without you.

  • [♪ OUTRO]

[♪ INTRO]

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第9惑星に新たな証拠が!| サイショウニュース (New Evidence for Planet 9! | SciShow News)

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    林宜悉 に公開 2021 年 01 月 14 日
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