Story by: Jack Meier
Voyager 1 has just made history by being the first manmade object to exit our solar system, NASA stated on Thursday. It has crossed the heliosphere, the magnetic boundary that defines the border between interstellar space and our solar system.
The probe and its brother, Voyager 2, were launched in 1977, sixteen days apart. Voyager 1 is currently at a distance of 18.8 billion kilometers from Earth, and its brother Voyager 2 is 15.3 billion kilometers away. Voyager 1 is currently traveling at a speed of 38,000 miles per hour.
Voyager 2 is estimated to leave the heliosphere in three to four years. Since Voyager 2’s plasma instrument is still functional, we will have a better idea of when exactly the probe crosses into interstellar space.
“In leaving the heliosphere and setting sail on the cosmic sea between the stars, Voyager has joined other historic journeys of exploration; the first circumnavigation of the globe, the first steps on the moon” Ed Stone, chief scientist on the Voyager mission remarked.
How they determined when the spacecraft actually crossed the threshold was tricky, as the plasma measuring instrument broke way back in 1980. To skirt around that handicap, the scientists working on the project measured the waves in the plasma around the craft, and used it to calculate density.
The vibrations were caused by a large coronal mass ejection (solar flare), from the sun in 2012. The ejection formed what Stone called a ‘solar wind tsunami.’
Between October 23rd and November 27th, the spacecraft traveled through an area with an electron density of 0.06 per cubic centimeter. This is still within the interstellar space range, meaning the craft passed through plasma with increasing electron density.
In the interstellar medium, the density of electrons is thought to be between 0.22 and 0.05 electrons per cubic centimeter. Interstellar plasma particles are created by the explosions of giant stars, scientists theorize.
The theory, led by the University of Iowa physicist Donald Gurnett, states that the concentration of plasma particles is thirty times greater outside the heliosphere than inside. This middle ground between the heliosphere and interstellar space is called the heliopause.
The probe itself has 68KB of data storage, much, much less than the average smartphone. Scientists communicate with it daily to retrieve the pictures and wipe the memory so more pictures can be taken.
“It’s the little spacecraft that could” said Suzanne Dodd, Voyager project manager.
Scientists are interested in observing the differences between our solar wind, and the solar wind from interstellar space. Our heliosphere is akin to a rock in a river, the solar wind has to flow around it like water around a rock.
Both probes carry the ‘golden record’, a 12 inch gold plated copper disk with sights and sounds from Earth. The idea was that if extraterrestrials find the probe, they will listen to the disk and learn about us and our culture.
The disk has 115 images, and many natural sounds such as birds, surf, thunder, wind, and animals. There is also a compilation of music from different genres and eras. There are greetings spoken in fifty-five different languages, beginning with Akkadian, an ancient Sumer language, and ending with Wu, a modern-day Chinese dialect.
Natural radioactive decay generates enough power to allow Voyager to communicate with Earth and run its instruments. The first instrument will be shut off in 2020, and the spacecraft will go dark in 2025.
But for now, the probe will forge on through the complete darkness that is interstellar space, and hopefully, one day, something else will pick it up.