Voyager 2, NASA’s spacecraft launched in 1977 on a mission to the outer planets, has discovered that our solar system is not round as it has been thought, but “dented” because of the local interstellar magnetic field of deep space, NASA scientists said Monday.

The spacecraft passed through what is already known as the termination shock in August and reached the barrier a billion miles closer to the sun than, Voyager 1, its twin, which reached that part of space in 2004. The termination shock is the region where charged particles from the sun suddenly slow down as they collide with other particles and a magnetic field in interstellar gas. The change of speed was visibly felt as it slowed down from 700,000 miles per hour to 350,000 miles per hour.

"Voyager 2 entered the termination shock almost 1 billion miles closer within the southern hemisphere of the heliosphere of the solar system than Voyager 1 previously had," said Voyager Project scientist Edward Stone of the California Institute of Technology.

Unlike its twin, Voyager 2 had a working instrument that was able to make the first direct measurements of the speed and temperature of the solar wind. Scientists believed that the temperatures within the termination shock would be about 1,000,000 degrees Fahrenheit (555,500 C) because the space particles slow down and are heated up when they encounter an obstacle in a normal shock wave. Surprisingly, the temperatures were much lower, around 200,000 degrees F.

What is more surprising is that Voyager 2 succeeded to make at least five crossing into the terminal shock within several days, unlike Voyager 1, which made only on crossing. This helped scientists to gather more data about our solar system, data that confirm a squashed shape for the magnetic bubble enveloping the solar system, which has been pushed inward in the southern hemisphere.

"So there's something outside pushing in on the southern hemisphere of the heliosphere," said scientist Ed Stone that is "otherwise distorting a more or less spherical surface."

The scientist believes this “dent” in the heliosphere is a proof of how strong the interstellar magnetic field is. The magnetic field is believed to be left over from the supernovae that exploded 10 million to 20 million years ago in a region of the Milky Way Galaxy known as the Scorpius-Centaurus Association.

It would take seven or ten years for Voyager 2 to reach the interstellar space, scientists believe. They also said that the Voyagers had enough radioactive fuel remaining to operate their transmitters until at least 2020 and send more information on Earth.

The new findings were released at the annual meeting of the American Geophysical Union in San Francisco.