When NASA launched Voyager 1 and 2 deep into space 40 years ago, each spacecraft brought along a golden record with sights and sounds from Earth, just in case any aliens were to stumble across it.

Nearly 4 decades ago after lifting off, NASA’s historic mission is still exploring the cosmos.

The twin spacecraft launched several weeks apart in 1977 — Voyager 2 on August 20 and Voyager 1 on September 5 — with an initial goal to explore the outer solar system.

Voyager 1 flew by Jupiter and Saturn, while its twin took advantage of an unusual planetary alignment to visit Jupiter, Saturn, Uranus and Neptune.

In 2013, Voyager 1 spacecraft made news when it succeeded in recording the sounds of extrasolar space coming from out of our home -the Solar System-.

The process was done using an onboard plasma wave instrument. This instrument detected the vibrations of dense interstellar plasma, or ionized gas, from October to November 2012 and April to May 2013.

The waves detected by the instrument antennae can be simply amplified and played through a speaker. These frequencies are within the decibel range heard by human ears.

Voyager 1 space probe is currently the farthest man-made object in space. The famous probe became the first human-made object to interact directly with interstellar space (the space out of the Solar System) when it passed through the “Heliopause”.

Yet, since the final boundary of our Solar System is bookmarked as where the Sun’s gravity is no longer dominant, thus the spacecraft will have to pass Oort Cloud the final frontline of our home in order to truly be in the interstellar space.

Oort Cloud is about one light year away from the Sun, roughly about halfway to the nearest star, Proxima Centauri. Travelling at speeds of over 56,315 km per hour, it will take the spaceprobe nearly 40,000 years to get out of the Solar System.

Can We Communicate With Voyager 1?

Though being launched 40 years ago it still receives commands from, and transmits information to Earth, currently pursuing its extended mission to locate and study the boundaries of the Solar System and outer Extrasolar surroundings.

Though it was launched 16 days earlier, Voyager 2 will never pass Voyager 1. Also the fastest man-made spacecraft “New Horizons” will never pass it too, despite being launched from Earth at a faster speed because Voyager 1 benefited from a number of gravity-assisted speed boosts.

Voyager 1 passed the region of “Termination Shock” as well as “Heliosheath” and the “Heliopause” regions, in which the later is known as the boundary of the Sun’s magnetic field (not to be confused with Sun’s gravity).

Voyager 1’s speed of 17 km/s helps it to escape from the Solar System gravity. Yet, its escape velocity in comparison to the Milky Way Galaxy’s (525 km/s) is quite tiny.

Thus, the promising probe will stay in the orbit of our Milky Way Galaxy and won’t exceed it to the larger “The Milky Way Subgroup of galaxies”.

The spacecraft Voyager 1 has long outlasted its originally planned lifespan. It gets its electrical power from three radioisotope thermoelectric generators (RTGs), which are expected to continue generating enough electric power to let the probe keep communicating with Earth at least until the year 2025.

Were it not for these dwindling consumables and the possibility of losing lock on the faint Sun, our tracking antennas could continue to “talk” with the Voyagers for another century or two.

Plasma consists of charged particles and is more prevalent in the extreme cold of interstellar space than in the hot bubble of solar wind that permeates the solar system.

Voyager 1, now 21 billion km from Earth, couldn’t make the measurement directly because its plasma detector stopped working more than 30 years ago.

The two Voyager probes contain gold phonographic records etched with music, greetings, sounds and images from Earth. The project was spearheaded by astronomer Carl Sagan, who died in 1996.

Flying by an average speed of 17k/s Voyager 1 and being at 99,900 AU (Astronomical Unit) away from the Solar System’s final border “Oort Cloud” Voyager 1 will exceed the solar gravity and exit the Solar System after 35,000 or 40,000 years from now.

NASA’s twin Pioneer spacecraft, launched in the 1970s, also are leaving the solar system, but they have run out of power to relay information back to Earth.