September 5 – Today In Science History – Voyager 1

Voyager Spacecraft Credit: NASA

September 5, 1977, was the day NASA launched the second of the Voyager series, Voyager 1.

Although Voyager 2 was launched two weeks earlier, Voyager 1 would be the first to its destination. The plan behind the Voyager mission was to take advantage of the alignment of the outer planets of the Solar System. This alignment, which happens every 176 years, would allow a spacecraft to visit one planet and then take advantage of its gravity to slingshot to the next. Voyager 1 would visit Jupiter and Saturn while Voyager 2 would visit Jupiter, Saturn, Uranus, and Neptune.

Voyager's Golden Record
Voyager’s Golden Record. Click for Larger Credit: NASA/JPL

Both probes contain a golden disk containing images of Earth, a map and a medley of songs and sounds of Earth in case some other civilization stumbles on the spacecraft through its travels. The compilation was selected by a committee headed by Carl Sagan of Cornell University. Sounds included the wind, surf, various birds and wildlife, thunder and greetings in 55 different languages. These disks are made of copper and gold plated. They are stored in an aluminum jacket with a needle and cartridge with instructions explaining how to play the record.

Voyager 1 arrived at Jupiter in March of 1979. It sent back its first pictures of Jupiter the previous April as it neared the planet. Once there, it discovered a thin ring around the planet and two new moons: Thebe and Metis. It also sent back impressive images of the moons Io, Europa, Ganymede, Callisto, and Amalthea. It also discovered active volcanos on Io’s surface.

Voyager would begin sending images of Saturn in 1980. Once it got there it made several new discoveries as well. It would spot three new moons: Prometheus, Pandora and Atlas and a new ring, now called the G ring. Another discovery involved the moon, Titan. Images showed the moon to be encompassed by an orange haze. No one could explain this haze and an explanation would come in January 2005 when the European Space Agency’s Huygens probe would land on the surface of Titan. The atmosphere was found to be full of nitrogen and hydrocarbons such as methane and ethane…basically, smog.

Once Voyager 1 left Saturn, its mission changed. It was heading out of our Solar System and its new task would be to report back what it finds as it passes through the heliopause. The heliopause is the boundary between the Sun’s solar wind’s influence and the interstellar medium begins. It is the effective boundary of our Solar System. Voyager crossed this boundary in August 2014. Its distance from the Earth at the time was 121 AU or 18 billion kilometers.

You can track the distance to Voyager 1 and 2 on NASA’s Voyager website. The odometer is fun to watch when you realize the speed Voyager is zipping along. Voyager 1 is currently the furthest man-made object in history. It has enough power to continue sending data back to Earth until 2025.

Voyager 1 gave NASA a slight scare at launch when it came within 4 seconds of running out of fuel. Fortunately, the spacecraft began its journey before running out of fuel.

Gold disk trivia: One of the songs included on the disk is Chuck Berry’s “Johnny B. Goode”. I guess even aliens will enjoy the tale of the country boy who could play his guitar, just like ringing a bell.

Notable Science Events for September 5

2017 – Nicolaas Bloembergen died.

Nicolaas Bloembergen
Nicolaas Bloembergen (1920 – 2017)
Dutch National Archives

Bloembergen was a Dutch-American physicist who shares half the 1981 Nobel Prize in Physics with Arthur Schawlow for the development of laser spectroscopy. Kai Siegbahn’s research into the development of electron spectroscopy earned him the other half of the prize.

Bloembergen also greatly improved the design of masers or microwave lasers and made several contributions to microwave spectroscopy. 

1977 – Voyager 1 was launched.

1948 – Richard C. Tolman died.

Tolman was an American physicist who demonstrated the charge carrying capacity in electricity is electrons moving through a conductor. He authored the standard statistical mechanics book in use for much of the mid 20th Century.

During the Manhattan Project, he served as scientific adviser to the military head of the program, General Groves.

1906 – Ludwig Eduard Boltzmann died.

Ludwig Boltzmann (1844-1906)
Ludwig Boltzmann (1844-1906)

Boltzmann was an Austrian physicist best known for his work in statistical mechanics and thermodynamics and his kinetic theory of particles in a gas. His statistical methods helped bridge the gap between the thermodynamics of a large system and the microscopic molecular level. He is also known for the law relating the energy given off by a black body object as a function of its temperature.