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00:00Up to Neptune, the solar system has a diameter of about 5 billion miles.
00:06Up to the Oort cloud, it's more than 5 trillion miles.
00:10But once you break out of it, there's so much more to explore.
00:14The Milky Way hosts upwards of 200 billion other star systems.
00:21So where are you going first?
00:27What exactly constitutes a solar system?
00:29Well, aside from the obvious requirement of a star, a solar system consolidates more than
00:33just planets revolving around a ball of hydrogen and helium.
00:37Anything influenced by the star's gravitational pull is part of the system, and this includes
00:41asteroids, comets, meteoroids, and natural satellites.
00:45Estimated to be more than 4.5 billion years old, our sun breathes life into the wider
00:50solar system.
00:51While our corner of the universe is big enough to keep NASA busy for the foreseeable future,
00:56it's but one sliver of a larger galaxy known as the Milky Way.
01:00Technically, to us, there is only one solar system, as other clusters are referred to
01:04as stellar or star systems, but estimates suggest that there are approximately 200 billion
01:09stars in the Milky Way.
01:11The galaxy's almost incomprehensible size puts things into perspective, but the Milky
01:15Way is merely one small town.
01:17In fact, the Hubble Telescope has established the existence of at least 100 billion galaxies.
01:23So, how exactly is the universe structured?
01:26If someone were to leave the solar system, would they soon encounter a new collection
01:29of planets orbiting another ball of fire?
01:31Eventually, possibly… but not before some serious voyaging.
01:36Collectively known as the interstellar medium, the space separating star systems begins where
01:40a sun's magnetic field stops influencing its surroundings, and it chiefly consists
01:44of gas and dust.
01:46Because, regardless of what it seems, space isn't truly a vacuum, although the density
01:50varies wildly from area to area.
01:53In the grand scheme of things, the solar system is miniscule.
01:56Nevertheless, human ingenuity has yet to advance far enough to allow for a safe voyage into
02:00interstellar space.
02:02Due to the vast distances being calculated, we use astronomical units to actually measure
02:07space, with one AU equivalent to the average gap between Earth and the sun, which is approximately
02:1293 million miles.
02:14Entering into only the first stretch of interstellar space means travelling farther than 120 AU,
02:20and even then the sun's gravitational pull continues to wield some effect for roughly
02:24another 100,000 units.
02:26Given that humans have made it to the moon but no further, with trips to other planets
02:30still seeming a far-off dream, getting people into interstellar space seems an impossible
02:34goal.
02:35However, while a manned shuttle isn't currently on the cards, two spacecraft have successfully
02:40crossed into the interstellar, Voyager 1 and 2.
02:43Launched in 1977, Voyager 1 has been flying away from the sun towards the great unknown
02:48for decades.
02:49After completing its primary mission by 1980, conducting flybys of Jupiter, Saturn and Titan,
02:55it just kept going and going… until, in 2012, it became the first human-made spacecraft
03:00to enter the interstellar medium.
03:02Six years later, Voyager 2 repeated the same staggering feat, although it's important
03:07to note that even these crafts have only actually left the heliosphere, which is essentially
03:11a bubble created by the sun's solar wind, and not the entire solar system itself.
03:16Using Voyager 1 and 2 as blueprints, it'd take more than 30 years to travel the 11 billion-odd
03:22miles necessary to reach the interstellar medium… but that's assuming the human
03:26body could somehow withstand the 38,000 miles-per-hour velocity sustained by Voyager 1.
03:31Say science does find a way for humans to complete such a journey, though… what sights
03:36can an astronaut look forward to?
03:38Putting aside the technological process needed to amass the necessary momentum to actually
03:42leave the solar system, the route involves crossing the asteroid and Kuiper Belts towards
03:46the heliosphere's outer layer.
03:48Ranging from Mars to Jupiter, the asteroid belt is unsurprisingly home to the majority
03:52of the solar system's asteroids.
03:55With the number of drifting stones in the thousands, you might think that this portion
03:58of the journey would coincide with quite a bit of turbulence… but, luckily, the asteroids
04:02are dispersed over such a massive area that avoiding a direct hit should be fairly simple.
04:07The Kuiper Belt covers the area past Neptune and, alongside other dwarf planets, includes
04:12Pluto.
04:13Like its predecessor, the Kuiper is sparsely littered with floating objects, although many
04:17tend to be frozen due to the sun's weakening rays once you get this far out.
04:21Following the belts, the spacecraft steadily begins to approach the heliosphere's outer
04:25layers.
04:26On average, Pluto is around 40 AU away from the sun, but the heliosphere stretches on
04:30for another 80 units.
04:32It's essentially a protective bubble created because our star exudes charged particles
04:36as solar wind, and the heliosphere is how far they stretch.
04:40Beyond this point, the sun does continue to exert a force on objects, but the particles
04:44are less densely packed, and the bubble breaks up… which takes us to perhaps the first
04:49significant roadblock on this ultimate road trip… a stream of gas known as the Termination
04:53Shock.
04:54This layer coincides with the sun's solar wind colliding with the interstellar wind
04:58on the other side.
04:59It's where the sun's influence truly starts to diminish.
05:03According to NASA, Voyager 1 crossed this threshold at approximately 94 AU.
05:08The Termination Shock leads into the heliosheath, which is the heliosphere's outermost layer.
05:13Theoretically, this area should be the most volatile of the lot, marking the point when
05:17the interstellar wind begins to match the sun's power, making conditions almost impossible
05:21to predict.
05:22Picture the solar system as a boat sailing across a sea of gas, and the heliosheath is
05:27the bow thrusting against the waves, taking most of the force.
05:31Finally, we reach the heliopause, which is the final, final border separating the heliosphere
05:35and interstellar space.
05:37At this point, the solar and interstellar winds emit equal but opposing pressures, causing
05:42the sun's particles to flip inwards towards their source of origin.
05:45It's a point of no return for most of anything linked to our solar system.
05:49With the heliopause in the rearview mirror, astronauts can look forward to drifting through
05:53empty, seemingly endless space before ultimately entering the solar system's true final layer,
05:59the Oort Cloud.
06:00Believed to consist of comets requiring approximately 200 years to orbit the sun, astronomers believe
06:05the Oort Cloud commences at a distance of 1,000 astronomical units from the sun and
06:10stretches on for approximately 100,000 units.
06:13If Voyager 1 required 35 years to leave the heliosphere, the spacecraft has to continue
06:17moving forward at the same speed for roughly another 250 years to reach the Oort Cloud.
06:23By now, assuming that we A, somehow had the technology to take us this far, and B, had
06:27devised some way of stalling our natural ageing process so that we're still alive by the
06:31time we break the Oort Cloud, our minds and bodies will have gone through some major transformations.
06:36Earth's atmosphere protects against the sun's radiation, and an astronaut's body
06:41tends to weaken after only a couple of months away from the planet's surface.
06:44So, in reaching the heliopause, astronauts would risk exposure to an immeasurable amount
06:49of radiation over an incredible time period.
06:52Even with some kind of radiation immunity medicines or technologies, and even though
06:56they would be steadily moving away from the sun, any interstellar astronaut will have
07:00had to have gone some form of adaptation to their surroundings.
07:04Throw into the mix infinitely heightened concerns over muscle atrophy and bone mass decline,
07:08inevitable challenges regarding mental health and unknowable problems linked with the endless
07:13isolation, and you end up with a traveller almost unrecognisable from that which had
07:17set off.
07:18Assuming you somehow managed to enter interstellar space in one piece, the Oort Cloud should
07:22take around 30,000 years to traverse.
07:25Of course, the painstaking commute could be avoided if we managed to develop a viable
07:29method of travelling at light speed.
07:30In fact, taking into account that the sun's rays need a bit more than eight minutes to
07:34hit Earth, a shuttle travelling at the speed of light should be able to leave the entire
07:38solar system in less than 600 days.
07:41Whichever way you get there, with the solar system finally behind you, the question becomes
07:45what's next?
07:46The Alpha Centauri system is adjacent to ours and houses three stars, with the red star
07:51Proxima Centauri being the closest.
07:53So, that would be your next port of call.
07:56But here's hoping you're not running low on fuel and you're still somehow keeping
07:59old age at bay… because getting there, even at light speed, would take another four years.
08:05Travel at anything less than light speed, and you're talking centuries.
08:08What would you see on the way?
08:10Unsurprisingly, we're low on first-hand accounts, but the light from Proxima Centauri
08:14would always be in your sights, growing brighter day by day.
08:17If humans ever were headed that way, then chances are they'd be bee-lining for the
08:22exoplanet Proxima Centauri b, as it's the closest exoplanet to us and it orbits within
08:27a potentially habitable zone.
08:29So, if there's life outside of our solar system, then here would be a good bet to host
08:33our closest neighbours.
08:35And from there, if we've advanced enough as a species to survive such a monumental
08:38trip, then the entire universe is ours to explore.
08:42The Milky Way is, after all, simply one member in a cluster of large and dwarf galaxies.
08:47Andromeda is the nearest similarly-sized galaxy to ours.
08:51So, if we ever could go galaxy-gallivanting, then we'd wind up in Andromedan territories
08:55next.
08:56That said, Andromeda is estimated to be around 2.5 million light-years away from us, so we'd
09:02have to improve on even light-speed travel to stand even a slim chance of seeing it.
09:06Right now, it feels like the farthest of far-off dreams.
09:10What do you think?
09:11Is there anything we missed?
09:12Let us know in the comments, check out these other clips from Unveiled, and make sure you
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