Compared with Voyager 1, Voyager 2 has been almost forgotten. Where is it now?

Voyager 1 and 2 are a pair of sister probes, so please don't be offended if they are referred to as human beings in this article.

As the eldest sister, Voyager 1 is the fastest and farthest flying probe among the five probes currently flying into deep space outside the solar system. Therefore, it has received countless focus and attention. However, the younger sister Voyager 2 has always been hidden in the light of its older sister and has been somewhat ignored or even forgotten.

Voyager 1 is now moving away from the sun at a relative speed of 16.9 kilometers per second, and is more than 23.3 billion kilometers away from us; while Voyager 2 is now moving at a relative speed of only 15.3 kilometers per second, and is 19.4 billion kilometers away from us. In fact, Voyager 2 was launched earlier, but is now lagging behind. Why is this?

Today we will learn about the experience of this almost forgotten little sister.

My sister left earlier

In fact, Voyager 1 and 2 were originally the follow-up of the Mariner Program, called Mariner 11 and 12. The Mariner Program launched Mariner 1 on July 22, 1962, and launched 10 Mariner probes, of which 3 failed and 7 succeeded. These probes explored Venus and Mars successively, and obtained a lot of information and photos of these planets for humans, which will not be elaborated here.

Perhaps NASA felt that space exploration had entered a new phase and the name Mariner was no longer suitable for the new mission, so the names of Mariner 11 and 12 were changed to Voyager 1 and 2. These two sister probes carrying out new missions will for the first time cleverly use the gravitational slingshot effect of giant planets to speed up and change their orbits in time, so as to achieve the purpose of exploring multiple planets and their satellites, and fly out of the solar system after completing the solar system exploration mission!

The reason for choosing 1977 for the launch was that in that year several gas giant planets in the outer solar system would be in a rare line, an opportunity that only occurs once every 175 years. Therefore, NASA scientists seized this opportunity to kill two birds with one stone: allowing the launched probe to borrow the gravity of the planets along the way, gain additional power and speed, and also to explore multiple planets at once.

The official reason for launching two almost identical sister probes at once is to be on the safe side.

Therefore, the configurations of the two detectors are almost identical, and they can be said to be twin sisters. They each weigh 815 kilograms and are equipped with 11 scientific instruments, including cosmic ray sensors, ultraviolet spectrometers, polarimeter subsystems, plasma sensors, magnetometers, wide-angle and narrow-angle television cameras, infrared interferometers, etc. The main power is three radioisotope thermoelectric generators, which can also be called nuclear batteries.

Voyager 1, which was originally scheduled to be launched first, had its launch delayed due to a malfunction, so Voyager 2 took the lead and was successfully launched on August 20, 1977, leaving the Earth; Voyager 1 was successfully launched on September 5, 1977, 16 days later than its sister.

So why did Voyager 1 come from behind and fly ahead of its sister?

Because the two sisters chose different flight methods and routes

In the solar system, Voyager 1 mainly explored the two planets Jupiter and Saturn, and then flew out of the solar system; its younger sister Voyager 2 explored the four giant planets Jupiter, Saturn, Uranus, and Neptune, and also explored several satellites of Jupiter and Saturn and Neptune's satellite Triton. Its exploration mission in the solar system is more than half that of its older sister.

Deep space probes are not like what some people imagine, aiming at a target planet and then flying straight to it. Since the Earth and the planets are in motion, the distance and position between them are constantly changing, so in order to find a fuel-saving and faster route, it is necessary to find a suitable launch window, and the route must be a curve.

The initial velocity after launch is different depending on the target of the probe. Generally, the initial velocity after launch is configured according to three cosmic velocities, that is, a satellite orbiting the earth is required to reach the first cosmic velocity, 7.9 kilometers per second; a planetary probe flying out of the earth's gravity is required to reach the second cosmic velocity, 11.2 kilometers per second; and a spacecraft flying out of the solar system is required to reach the third cosmic velocity, 16.7 kilometers per second.

However, if we only rely on these initial speeds, we will reach the target planet very slowly, because the probe flying to the far side of the solar system will be pulled slower and slower by the gravity of the sun. To increase the initial speed, the rocket needs to carry more fuel and become larger, which will not be worth the effort.

As a result, scientists have found a natural power that uses the gravity of the planet and does not require fuel - the gravitational slingshot effect.

The gravitational slingshot effect is that when a spacecraft approaches a giant planet, as long as the angle is right, the gravity of the planet can be used to eject the probe like a slingshot, gaining a faster speed. This is why in order to obtain this extra power, sometimes launching a spacecraft will take more detours, which in turn shortens the time to reach the target.

For example, some spacecraft will orbit the earth or even the sun several times, going in the opposite direction of the target planet, and then fly to the target planet after gaining acceleration, such as the Juno Jupiter probe.

The Voyager sister probe seemed to show the advantage of the older sister from the beginning. She caught up with the younger sister in December 1977, 16 days earlier. The detailed reason for the path was not found. The limited information only had a vague statement that the older sister was launched into a faster orbit, while the younger sister took a slower trajectory. It can be seen that from the beginning, the older sister had the advantage of route and speed.

But what they all ended up with was that they all gained gravitational slingshot acceleration at Jupiter. The older sister flew past Jupiter in March 1979, and her speed relative to the Sun increased from 14 kilometers per second when she arrived to 37 kilometers per second when she left; the younger sister flew past Jupiter in July 1979, and her speed increased from about 10 kilometers per second when she arrived to 35 kilometers per second when she left.

The younger sister follows in her elder sister's footsteps

The Voyager sister probes look similar and have almost the same functions. NASA launched these two similar probes for the sake of safety. So is the slower sister redundant? No. Because they take different paths, they each shine in their own way.

The elder sister probed only Jupiter and Saturn at a more efficient pace and speed. After sending back a large amount of data, it went into hibernation and headed straight out of the solar system. It was not until more than 30 years later that it was awakened and its auxiliary engine was adjusted.

Its main achievement in the solar system was sending back more data about Jupiter and Saturn. Due to the discovery of Titan's dense atmosphere, its masters on Earth temporarily ordered it to learn more about Titan, which delayed its schedule. Therefore, they decided to cancel its mission to continue exploring Uranus and Neptune and let its younger sister take over.

Due to its high speed, Voyager 1 soon surpassed Pioneer 10 and Pioneer 11, which were launched in 1972 and 1973 respectively, to become the longest-flying spacecraft. A lot has been said about the story of Voyager 1, so I won't go into details here.

The younger sister's way of travel was to stop and go along the way, making full use of the path of the four planets in conjunction. It not only explored Jupiter and Saturn successively, but also "inspected" Uranus and Neptune, the two coldest and most marginal planets. It is the earliest human probe to reach the dark and cold place to visit Earth's distant "brothers".

While following in the footsteps of her elder sister to explore the planets Jupiter and Saturn, scientists purposefully asked her younger sister to conduct more in-depth investigations based on some doubtful or unclear information discovered by Voyager 1, and discovered many new clues and phenomena, some of which surprised the scientists.

For example, it was discovered that the famous Great Red Spot storm in Jupiter's atmosphere is actually a complex storm system that reverses in a counterclockwise direction; it was also confirmed that there is active volcanic activity on Io, and the source of energy for these activities is most likely the tidal force between Jupiter and Europa and Ganymede; some strange features of several satellites such as Io, Europa, Ganymede, Callisto, and Callisto were also discovered, and new satellites such as Io XIV, XV, and XVI were discovered.

Voyager 2 arrived at Saturn in August 1981 after its older sister left Saturn in November 1980. It detected Saturn's atmosphere through radar and obtained data such as the temperature of Saturn's upper atmosphere was about -203 degrees Celsius, the lower atmosphere was about -130 degrees Celsius, and the North Pole was about -263 degrees Celsius.

After passing Saturn, the girl's shooting platform got stuck, which caused variables in the mission to Uranus and Neptune. Fortunately, the ground engineers discovered the problem in time. It was due to excessive "fatigue" that the lubricating oil was exhausted. After replenishing it, the mission was able to continue moving forward.

My sister's greatest achievement is visiting Uranus and Neptune

Uranus is about 2.9 billion kilometers away from the sun, and it takes 2.68 hours for light to reach there. However, Voyager 2 flew for more than eight and a half years and arrived at this cold planet on the edge of the solar system in January 1986. At its closest point, it was only 81,500 kilometers from the top of Uranus' atmosphere.

This was the first and only time that human beings approached this planet, and Voyager 2 made many new discoveries as soon as it arrived.

Uranus is the planet with the strangest motion in the solar system. Its rotation axis is tilted 97.77°, making it orbit almost lying down like a car tire. Voyager 2 detected the planet's unique atmospheric motion and magnetic field, discovered many unique and strange phenomena, analyzed the atmospheric structure and chemical composition, observed the nine known rings, discovered two new rings, and discovered 10 new satellites.

After leaving Uranus, Voyager 2 reached and approached Neptune in August 1989, with the closest distance to Neptune being only 4,827 kilometers, thus allowing humans to see the appearance of the most distant planet 4.5 billion kilometers away for the first time. The main achievements include: the discovery of 6 new satellites of Neptune, the first discovery of 5 rings of Neptune, the discovery of a huge black cloud belt at the south pole of Neptune and a storm zone as large as the Earth, etc.

Voyager 2 also conducted a detailed investigation close to Triton and discovered that it is the only satellite in the solar system that rotates in the retrograde direction of its main star. It is also the coldest celestial body in the solar system, with a surface temperature as low as -240 degrees Celsius. There are also three ice volcanoes that can spew methane or nitrogen ice particles up to 32 kilometers high.

The journey of Voyager 2 fulfilled the human dream of close-up exploration of all the planets, and sent back a large amount of data and pictures, which gave humans a deeper understanding of the coldest planet in the solar system. After that, Voyager 2 ended its exploration of the solar system and, like its sister, began to fly out of the solar system with all its heart.

Voyager 2 is flying out of the solar system in a different direction than its older sister. The older sister is flying towards the direction of Centaurus, heading towards the center of the Milky Way, while the younger sister is flying towards the direction of Canis Major, heading towards Sirius.

The fate of Voyager 2

Like its elder sister, Voyager 2 will spend its entire life floating alone in the dark and cold space. Since there is no atmospheric oxidation and resistance, it can theoretically float forever, and its ketone body will remain as new after 1 billion years. Like her elder sister, she carries a piece of high-purity uranium-238, a golden record, and a diamond phonograph needle.

Since the half-life of uranium-238 decaying into plutonium-239 is known to be 4.17 billion years, when Voyager 2 is lucky enough to encounter aliens, as long as these extraterrestrial civilizations have reached the level of human technology, they will be able to determine her departure time by analyzing the decay value of uranium-238. And from the information carried by the record, we can learn where she came from, who her owner is, and what Earth civilization is like.

The CD also includes greetings from Chinese people to aliens in Mandarin, Cantonese, Hokkien and Wu. One of the greetings is from a woman in Xiamen dialect: "Hello, space friends! Have you eaten? Please come and sit here when you are free"; there is also the music of "High Mountains and Flowing Water" played on the Chinese guqin; the photos on the CD include the majestic Badaling Great Wall and the warm scenes of ordinary Chinese families having reunion dinners.

However, it is hard to say whether humans will still exist and still be on Earth at that time. If humans really die out, perhaps Voyager 2 will become the only witness of human existence. Of course, this tombstone function is not unique to Voyager 2, but also to its older sister, Pioneer 10 and 11, and the New Horizons probe launched after them.

On December 10, 2018, Voyager 2 flew out of the heliopause and became the second human spacecraft to enter interstellar space. Since then, she has relied on NASA's Deep Space Exploration Station 43 in Australia to contact her family. In March 2020, Deep Space Exploration Station 43 was overhauled and upgraded. After this little sister who was far away from humans lost contact for 8 months, on October 30, 2020, Deep Space Exploration Station 43 completed the upgrade and re-issued instructions to Voyager 2. After a long wait of 34 hours and 48 minutes, she only received a reply of "Hello".

This simple reply is enough to prove that Voyager 2 is still in orbit, flying normally, and its gain antenna is accurately facing the Earth. As of 22:00 on May 29, 2022, Voyager 2 has flown 19.4 billion kilometers away from us. Like its older sister, most of its scientific instruments have been shut down. The nearly exhausted power can only maintain a few simple instruments to report detection data to the owner. (Picture below)

By 2025, she will run out of energy like her older sister and shut down all her instruments. By then, she will be like a kite with its string cut off, completely losing contact with humans. But she will continue to drift along the route set by humans by inertia, and in 28,000 years she will cross the Oort Cloud, the last boundary of the solar system. If she is not destroyed by the numerous icy celestial bodies there, she will completely fly out of the sun's gravitational control.

Afterwards, she will continue to fly towards the direction of Canis Major, and after 290,000 years, she will pass by Sirius 4.3 light years away, and fly to the deeper space until she is captured by aliens. We cannot know her final destination, but if one day she brings aliens to Earth, our descendants will still know what she has experienced over the years.

Now, we can only wish her a safe journey with the expectations and greetings of mankind. If you have any opinions on this, please feel free to discuss. Thank you for reading.

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