To the astonishment of everyone, Voyager 1, after decades of venturing deep into space, has made contact with an extraterrestrial entity in interstellar space.
The Voyager mission started in 1977 when two space probes, Voyager 2 on August 20 and Voyager 1 on September 5, were launched. Even though it was launched later, Voyager 1 was moving at a higher speed and reached the destination first. Both missions were designed to study Jupiter and Saturn, offering detailed data on these gas giants, their moons, and other aspects of space.
Discoveries in Interstellar Space
Voyager 1 is the farthest man-made object and sends information from over 22.7 billion kilometers away from Earth. Voyager 1 sent information that found interstellar space to be filled with a steady presence of plasma, contrary to what was believed before.
One of the most significant observations is a consistent low-frequency rumble, which was measured at around three kilohertz. This observation verifies the presence of plasma, which is a state of matter wherein electrons have been removed from atoms because they were too hot.
The Existence of Plasma in Interstellar Space
Before this, Voyager 1 had seen disruptions in the plasma due to coronal ejections. Since the last three years, the spacecraft has documented a persistent detection of plasma at lower levels, indicating that this material is present in abundance even away from the Sun's effect.
Scientists have calculated that the plasma picked up by Voyager 1 stretches at least 1.5 billion kilometers, using the spacecraft's velocity of 61,000 kilometers per hour. But there are still questions that need to be answered:
Where does this plasma originate if it is not from the
Sun?
Why was it not picked up before if Voyager 1 had
already been in interstellar space for years?
Voyager 2 and Its Discoveries
In 2018, Voyager 2 joined the second spacecraft to
venture into interstellar space, six years behind Voyager 1. Its instruments
validated spectacular alterations in energetic particles:
A decrease in the number of heliospheric particles was
observed.
The presence of cosmic rays rose dramatically.
The second major finding was that the magnetic field of the heliopause (the region of transition from the heliosphere to interstellar space) is entirely parallel to the magnetic field of the heliosphere. Though Voyager 1 had already recorded this phenomenon, Voyager 2 replicated it, bringing new questions on its cause.
Plasma Temperature and Density Differences
One of the most unexpected Voyager 2 discoveries was the contrast between the temperature and density of the plasma in the two zones:
Within the heliosphere, the plasma is warmer than had
been expected and undergoes a rise in temperature before venturing into
interstellar space.
In interstellar space, plasma is colder and denser,
contrary to expectations based on scientific theory.
These contrasts are unexplained and a focus of study for astronomers.
Uranus and Neptune exploration
Voyager 2, apart from observing Jupiter and Saturn, was the lone spacecraft to reach Uranus and Neptune.
Uranus (1986): Ten new moons, some as-yet unknown
rings, and a distorted surface were found on the moon Miranda, which hinted
that it had split apart and reformed. Also, incredibly cold temperatures of as
much as -214°C were measured, the coldest planet in the solar system.
Neptune (1989): Voyager 2 found six new moons, four rings, and the Great Dark Spot, a huge storm due to powerful gusts of wind .
The Voyager Legacy
The Voyager probes have transformed our knowledge of the solar system and interstellar space. Both, despite their age, continue to yield useful data and are likely to keep running for a few more years, offering vital information regarding the secrets of the universe.
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