Scientists have discovered that, far in the future, our Sun will go through a massive transformation! Right now, it's a stable star in the middle of its life, but billions of years from now, it will start to run out of fuel. As this happens, it’ll expand into what’s called a "red giant," growing up to 300 times its current size! This means it could become so big that it might swallow up the planets closest to it, like Mercury, Venus, and possibly even Earth. The Sun’s outer layers will drift away, creating a beautiful shell of glowing gas called a planetary nebula. Eventually, it’ll shrink back down to a small, cool star called a white dwarf, ending its long life as a faint point of light.
00:00A recent study has involved almost 200 huge stars that are reaching the end of their lives.
00:07It has given scientists more precise information about how the Sun will one day end.
00:12It turns out that the Sun will be about 200 to 300 times bigger than it is now by the time its game is over.
00:21For starters, let's begin with some basic information about star sizes.
00:26Giant ones reach this stage because they've run out of nuclear fuel and are no longer burning hydrogen in their core.
00:33Eventually, the core gets hot enough to trigger the next stage of fusion, which is helium burning.
00:39All the stars that were surveyed in this new study were either in this hydrogen shell burning or helium core burning phase.
00:48Even though giant and supergiant stars only make up less than 5% of all stars,
00:54or at least that we know of, they're actually really visible from a distance because they're so bright.
01:01In fact, according to scientists, about a third of all the stars you can see outside on a dark moonless night are giant or supergiant stars.
01:11This study will eventually give astronomers really useful info about massive stars.
01:17They'll be able to figure out their size and temperature no matter where they are or their evolutionary stage.
01:23This means they can see a star's true color and use that to find out its radius.
01:29Pretty cool, right?
01:31It does raise the question, what will our sun be like when it gets old and grumpy?
01:37To put it simply, it will expand when it starts burning its hydrogen shell,
01:42but then shrink a bit during its helium core burning phase.
01:45After a few hundred million years, it'll end up as a giant star, about 200 to 300 times its current size.
01:54Eventually, the sun will expand so much that it will simply evaporate.
01:59So, what will happen after the sun fades away?
02:03Scientists actually have some predictions about what will go down, even though we won't be around to see it.
02:09They're pretty sure the sun will turn into a planetary nebulae.
02:14These planetary nebulae are chunks of gas and dust in space that come from a star that is fading away.
02:21They got their name because they looked like planets to people using telescopes back in the 18th century,
02:28even though we now know they have nothing to do with actual planets.
02:32And here's the crazy thing.
02:35Astronomers have found out they can use the level of brightness of these planetary nebulae to calculate their distance from us.
02:42In 2018, scientists also found out that the sun is the smallest a star can be to still be able to produce a visible nebula.
02:51Any smaller, and it would not be visible.
02:54Stars that are up to three times more massive than the sun will produce brighter nebulae.
02:59The sun is currently 4.6 billion years old, but it's estimated to have another 10 billion years until its end.
03:09The sun is also getting brighter with each year.
03:13It doesn't seem like a lot now, but it's actually going to cause some big problems for Earth.
03:19In about a billion years, the sun will be too bright for life on Earth to survive.
03:24Our oceans will evaporate, and it will be too hot for water to form again.
03:30So unless we find a way to escape from this planet, humanity only has about a billion years left.
03:37Will Earth still be around by the time the sun turns to dust?
03:42It's hard to know for sure the exact timeline.
03:45But even before that happens, Earth will most likely be scorched and lifeless, with no atmosphere or oceans left.
03:52It's not clear how close the sun's outer layers will get to Earth.
03:57But if they get too close, it could cause Earth to spiral into the sun and disappear altogether.
04:03Even if our planet does somehow manage to survive the sun's giant phase, it will be orbiting a hot white dwarf, or a star that has run out of its fuel.
04:15In that distant future, the sun will be barely larger than our planet.
04:21Eventually, the sun will cool and dim completely.
04:24It'll move to another stage called a black dwarf.
04:26It will cause Earth's orbit to loosen up, and our planet will spiral into the faded sun.
04:33But interestingly, the sun doesn't get the final say in what happens to Earth.
04:38Gravity keeps planets in orbit, but it also attracts them to each other, which can cause their orbits to flex and drift.
04:46This could lead to the solar system destabilizing and ejecting planets, including Earth.
04:52Basically, a lot might happen in the next 5 billion years before the sun becomes a red giant.
04:59There's also another scenario.
05:03While most stars stay far away from our solar system,
05:05there's a chance that one could come closer in the next billion years.
05:11Even a small star or black hole could mess up the orbit of our planet if it gets too close.
05:17But don't worry too much.
05:18The odds of that happening are low because of the amount of space between stars.
05:24Our sun is a solitary star,
05:26so there's little to no chance we'll be able to catch a ride with another one nearby.
05:32However, many stars in our universe have companions.
05:35Among these stars is Castor,
05:37a stunning system that comprises six stars
05:40and is one of the brightest objects in the night sky.
05:45Although humans have been admiring Castor for ages,
05:48they were not aware of its true nature until the invention of telescopes and spectroscopes.
05:54Even with the help of a small telescope,
05:57it's evident that Castor is composed of two primary stars,
06:01Castor A and B-A,
06:02that revolve around each other.
06:04These stars are larger than the sun and need 467 years to complete one orbit.
06:12In total, Castor is composed of six different stars.
06:16The biggest one, called Castor A-A,
06:18is roughly two times larger than the sun,
06:21while the smallest has about 0.5 of the sun's mass.
06:25If humans want to survive the next billions of years,
06:29we might need to set up camp somewhere else in the universe.
06:33It may seem like something out of a sci-fi movie,
06:35but it could be our reality one day.
06:38Thankfully, NASA is already looking at some options.
06:42They've discovered two new planets,
06:45TOI-700E and TOI-700D.
06:49That might be new hotspots for us humans.
06:53TOI-700E is the optimistic zone,
06:56which means it could have water and even an atmosphere.
07:00TOI-700D is in the conservative habitable zone.
07:04So, scientists aren't too sure about it yet,
07:07but hey, we'll take what we can get.
07:10But hold on.
07:11Before you start packing your bags,
07:13there's a little problem.
07:15How do we get there?
07:16It took John Glenn months of preparation
07:19just to circle Earth three times.
07:22So we might need to start working on our astronaut training.
07:26Well, at least we have some options
07:28for our future intergalactic vacation plans.
07:32Wouldn't it be nice if we could time travel
07:34so we could see what our solar system
07:35will look like in billions of years?
07:38An American physicist named Ron Mallet
07:40has proposed one interesting theory for time travel.
07:44It uses light,
07:45a resource that is abundant in the universe.
07:48His idea involves using a rotating cylinder of light,
07:51which could transport an object in both space and time,
07:55similar to how a bubble moves in a swirling liquid.
07:59Mallet suggests that a cylinder of the right shape
08:02could allow for travel to the past and the future.
08:05To test his theory,
08:07he has been trying to secure funding for an experiment.
08:10However, some scientists consider Mallet's theory
08:12to be impossible and unnecessary to test.
08:16We might also be able to travel through time
08:19if we move fast enough.
08:21According to Einstein,
08:22the way we experience time can change
08:24depending on how fast we're moving.
08:27If we go really fast,
08:29time slows down.
08:30For example,
08:31astronauts in space
08:32age a tiny bit more slowly
08:34than people on Earth.
08:36This is important for things like GPS,
08:39which would be incorrect without special adjustments
08:41because of how time is affected.
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