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  • {♫Intro♫}

  • Stars explode and die all the time, but they're so faint and far away that on Earth, we rarely

  • notice.

  • Dying stars we can see with the naked eye are few and far between.

  • Luckily for us, though, three astronomers announced at the American Astronomical Society

  • meeting last week that in not too long, we're in for a treat.

  • They found that, as early as the 2060s, two stars are going to merge, and that event will

  • be so bright that we'll be able to see it with the naked eye!

  • The 2060s might seem like a long way off for us mere mortals, but it will definitely be

  • spectacular.

  • Because this explosion won't be your typical supernova.

  • It will be something completely new to us.

  • The system is called V Sagittae.

  • It's roughly 7800 light-years from here, and it's classified as a Cataclysmic Variable,

  • or CV.

  • That means it's a binary star system made of a relatively Sun-like star and a white

  • dwarf.

  • That's the leftover core of a star that wasn't massive enough to undergo a supernova

  • at the end of its life.

  • And these two objects are close enough that the white dwarf's gravity pulls matter off

  • its companion, stealing it and gaining mass as a result.

  • In normal cases, these systems are mind-boggling.

  • Because eventually, the gluttonous white dwarf will steal so much matter that it either explodes,

  • or its outer layer gets blasted into space.

  • But V Sagittae is special.

  • It's the only CV we know of whose white dwarf is less massive than its companion.

  • About four times less massive, too.

  • This imbalance causes some weird effects, but ultimately, it means the stars in this

  • system aren't in a stable orbit.

  • They're spiraling toward each other, and eventually, they're going to collide.

  • Recently, this team analyzed data about the system's light and position going back to

  • 1890.

  • And they confirmed V Sagittae is in the middle of this death spiral, and that somewhere between

  • 2067 and 2099, the two objects will officially merge.

  • That will create a new light in our night sky for more than a month!

  • Right now, this system is too dim to be visible.

  • But during that month, it will be as bright as Siriusthe current brightest star we

  • can see after dark.

  • And it could even briefly be as bright as Venus, the brightest night-time object besides

  • the Moonor the International Space Station, depending on the timing.

  • When it's all over, this system will end up as a single star, and it's not clear

  • if we'll be able to see it without a really fancy telescope.

  • So most of us might not have long to see this for ourselves.

  • But whatever time we /do/ have will still be amazing.

  • Of course, while 80 years is barely a blink of an eye on cosmic time scales, 2099 is pretty

  • far away

  • So, here's hoping that merger happens sooner rather than later.

  • Because, let's be honest: I'd really like to be around to see it.

  • While we wait for the future to arrive, though, let's take a moment and look back to the

  • past.

  • Because this Monday in the journal PNAS, scientists announced the oldest solid matter ever found

  • on Earth.

  • It's a compound called silicon carbide, and it formed hundreds of millions of years

  • before our solar system was born.

  • And, as if that weren't cool enough, it also gives astronomers some clues about our

  • galactic history.

  • Most of the solids in our solar systemthings like dust and rockscondensed from gas

  • about 4.6 billion years ago, about the time the Sun formed.

  • But a tiny percent of dust was already there, just hanging out.

  • Astronomers call them presolar grains, but you'll sometimes hear the more poetic term

  • stardust”.

  • That's because they formed in the outer atmospheres of red giant stars in the last

  • stages of their lives.

  • As the stars died and shed their outer layers, the grains entered interstellar space and

  • got struck by cosmic rayshigh-energy, charged particles.

  • That caused reactions that changed the elements the grains were made of.

  • Eventually, these tiny pieces wandered into our neighborhood.

  • When our solar system started forming, some of them got encased by new solid matter, which

  • protected them against further damage and the effects of time.

  • While a lot of that matter went on to form planets, plenty was left over, free to hit

  • Earth in the form of meteorites.

  • And so, billions of years later, we've started finding them.

  • Presolar grains are really rare and tinytypically a few millionths of a meter in size.

  • But they do turn up.

  • The meteorite containing these record-breaking grains landed in Australia back in 1969.

  • And recently, scientists took a fragment of that space rock, crushed it up, and used acid

  • to dissolve all but the silicon carbide grains.

  • Then, they calculated the age of those grains by measuring how much of a special isotope

  • of neon they contained.

  • That amount determined how long the grains had been exposed to cosmic rays before getting

  • sealed up.

  • Most of the pieces had traveled through space for less than 300 million years before being

  • incorporated into the early solar system.

  • So, that would put them around 4.9 billion years old at most.

  • But a few other pieces had traveled for more than a billion years.

  • Making them more than 5.5 billion years old.

  • It's those little guys that set the record for the oldest solids on the planet.

  • But don't get me wrong: Those younger grains are important, too.

  • Their abundance supports the hypothesis that our galaxy's production of stars isn't

  • constant.

  • That there was a surge in star formation about seven billion years ago that produced the

  • stars needed to create these grains.

  • And that's important, because researchers are still trying to figure out what star formation

  • has looked like over time.

  • And these grains could help them learn more.

  • So it's nice to know you can be important without having to break records.

  • Excellent motivational message, universe!

  • Thanks for watching this episode of SciShow Space News!

  • Before you go, we wanted to let you know that our pin of the month is currently available!

  • This month, it's celebrating Explorer 1, the first satellite the U.S. ever launched

  • into space!

  • We've come so far.

  • The pin is pretty rad, but it's only available during the month of Januaryso if you

  • want one, you've only got a couple weeks left.

  • To check it out, you can go to DFTBA.com/scishow or find the pin in the merch shelf below.

  • Thanks

  • {♫Outro♫}

{♫Intro♫}

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準備好迎接夜空中的新星吧!| 科學秀新聞 (Get Ready for a New Star in the Night Sky! | SciShow News)

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    林宜悉 發佈於 2021 年 01 月 14 日
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