Why are the Voyager spacecraft getting closer to Earth?

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Why are the Voyager spacecraft getting closer to Earth?

For a few months each year, the distances between the Voyager spacecraft and Earth actually decrease. You might know that both Voyager spacecraft was launched into space in the 1970s and visited the outer planets through the 1980s. They’ve been heading out of our solar system ever since. In 2012, Voyager1 entered interstellar space. Then, in 2018, NASA announced that Voyager2 had entered interstellar space, too. They are both headed outward, never to return to Earth. So, can they get closer?

The answer is that for a few months each year, Earth in its orbit moves toward the spacecraft faster than they’re moving away. Earth’s motion around the sun is faster than the motion of the Voyager spacecraft. Earth moves through space at a speed of 67,000 miles per hour (30 km/s). Voyager 1 moves at a speed of 38,210 miles per hour (17 km/s). Voyager 2 moves at a speed of 35,000 miles per hour (15 km/s). So, for a portion of the year, Earth comes around the side of the sun and is speeding toward the spacecraft faster than they’re moving away. Therefore their distances to Earth are getting closer, if only temporarily. They never change their outward motion. It is we who change.

View larger. | Both Voyager spacecraft are rushing away from Earth and into interstellar space. Yet for a portion of every year, both spacecrafts’ distances to Earth decrease. How is this possible? This chart shows the location of Voyager 2 as it leaves the solar system. Image via TheSkyLive.com.

A closer look at Voyager 2 in relation to Earth

Let’s look specifically at Voyager 2 as an example. Every year from late February to the beginning of June, Voyager 2 actually gets closer to Earth. We measure the distance between objects in space in astronomical units, or AU. This measurement is based on the distance between Earth and the sun, which is one AU.

Distance from Earth to Voyager 2

    February 20, 2022 ~ 130.05518 AU
    February 22, 2022 ~ 130.05454 AU

Between these dates, Voyager 2 begins to get closer to Earth

    June 2, 2022 ~ 129.72179 AU
    June 4, 2022 ~ 129.72224 AU

Between these dates, Voyager 2 resumes getting farther from Earth

Chart with line going from lower left to upper right and slightly wavy.
View larger. | This graph shows the distance of Voyager 2 from Earth from January 2013, through December 2030. It’s not a straight line because as Earth circles the sun, its faster speed means that for a portion of every year, Voyager 2 and Earth temporarily get closer together. Image via TheSkyLive.com.

Did you know?

Every day, sister Voyager 1 travels 1,474,000 km farther from the Sun, & I travel 1,338,000 km. Earth travels ~2,573,000 km in that same day, so Earth is orbiting faster than we are leaving! That is why the distance to both of us is decreasing right now!

Bottom line:

The Voyager spacecraft are on a never-ending journey away from Earth. So, why do the distances between the spacecraft and Earth decrease for a few months every year? It’s because, for a few months, Earth moves toward the spacecraft faster in its orbit around the sun than the spacecraft moves away from us.

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