The Voyager 1 and Voyager 2 space probes began their long journey in 1977. Beyond NASA’s expectations, the scouts are still working, but slowly several instruments are being shut down. This means that the devices will last for a few more years, after which contact with the earth is broken and they float silently through the endless space.
They should really only last five years after launch, but Voyager 1 and 2 just keep delivering new results. “We are now 44.5 years further,” Ralph McNutt recently told Scientific American† McNutt has worked at the Johns Hopkins University Applied Physics Laboratory for much of his career on Voyagers. “We’ve reached ten times the target life of those things.”
Voyager 1 is now about 22.5 billion kilometers from Earth. Voyager 2 at over 12 billion miles. No man-made devices have gone further into space than these probes. Voyager 2 took off first, on August 20, 1977, and Voyager 1 followed two weeks later. The probes are identical to each other.
The scouts were supposed to take measurements of the planets Jupiter, Saturn, Uranus and Neptune. In 1977 the planets were in exactly the right position so that they could all be visited. That happens once every 176 years.
New photos and information about neighboring planets
The missions were successful. Among other things, new close-up photos of the planets were taken. The probes also detected lightning on Jupiter for the first time, proving that it could also strike on other planets. In addition, measurements were taken of the planet’s atmosphere and geography. New images were made of Saturn’s rings around it.
Voyager 1 continued its journey into the solar system without seeing any other planets, but Voyager 2 passed by Uranus and discovered that the planet had not nine but at least eleven rings. Twelve years after launch, in 1989, Voyager 2 reached Neptune. After the probe photographed the planet, its cameras were turned off to conserve power for other instruments.
Voyager 1 took another 60 photos of the solar system in 1990. The explorer was then at a distance of 6.4 billion kilometers from Earth. The Earth was also visible in those photos, as a small dot. The photo has since become known as the ‘pale blue dot’ and there is still no photo taken at a greater distance.
The dot on the right is Earth. Source: EPA.
The dot on the right is Earth. Source: EPA. Photo: EPA
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Probes now float through interstellar space
Both probes are now far from our solar system. Voyager 1 left our solar system in August 2012, and Voyager 2 did the same in November 2018, more than 40 years after its launch. The scouts now float further and further through interstellar space; the endless space between the stars.
The scouts are still taking measurements. Voyager 1 made headlines last year when it launched a vague monotonous hum picked up. Scientists think the sound probably comes from small amounts of gas in the space between different galaxies.
By recording the hum, the scientists hope to be able to determine specific properties of the environment outside the solar system, such as the density of space. That could help astronomers better understand interstellar space. The information may also provide insight into the boundary between interstellar space and the boundary of the solar system, known as the heliopause.
Chuck Berry on board on a gold record
The probes require very little energy to operate. But for the past three years, NASA has been shutting down heating elements and other non-essential components to stretch the remaining energy supplies as long as possible. Voyager 1 and 2 are expected to lose communication with Earth sometime between 2025 and 2030.
They will then continue to float through the endless universe. Both probes carry a gold gramophone record with information about the Earth. It contains 115 pictures, greetings in 55 languages and earthly sounds, such as the sound of wind, rain and a human heartbeat. There is also an hour and a half of music, including by Beethoven, Bach and Chuck Berry.
Voyager 1 will reach its next star, Proxima Centauri, in about 16,700 years Scientific American† Voyager 2 passes there 3,600 years later.
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