Last year NASA's Voyager 1 raised controversy when NASA asserted that the spacecraft had left our sun's bubble, and entered interstellar space. This would make it the first man-made object ever to enter interstellar space. Now, NASA reported on July 7 that Voyager has experienced a new "tsunami wave" from the sun. These waves are what led scientists to believe that Voyager had entered interstellar space in the first place. These new waves are extra evidence, confirming that the spacecraft has, in fact, entered interstellar space, as per NASA.

"Normally, interstellar space is like a quiet lake," said Ed Stone of the California Institute of Technology in Pasadena, Calif., the mission's project scientist since 1972. "But when our sun has a burst, it sends a shock wave outward that reaches Voyager about a year later. The wave causes the plasma surrounding the spacecraft to sing."

Interstellar space is a new frontier for space travel. However, this does not mean that the Voyager has left our solar system yet. The NASA statement defined interstellar space as "a region between the stars filled with a thin soup of charged particles, also known as plasma." If the Voyager continues along its path, it may leave the solar system. This is the farthest a man-made space probe has ever flown from Earth.

"All is not quiet around Voyager," said Don Gurnett, a researcher who was instrumental in determining that the Voyager had entered interstellar space. "We're excited to analyze these new data. So far, we can say that it confirms we are in interstellar space."

"Tsunami waves" from the sun are created from periods of increased activity from the sun, when the sun ejects material from its surface. These ejections are called coronal mass ejections, and they generate pressure, waves. The Voyager 1 has recorded three tsunami waves since 2012. The first was very small, and was only discovered after the fact when researchers went back and looked at the data, but the second wave was clearly registered in March 2013. The team has newly discovered readings from a third wave from the sun, which was first seen in March 2014.

Stone said the measurement system works because the tsunami waves ring the plasma in interstellar space "like a bell," and a plasma wave-reading instrument on the Voyager probe measures the frequency of the ringing, while another cosmic ray-reading instrument reveals the source of the ringing, which is the shock wave from the sun.

Voyager 1 was launched in 1977, along with a twin spacecraft, Voyager 2. Together, they are the longest continuously operated probes in space. Voyager 2 is expected to enter interstellar space in a few years.