What exactly is the heliosphere? This is the final boundary between our system and interstellar space. Many people think that our solar system ends where Pluto is. However, our solar system is very huge. The most distant human creation in the universe is Voyager 1, and in more than 40 years it has not reached the end of the solar system. Much of the solar system is inhabited only by the solar wind and the various types of radiation that radiate from the sun. So it may seem that this area is completely empty.
What is the shape of the heliosphere?
For the first time, astronomers have been able to map the heliosphere in a 3D model. The heliosphere does not have the shape of a sphere, but the shape of a comet. The outer boundary of the heliosphere is called the heliopause, where the pressure of the solar wind is weak and interstellar space begins here. Researchers at the Los Alamos National Laboratory mapped the area in detail using data from the IBEX (Interstellar Boundary Explorer) satellite, which measures charged particles ejected from the far outside of the heliosphere.
“Physics models have theorized this boundary for years,” said Dan Reisenfeld, a scientist at Los Alamos National Laboratory and lead author on the study, which was published in the Astrophysical Journal. “But this is the first time we’ve actually been able to measure it and make a three-dimensional map of it.”
How was the model created?
The model was created using a similar technique to sonar. Astronomers have measured energetic neutral atoms (ENA) – particles formed during collisions between the solar and interstellar winds.
“The solar wind ‘signal’ sent out by the Sun varies in strength, forming a unique pattern,” explained Reisenfeld. “IBEX will see that same pattern in the returning ENA signal, two to six years later, depending on ENA energy and the direction IBEX is looking through the heliosphere. This time difference is how we found the distance to the ENA-source region in a particular direction.”
“In doing this, we are able to see the boundary of the heliosphere in the same way a bat uses sonar to ‘see’ the walls of a cave,” he added.
Earlier simulations were inaccurate because they were based on measurements of galactic cosmic rays (indirect ENA indicator). The newly published 3D map is the most accurate model yet. So far, however, we still don’t know much about the heliosphere. The heliosphere blocks 75% of galactic cosmic rays, which can catastrophically damage spaceships and the DNA of all astronauts. However, it is fascinating to find that it has a cometary shape and it will help scientists in their research.