The spacecraft that has flown 23.54 billion kilometers, the last picture taken, makes mankind think deeply!

Exactly 45 years ago, Voyager 1 embarked on an epic interstellar voyage that took it as far as the deepest reaches of the solar system, to a space never before touched by humans. Voyager 1 is now 23.54 billion kilometers away, and it has long been the farthest spacecraft from Earth.

Nowadays, Voyager 1 is not lost in the universe, it still sends signals back to Earth from time to time. Among the data and photos that Voyager 1 has sent back, the most representative and most recorded in history is the last photo it sent back, which makes human beings think deeply, why would it say that?

The planets of the solar system

A long time ago, humans have long observed through the naked eye that five stars will pass between the stars, they are called planets, that is, water, gold, fire, Jupiter, and Saturn. Together with the Earth, where we live, humans have long known about the existence of the six planets.

After the birth of the astronomical telescope, astronomers discovered a new planet not visible to the naked eye, which is Uranus. After observing the orbital anomaly of Uranus, and the Newtonian theory of gravity, astronomers calculated the existence of the eighth planet, which was soon confirmed by observations, and people named the newly discovered planet Neptune.

Then later, astronomers discovered Pluto in the astronomical telescope. However, because Pluto is so small, it is no longer considered the ninth planet according to the new definition of a planet. Currently, there are only eight known planets in our solar system.

After entering the space age, humans finally had the opportunity to launch probes to explore these planets at close range, and Mars and Venus were visited one after another. But for human astronautics, the four most distant planets are still too far away to be detected.

A celestial "accident" that created the legendary Voyager mission

Astronomers have discovered that in the late 1970s and 1980s, Jupiter, Saturn, Uranus, and Neptune will appear in a rare geometric alignment, orbiting in a specific space on the same side of the Sun. If a probe is launched at that time, it will be able to use the gravitational pull of these planets to travel to the next planet through a gravitational slingshot effect.

In just one mission and without much fuel, the probe could travel all over the four giant planets. If you miss this rare opportunity, the next time you will have to wait until the distant 22nd century. And so, the Voyager mission was born.

In 1977, Voyager 2 was the first to launch, embarking on a legendary journey into space. Two weeks later, Voyager 1 followed suit and left Earth. Because of Voyager 1's faster initial velocity, it soon overtook Voyager 2 and reached the Jupiter system first.

We got our first close look at Jupiter's famous Great Red Spot, the superstorm that has been raging on Jupiter for centuries. With active volcanoes on Io, water on Io, and the largest moon in the solar system (5,300 km in diameter), these detections shook human perceptions at the time.

After finishing the exploration of the Jupiter system, Voyager 1 was accelerated by the gravitational force of Jupiter and flew towards the Saturn system. After reaching the Saturn system, Voyager 1 found that the structure of Saturn's halo is very complex with many layers.

More importantly, Voyager 1 took a close look at the mysterious Titan. Titan is arguably the most unusual moon in our solar system, covered by a thick atmosphere that may resemble the primitive Earth more than 4 billion years ago. If there is extraterrestrial life in our solar system, Titan is one of the biggest possibilities.

Because the flyby of Titan was an unplanned mission, it caused Voyager 1 to deviate from its intended trajectory, making it impossible to continue the planetary exploration mission that followed. Fortunately, there is still Voyager 2, which completed the exploration of Uranus and Neptune, the only close exploration of these two icy giants so far.

After the flight through the Saturn system, Voyager 1 deviated from the ecliptic plane, after which it was difficult to encounter large objects and its planetary exploration mission came to an end. At this point, Voyager 1's speed has already exceeded the escape velocity of the solar system, so it will fly forward to the depths of the universe.

The last look back

Thirteen years after leaving Earth, Voyager 1 came to a distance of 6 billion kilometers from Earth, at which point it had left the range of the eight planets. To save power for Voyager 1, some unnecessary equipment was turned off one by one. But before that, Voyager 1 looked back at the inner solar system and took one last picture, the famous "dull blue dot" below.

This is the home of Voyager 1, the place it left behind, and the only home for humans and millions of other species of life: Earth. From such a distance, the magnificent mountains and vast oceans are unrecognizable, and the entire planet has become a pixelated dot with a blue glow.

The deeper one gets into the universe, the more humbling it becomes, and this last photo returned by Voyager 1 is certainly the best proof of that. This photo is certainly thought-provoking; this little bright spot is all we have in the universe, and all people are born and live there.

The Earth is like tiny dust, suspended in the endless darkness of space, it looks so helpless and fragile, what reason do we have not to protect this only home? Without it, mankind is nothing.

Interstellar Messenger

Voyager 1's interstellar journey continues, and its next flight has no destination. In a vast universe, Voyager 1 will hardly meet another planet. In about 20,000 years, Voyager 1 will fly out of the solar system. It will be another 20,000 years before Voyager 1 makes a close flyby of an extrasolar star, but the closest distance is 1.6 light years, and it will not enter that star system.

Voyager 1's plutonium nuclear batteries are expected to continue to power the star until 2036, after which time it will be completely out of communication with Earth. Voyager 1 carries a gold-plated record of greetings in various human languages, basic human information, and the location of the solar system in the galaxy, with a view to alien civilizations discovering the human presence in the universe.

But considering that the universe is too empty, it is almost unlikely that Voyager 1, as an interstellar messenger, will be discovered by extraterrestrial civilizations. Wait until the distant future, the first to discover the lost Voyager 1 may be none other than humanity itself.