Two machines fly far in space. 

{ "
In 1977, NASA launched two space probes. We call them Voyager 1 and Voyager 2. They were sent to visit the outer planets. 
These probes used a special way to move. They used gravity assists. This means they flew near big planets to gain speed. This helped them reach far places like Jupiter and Saturn.
Voyager 1 flew past Saturn and its moon, Titan. Then it moved away from the planets. Voyager 2 kept going. It visited Uranus and Neptune too. 
Now, both probes are in interstellar space. This is the area outside our solar system. Voyager 1 entered this space in 2012. Voyager 2 entered in 2018. They are the only human-made objects to reach this place. Voyager 1 is the farthest object from Earth. It is moving very fast. It travels at 17 kilometers every second. The probes use power from RTGs. These are tools that make power from heat. The power is getting low. Scientists must turn off tools one by one. We hope they work for many years.
The Voyager program is a famous American scientific mission. It uses two special space probes named Voyager 1 and Voyager 2. 

The probes move through space using a method called gravity assist. This means they fly close to a large planet to gain speed. The planet's gravity pulls on the probe and speeds it up. 
The idea for this mission started in the 1960s. An engineer named Gary Flandro thought of a "Grand Tour" in 1964. He noticed a rare alignment of the planets. This alignment happens only once every 175 years. It allowed a spacecraft to visit many planets using gravity. NASA's Jet Propulsion Laboratory began working on the idea in 1966. The mission was almost canceled in 1971 due to funding changes. Later, the mission was renamed from the Mariner series to Voyager.
Many specific facts tell the story of these travelers. Voyager 1 was launched after Voyager 2 in 1977. Voyager 1 entered interstellar space on August 25, 2012. Voyager 2 reached the interstellar medium on November 5, 2018. As of May 25, 2024, Voyager 1 is moving at 17 km/s. Voyager 2 moves at a speed of 15 km/s. Each probe carries many scientific tools. These tools include cameras and instruments to detect radiation. 
You can think of the Voyagers as our furthest messengers. They carry information back to us from the dark parts of space. They have passed the heliopause, which is the edge of the Sun's influence. This area is called interstellar space. It is the space between the stars. 
The Voyager program is a landmark American scientific mission. It utilizes two interstellar probes, Voyager 1 and Voyager 2, to explore the outer reaches of our solar system. 

To reach such distant worlds, the probes use a technique called gravity assist. This process involves maneuvering a spacecraft through the gravitational field of an intermediate planet. The planet's gravity pulls on the craft, which increases its velocity.
The two spacecraft were designed with specific components to function in deep space. Each probe features a high-gain antenna, or HGA, which is a large dish used to communicate with Earth. 
The origins of the mission date back to the 1960s. An aerospace engineer named Gary Flandro conceptualized the "Grand Tour" in 1964. He discovered a rare alignment of the outer planets that occurs only once every 175 years. This alignment made it possible to visit multiple planets using gravity assists. NASA's Jet Propulsion Laboratory endorsed the idea in 1966. However, the original Grand Tour mission was canceled in December 1971. Funding was redirected to the Space Shuttle program at that time. In 1972, a scaled-down version of the mission was proposed. This version used two identical spacecraft derived from the Mariner series.
Significant milestones mark the journey of these two explorers. Voyager 2 was launched first, followed by Voyager 1 later in 1977. Voyager 1 became the farthest human-made object from Earth during the 1990s. It surpassed the older Pioneer 10 and Pioneer 11 probes. In December 2004, Voyager 1 crossed the termination shock. This is the boundary where the solar wind slows to subsonic speeds. In 2012, Voyager 1 officially entered interstellar space.
Numerical data helps us understand the scale of this mission. As of May 25, 2024, Voyager 1 is moving at a velocity of 17 km/s relative to the Sun. Voyager 2 moves at a velocity of 15 km/s. The probes are incredibly far from Earth and the Sun. Scientists expect that by approximately 2025, there will no longer be enough power to operate any scientific instruments. This is due to the dwindling energy from the RTGs. Even as they lose power, the probes remain important records of our reach into the cosmos. They continue to drift through the dark, silent regions of interstellar space.
The Voyager mission connects our understanding of the solar system to the wider galaxy. By studying the heliopause, scientists learn about the boundary of the heliosphere. The heliosphere is the region dominated by the solar wind. 
🖼️ Images & Media (23)
+ 11 more
More to explore
✨ What else?
Related topics you might enjoy
🔬 Go deeper
More advanced topics to explore
🪜 Step back
Simpler topics to build understanding
What is Nepedia?
A free, ad-free encyclopedia for children. Every article is written at five reading levels, so the same page works for a five-year-old and a fifteen-year-old — use the level switcher above to see this one change. No account needed to read.