It is a fact. Voyager 2 has entered interstellar space. The spacecraft exited the huge bubble of particles that surrounds the solar system on November 5, becoming the second man-made spacecraft to cross the heliosphere, the boundary between the Sun and the stars. The first was Voyager 1.
Coming second is no less fabulous achievement than coming first. Voyager 1 became the first spacecraft to exit the solar system in 2012, but the spacecraft’s plasma instrument stopped working in 1980, leaving scientists without a direct view of the solar wind. Voyager 2’s plasma sensors are still working, providing unprecedented views of the space between the stars.
“We have been waiting with great anticipation the last few months to see this,” said NASA solar physicist Nicola Fox at a press conference on December 10 at the American Geophysical Union meeting in Washington. DC (USA).
A great trip
NASA launched the twin Voyager spacecraft in 1977 on a grand tour of the planets of the solar system. After the initial tour ended, both ships continued traveling through the bubble of plasma originating from the sun.
“When the Voyager mission was launched, we didn’t know how big the bubble was, how long it would take to reach its limit, and if the spacecraft could last long enough to get there,” said Voyager project scientist Edward Stone.
For most of Voyager 2’s journey, the spacecraft’s Plasma Science Experiment measured the speed, density, temperature, pressure, and other properties of the solar wind. But on November 5, there was a sharp drop in the speed and amount of solar wind particles hitting the detector every second. At the same time, another detector began to pick up more high-energy particles called cosmic rays that originate from other parts of the galaxy.
Those measurements suggest that Voyager 2 has reached the region where the solar wind collides with the coldest and densest population of particles that fill the space between stars. Voyager 2 is now just over 18 billion kilometers from the sun.
Interestingly, Voyager 2’s measurements of cosmic rays and magnetic fields, which Voyager 1 could still make when it crossed the boundary, did not exactly match observations from the first space probe.
“That’s what makes it interesting,” Stone said. The variations are likely due to the fact that the two spacecraft exited the heliosphere at different locations, and that the Sun is in a different part of its 11-year activity cycle than it was in 2012. “We would have surprised if they had both ‘looked’ the same. “
Voyagers probably have between 5 and 10 years to continue exploring interstellar space, according to Voyager project manager Suzanne Dodd of NASA’s Jet Propulsion Laboratory in Pasadena, California.
“Both spacecraft are very healthy if you think of them as seniors,” Dodd said. The biggest concern is the amount of energy they have left and how cold they get. Voyager 2 is currently at about 3.6 ° C, close to the freezing point of its hydrazine fuel. In the near future, the team will have to shut down some of the spacecraft’s instruments to keep the spacecraft operational and send data back to Earth.
“We have tough decisions ahead of us,” Dodd said.
Experts expect the spacecraft to last until 2027. “That would be great,” concludes Dodd.
Referencia: NASA’s Goddard Space Flight Center / Voyager 2: Update from the edge of the solar system. American Geophysical Union meeting, Washington, D.C., December 10, 2018.
J. D. Richardson. Voyager 2 in the heliosheath. American Geophysical Union meeting, Washington, D.C., December 10, 2018.
