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When you look at the night sky, you can see thousands of stars using nothing but your | |
eyes, far from the lights of cities. | |
In fact, there are many more stars in the sky which are too faint for us to see. | |
Every single star that you can see is a part of our Milky Way galaxy, our heavenly home | |
that has captured people's attention for ages. | |
The shimmering band of stars, dust, gas and dark matter that makes up the night sky captures our attention. | |
These elements are all held together by gravity. | |
As we navigate through the cosmos, an intriguing enigma emerges. | |
What is the Milky Way truly like? | |
What makes it up? And where does our solar system exist in the Milky Way? | |
Astronomers have been baffled by these fundamental questions for many centuries, and finding answers was no easy task. | |
But beyond its luminous beauty lies a tapestry of mysteries waiting to be unraveled. | |
Join us today as we embark on an amazing adventure around the Milky Way uncovering its mysteries, wonders and majesty. | |
You are probably somewhat familiar with our solar system. | |
You are probably somewhat familiar with our solar system. | |
If nothing else, you probably already know that it contains eight planets in addition to | |
the Earth, the Sun, moons and several other celestial bodies like asteroids and Pluto. | |
However, there is a lot more beyond the solar system of which you may not be aware. | |
From Earth, we can see roughly 6,000 stars without the use of a telescope. | |
Even while that seems like a large number of stars, it represents a very small portion of the total. | |
In fact, for every star you can see, there are more than 20 million you cannot see. | |
The majority of stars are either too dim, too far, or obstructed by clouds of cosmic dust. | |
While the Milky Way galaxy contains all of these stars, there are other, larger galaxies as well, including the Andromeda galaxy. | |
Every galaxy is a system made up of various stellar remnants, interstellar medium, and star systems. | |
Scientists believe there are 100 billion galaxies in the cosmos, yet they are not sure. | |
Intergalactic space, which contains a thin gas, lies in between the galaxies. | |
Given the size of our solar system, and the fact that it is only one of many in our galaxy, it is understandable why the universe is thought to be infinite. | |
This truly helps to put into perspective how tiny both Earth and humans are in the big picture. | |
Through the use of radio and X-ray telescopes, scientists have been able to gather information | |
during the past century about the composition of the interstellar medium. | |
They have shown that it is made up of extremely diffuse ionized hydrogen atoms, dust, and cosmic | |
rays scattered throughout thick gas clouds that are thought to be the birthplace of new stars. | |
But because of the Sun, all eight planets, and a far-off disk of debris known as the Kuiper Belt, | |
its precise nature just outside our solar system has remained mostly unknown. | |
The Kuiper Belt is located between 30 and 50 astronomical units from the Sun. | |
One astronomical unit is equivalent to the distance between Earth and the Sun. | |
The heliosphere, a massive protective bubble created by the solar wind, surrounds them all. | |
This bubble buffets against the interstellar medium like an invisible shield, keeping out most | |
dangerous cosmic rays and other material as the Sun and its surrounding planets hurtle across the galaxy. | |
Without the heliosphere, life would certainly have evolved differently and maybe not at all. | |
The area where the Sun's magnetic bubble ends and weakens is known as the interstellar space border. | |
The heliosphere, a magnetic bubble, is full of plasma or ionized gas. | |
The solar wind, which pulls magnetic field lines away from the Sun, blows material into the heliosphere. | |
With its own magnetic fields and charged particles, the plasma in the interstellar medium exerts | |
an inward push on the heliosphere's edge, creating a complex and dynamic structure there. | |
When the solar wind encounters interstellar space, it begins to weaken and slows to approximately 62 miles per hour. | |
It was previously traveling between 370 and 430 miles per hour. | |
The termination shock is the point at which this happens. | |
The heliosheath is the area in the heliosphere where the solar wind continues to slow down | |
after the termination shock, while the heliopause is the outermost point of the heliosphere. | |
The solar wind stops and gives way to interstellar space at the heliopause, which is located around | |
11 billion miles or 18 billion kilometers from the Sun. | |
Five, four, three, two, one. We have ignition, we have a liftoff. | |
Since the beginning of human space exploration, only two probes have made it to interstellar | |
space, or the area outside of the solar system. | |
After launch in 1977, Voyager 1, the first spacecraft, took more than 30 years to reach | |
the heliopause, a limit that scientists believe marks the beginning of interstellar space. | |
It was an amazing accomplishment, sending back vital information via a medium unaffected by the Sun. | |
As we exit the solar system, we will reach Alpha Centauri. | |
The triple star system, which is the closest star system to Earth, located at about 4.37 | |
light years away in the constellation Centaurus. | |
It is a triple star system consisting of three stars, Alpha Centauri A, Alpha Centauri B, and Proxima Centauri. | |
Alpha Centauri AB is a binary star system made up of Alpha Centauri A and B, which are Sun-like | |
stars, classified as class G and K respectively. | |
These two main stars have an apparent magnitude of minus 0.27, making them appear to be a single | |
star to the unaided eye. | |
Only Sirius and Canopus are brighter than it, making it the brightest star in the constellation and the third brightest in the night sky. | |
Alpha Centauri B is smaller and colder than Alpha Centauri A, with 0.9 solar mass and less | |
than 0.5 solar luminosity. | |
While Alpha Centauri A has 1.5 times the luminosity and 1.1 times the mass of the Sun, the two have | |
a 79-year orbital period around a shared center. | |
The distance between A and B fluctuates from 35.6 astronomical units, or roughly the distance | |
between Pluto and the Sun, to 11.2 AU, or roughly the distance between Saturn and the Sun, due | |
to the eccentricity of their elliptical orbit. | |
In the Alpha Centauri system, Proxima Centauri is the star nearest to the Sun, located approximately 4.2 light-years from Earth. | |
Robert Innes, a Scottish astronomer, made the discovery of the star in 1915. | |
Proxima Centauri is a red dwarf star, which is the most common kind of star. | |
It is roughly seven times smaller than the Sun, and a little more than half as hot at 3,100 kelvins. | |
On the other hand, our Sun is 5,772 kelvins. | |
As a matter of fact, this little star is just 50% larger than Jupiter. | |
Red dwarf stars have long lives because they consume hydrogen fuel very efficiently. | |
Proxima Centauri is expected to remain in its current state for more than 4 trillion years. | |
The Alpha Centauri system can be seen in the constellation Centaurus, Proxima Centauri is usually | |
not visible to the human eye. Proxima Centauri orbits the other two stars in the system, | |
Alpha Centauri A and B. Proxima Centauri takes 550,000 years to complete an orbit of A and B. | |
With an apparent visual magnitude of 11, Proxima Centauri is the dimmest of the three stars. | |
This star emits light at a slower rate than the Sun, with a luminosity of 0.17% that of the Sun. | |
However, Proxima Centauri is categorized as a flare star, which is prone to massive solar flares, | |
because its brightness can vary by more than one magnitude in a matter of minutes. | |
These flares, which occur multiple times a day, have the potential to be powerful enough to make Proxima Centauri visible to the human eye. | |
The greatest solar flare ever observed in the Milky Way galaxy was released by Proxima Centauri in 2019, | |
glowing 14,000 times brighter in ultraviolet wavelengths than normal. | |
Even though Proxima Centauri will live longer than the Sun, it will eventually meet the same fate. | |
Proxima Centauri will end up as a burning white dwarf star, because it does not have the mass | |
to turn into a neutron star or a black hole when its hydrogen supply runs out. | |
As of 2022, astronomers have detected three planets orbiting Proxima Centauri, | |
Proxima Centauri BC and D. These are the closest planets outside the Solar System. | |
Red dwarf stars are small and cool, thus planets can circle quite close to them and still be classified as being in the habitable zone. | |
This is the range of distance from a star where a planet's water, if any, could be liquid and potentially support life. | |
Proxima Centauri b was discovered in 2016 and estimated the planet to contain about 17% |
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