Our Voyager 1 spacecraft officially became the first human-made object to venture into interstellar space in 2012.
Whether and when our Voyager 1 spacecraft broke through to interstellar space, the space between stars, has been a thorny issue.
In 2012, claims surfaced every few months that Voyager 1 had “left our solar system.” Why had the Voyager team held off from saying the craft reached interstellar space until 2013?
Basically, the team needed more data on plasma, which is an ionozied gas that exists throughout space. (The glob of neon in a storefront sign is an example of plasma).
Plasma is the most important marker that distinguishes whether Voyager 1 is inside the solar bubble, known as the heliosphere. The heliosphere is defined by the constant stream of plasma that flows outward from our Sun – until it meets the boundary of interstellar space, which contains plasma from other sources.
Adding to the challenge: they didn’t know how they’d be able to detect it.
No one has been to interstellar space before, so it’s like traveling with guidebooks that are incomplete.
Additionally, Voyager 1’s plasma instrument, which measures the density, temperature and speed of plasma, stopped working in 1980, right after its last planetary flyby.
When Voyager 1 detected the pressure of interstellar space on our heliosphere in 2004, the science team didn’t have the instrument that would provide the most direct measurements of plasma.
Voyager 1 Trajectory
Instead, they focused on the direction of the magnetic field as a proxy for source of the plasma. Since solar plasma carries the magnetic field lines emanating from the Sun and interstellar plasma carries interstellar magnetic field lines, the directions of the solar and interstellar magnetic fields were expected to differ.
Voyager 2 Trajectory
In May 2012, the number of galactic cosmic rays made its first significant jump, while some of the inside particles made their first significant dip. The pace of change quickened dramatically on July 28, 2012. After five days, the intensities returned to what they had been. This was the first taste test of a new region, and at the time Voyager scientists thought the spacecraft might have briefly touched the edge of interstellar space.
By Aug. 25, when, as we now know, Voyager 1 entered this new region for good, all the lower-energy particles from inside zipped away. Some inside particles dropped by more than a factor of 1,000 compared to 2004. However, subsequent analysis of the magnetic field data revealed that even though the magnetic field strength jumped by 60% at the boundary, the direction changed less than 2 degrees. This suggested that Voyager 1 had not left the solar magnetic field and had only entered a new region, still inside our solar bubble, that had been depleted of inside particles.
Then, in April 2013, scientists got another piece of the puzzle by chance. For the first eight years of exploring the heliosheath, which is the outer layer of the heliosphere, Voyager’s plasma wave instrument had heard nothing. But the plasma wave science team had observed bursts of radio waves in 1983 and 1984 and again in 1992 and 1993. They determined these bursts were produced by the interstellar plasma when a large outburst of solar material would plow into it and cause it to oscillate.
It took about 400 days for such solar outbursts to reach interstellar space, leading to an estimated distance of 117 to 177 AU (117 to 177 times the distance from the Sun to the Earth) to the heliopause.
Then on April 9, 2013, it happened: Voyager 1’s plasma wave instrument picked up local plasma oscillations. Scientists think they probably stemmed from a burst of solar activity from a year before. The oscillations increased in pitch through May 22 and indicated that Voyager was moving into an increasingly dense region of plasma.
The above soundtrack reproduces the amplitude and frequency of the plasma waves as “heard” by Voyager 1. The waves detected by the instrument antennas can be simply amplified and played through a speaker. These frequencies are within the range heard by human ears.
When they extrapolated back, they deduced that Voyager had first encountered this dense interstellar plasma in Aug. 2012, consistent with the sharp boundaries in the charged particle and magnetic field data on Aug. 25.
In the end, there was general agreement that Voyager 1 was indeed outside in interstellar space, but that location comes with some disclaimers. They determined the spacecraft is in a mixed transitional region of interstellar space. We don’t know when it will reach interstellar space free from the influence of our solar bubble.
Voyager 1, which is working with a finite power supply, has enough electrical power to keep operating the fields and particles science instruments through at least 2020, which will make 43 years of continual operation.
Voyager 1 will continue sending engineering data for a few more years after the last science instrument is turned off, but after that it will be sailing on as a silent ambassador.
In about 40,000 years, it will be closer to the star AC +79 3888 than our own Sun.
And for the rest of time, Voyager 1 will continue orbiting around the heart of the Milky Way galaxy, with our Sun but a tiny point of light among many.
“Don Cornelius did not want to see how I really danced, I was doing Hip-Hop and it was foreign to people out in California. Don was like ‘oh no no no no no no no no, you’re a girl’. And I was like ‘what!?’”.
-Rosie Perez as a featured “Soul Train” Dancer (1983-1984)
This is a list I compiled based on movies I’ve either already watched or plan on watching in the near future. Please feel free to add any suggestions, recommendations, or requests for anything you’d like to see more of on this blog.
On this day in music history: June 25, 1984 - “Purple Rain”, the sixth album by Prince is released. Produced by Prince, it is recorded at First Avenue (w/ mobile recording truck) in Minneapolis, MN, The Warehouse in St. Louis Park, MN, The Record Plant in New York, NY, and Sunset Sound in Hollywood, CA from August 1983 - March 1984. Serving as the soundtrack to Prince’s motion picture debut, it is the first album officially credited to Prince & The Revolution. Recording of the music for the film begins on August 3, 1983 when the band perform a live benefit show at First Avenue in Minneapolis. The performance marks the debut of new guitarist Wendy Melvoin, with the master versions of “I Would Die 4 U” (#8 Pop, #11 R&B), “Baby I’m A Star” and the title track being recorded at this show. These performances appear on the finished album with only minimal post production. The film and albums rousing opener “Let’s Go Crazy” (#1 Pop and R&B) is recorded at Prince’s rehearsal space “The Warehouse”, after he asks recording engineer Susan Rogers to pull the equipment out of his home studio. The basic track is cut live in spite of having no isolation between the musicians, and electrical interference from various appliances in the building. The track “Take Me With U” (#25 Pop, #40 R&B), the artists duet with Apollonia Kotero is originally slated to appear on Apollonia 6’s album, but Prince changes his mind and includes it on “Purple Rain”. Original LP copies are packaged with a poster of the band (taken during the video shoot for “When Doves Cry”), with a limited number of US promo copies (some stock copies in foreign territories) pressed on purple vinyl. Released four weeks ahead of the film, the soundtrack is an instant critical and commercial smash, launching Prince into worldwide super stardom. It spins off five singles including “When Doves Cry” (#1 Pop and R&B), and the title track (#2 Pop and #4 R&B), becoming the sixth best selling soundtrack of all time. It also wins two Grammy Awards in 1985. “Purple Rain” is inducted into the Grammy Hall Of Fame in 2011, and in 2012 is added to the National Recording Registry by The Library Of Congress. On June 23, 2017, remastered editions of the album are reissued on CD, including a Deluxe Edition 3 CD + DVD set. The deluxe version includes the original album on disc one, with disc two featuring eleven bonus tracks of previously unreleased material. Disc three contains the 7" edits and 12" extended versions. The DVD features the “Prince & The Revolution Live!” concert video originally released in 1985. It is also issued with the new remaster on standard black vinyl, and as a picture disc. “Purple Rain” spends twenty four consecutive weeks at number one on the Billboard Top 200, nineteen consecutive weeks at number one on the R&B album chart, and is certified 13x Platinum in the US by the RIAA, earning a Diamond Certification.