This Is How Our Place In The Galaxy Has Dramatically Changed Since 2009

The Solar System is embedded in a vast magnetized region created by the Sun called the heliosphere, but it looks less like a sphere and more like the tail of a comet. The shape of the heliosphere is not fixed. Instead, its boundaries shift as the flow of particles from the Sun change over a solar cycle.

Researchers have now published the first observations of the heliosphere across a full cycle, which lasts 11 years. The data, published in The Astrophysical Journal Supplements, was collected by NASA’s Interstellar Boundary Explorer (IBEX). The mission was supposed to last for two years but it has been extended to provide insight into how the heliosphere changes.

In particular, the team found that from 2009 to 2014 (when the cycle peaked), the heliosphere contracted when the flow of solar wind was slow and steady. As 2014 progressed, the solar wind increased by about 50 percent for a few years, leading to the expansion of the heliosphere.

The work revealed the heliosphere's many asymmetries. The boundary is much closer to the direction of the motion of the Solar System, like the wake of a boat. It is also much closer to the south pole of the Sun than the north pole. The tail of the heliosphere appears to be much further out than expected as well. 

The mission has “been hugely successful, lasting much longer than anybody anticipated. We’re lucky now to have a whole solar cycle of observations," David McComas, the principal investigator for the mission at Princeton University in New Jersey, said in a statement.

IBEX has also discovered an anomaly of interstellar particles at the boundary. This has become known as the IBEX ribbon, a long-standing mystery in interstellar physics. The data from the mission paints a vague picture but more data is needed. Luckily, IBEX will have a colleague soon with the Interstellar Mapping and Acceleration Probe (IMAP), which will be launched in late 2024.

“IMAP presents a perfect opportunity to study, with great resolution and sensitivity, what IBEX has begun to show us, so that we will really get a detailed understanding of the physics out there,” McComas said.