Voyager-2
Welcome to my blog "Mystery of Galaxy". On November 5th 2018, Voyager 2 left the protective bubble of the Sun and joined its sister ship Voyager 1 on an interstellar mission 41 years after it launched. Voyager2 became just the second spacecraft ever to reach interstellar space. But to really put its achievement into perspective, we need to wind the clock back all the way to 1977 when Voyagers 1 and 2 were launched from Cape Canaveral. Their mission was unprecedented; a grand tour of the outer solar system. Interestingly, Voyager 1 actually launched about a month after Voyager 2.
 |
| Voyager-2 Source: CreeD93 / CC BY-SA |
But because Voyager 1 by that time was on an inside orbital track, it was able to overtake Voyager 2 and reach Jupiter first, hence the name "Voyager 1". Both spacecraft flew past Jupiter and its moons in 1979, then Saturn and its moon system in 1980 and 1981. Following the Saturn encounter, Voyager 1 accelerated upwards and out of the plane of the solar system while Voyager 2 would continue on to fly past Uranus in 1986 and Neptune in 1989. As both space craft raced toward the outer reaches of the solar system, they were still well inside of the heliosphere.
 |
| Heliosphere Source: Judith Nabb / CC0 |
The heliosphere is like a giant protective bubble created by charged plasma particles blowing out from the Sun. This stream of particles is called the solar wind, and it surrounds the Sun and most of the planets of the solar system. The solar wind races out at 2 million kilometers per hour, far beyond the orbit of Pluto, until it slams into the oncoming interstellar wind. This forms a boundary called the heliopause, which separates the heliosphere from the interstellar medium. As luck would have it, both spacecraft happened to be racing toward the leading edge of a heliopause. Along the way, Voyager 2 was able to monitor the solar wind using its plasma science experiment, or PLS. Voyager 1 also carried its own PLS system, but it failed back in 1980.So Voyager 2 gave scientists an opportunity to directly monitor the solar wind all the way out to the heliopause.
On November 5th 2018, Voyager 2 detected a sharp drop-off in solar wind particles, while at the same time detecting a sudden increase in
galactic cosmic rays. Cosmic rays are highly energized protons that move at extremely fast speeds and pack a lot of energy. The cosmic rays reaching the Voyager spacecraft were forged and accelerated in the supernova explosions of massive stars 10 to 20 million years ago. The sudden increase in cosmic rays, coupled with the sudden decrease in the solar wind, was proof that Voyager 2 had joined its sister ship in interstellar space. Now both spacecraft find themselves in the local interstellar cloud, which is about a hundred thousand times larger than the heliosphere. But this cloud is really thin - about a hundred trillion times less dense than the clouds in our atmosphere. Our Sun is moving through this cloud and that's why the heliosphere is shaped much like a comet. But with Voyager 2's working plasma detector, we may be able to learn whether or not the Sun has already left the local cloud or if it has in fact transitioned into the neighboring G cloud. This will help us to literally understand our place in the galaxy! Both spacecraft are still functioning and will continue to work for as long as they have the power to do so. Both spacecraft are powered by radioisotope thermal generators, which is simply a block of radioactive plutonium that decays overtime. As the plutonium decays, it generates heat which can then be used to power the rest of the spacecraft systems. However, as the plutonium decays, its power output weakens. Today, both spacecraft are transmitting with a power output of about 20 watts. That's the same amount of power generated by your refrigerator's light bulb. By the time that signal reaches Earth, it is already weakened to one ten-trillionth of a billionth of a watt. To conserve power, Voyager 2's onboard camera systems were deactivated following its flyby of Neptune in 1989. Still, the overall power output of both spacecraft continues to diminish by about 4 watts every year. This means that mission managers are gonna have to make some decisions as to what other instruments they can turn off in order to extend the Voyager interstellar mission.
galactic cosmic rays. Cosmic rays are highly energized protons that move at extremely fast speeds and pack a lot of energy. The cosmic rays reaching the Voyager spacecraft were forged and accelerated in the supernova explosions of massive stars 10 to 20 million years ago. The sudden increase in cosmic rays, coupled with the sudden decrease in the solar wind, was proof that Voyager 2 had joined its sister ship in interstellar space. Now both spacecraft find themselves in the local interstellar cloud, which is about a hundred thousand times larger than the heliosphere. But this cloud is really thin - about a hundred trillion times less dense than the clouds in our atmosphere. Our Sun is moving through this cloud and that's why the heliosphere is shaped much like a comet. But with Voyager 2's working plasma detector, we may be able to learn whether or not the Sun has already left the local cloud or if it has in fact transitioned into the neighboring G cloud. This will help us to literally understand our place in the galaxy! Both spacecraft are still functioning and will continue to work for as long as they have the power to do so. Both spacecraft are powered by radioisotope thermal generators, which is simply a block of radioactive plutonium that decays overtime. As the plutonium decays, it generates heat which can then be used to power the rest of the spacecraft systems. However, as the plutonium decays, its power output weakens. Today, both spacecraft are transmitting with a power output of about 20 watts. That's the same amount of power generated by your refrigerator's light bulb. By the time that signal reaches Earth, it is already weakened to one ten-trillionth of a billionth of a watt. To conserve power, Voyager 2's onboard camera systems were deactivated following its flyby of Neptune in 1989. Still, the overall power output of both spacecraft continues to diminish by about 4 watts every year. This means that mission managers are gonna have to make some decisions as to what other instruments they can turn off in order to extend the Voyager interstellar mission.
Even though both spacecraft have reached interstellar space, they have along way to go before they actually leave the solar system. Voyagers 1 & 2are 144 and 120 astronomical units from the Sun. One astronomical unit is the distance from the earth of the Sun, and Neptune is about 30 astronomical units from the Sun. So both spacecrafts are 4 and 4.8 times farther from the Sun than Neptune. That's far, really far! But starting at 1,000 astronomical units is the Oort cloud, a giant sphere of small icy comet nuclei that silently orbit the Sun over millions of years.
 |
| Oort clouds Source: Translated into Telugu by User:Mekala Harika / CC0 |
It will take the spacecraft about 300 years to reach the inner edge of the Oort cloud, and then another 30,000 years to emerge from the other side. By that point, both spacecraft will be more than a light-year from Earth, and will have left the outermost fringes of the solar system behind. Their ultimate destinies are to orbit the Milky Way among its 400 billion stars. But even then, Voyagers 1 & 2 will carryon with one final ultimate mission. Each spacecraft carries a golden record with music, sounds, images, and greetings in 55 languages from the people of planet Earth. They are humanity's message in a bottle, carrying with them a record from a long-extinct civilization that was once curious enough to explore the universe surrounding it. Thank you for reading.
Excellent read. Thanks!
ReplyDelete