Reaching the Limit: Solar System Boundary Quiz

The Heliopause is the correct answer. This is the magnetic "border" of our solar system. At this point, the constant stream of charged particles from the Sun (solar wind) is no longer strong enough to push back the gases and pressure from the rest of the galaxy.

False. The Oort Cloud is located far beyond the Heliopause. While the Heliopause marks the limit of the Sun's magnetic and particle influence, the Oort Cloud exists in the region where only the Sun's gravity remains dominant.

Heliosphere is the correct answer. Think of the Heliosphere as a giant bubble blown by the Sun. Everything inside this bubble is protected from the harshest cosmic rays of interstellar space by the Sun's magnetic field.

Voyager 1 and Voyager 2 are the correct answers. Voyager 1 crossed in 2012 and Voyager 2 in 2018. While New Horizons is heading that way, it has not yet reached the boundary, and Apollo 11 only went as far as the Moon.

They increase significantly is the correct answer. The Heliosphere acts as a shield. Once a spacecraft leaves this "bubble" and enters interstellar space, it is exposed to the full force of high-energy particles from other stars and supernovae.

True. The very edge of the Oort Cloud is defined by the "Hill Sphere," the point where the Sun's gravitational pull becomes weaker than the pull of the surrounding Milky Way galaxy and neighboring stars.

Subsonic is the correct answer. Before hitting the final Heliopause boundary, the solar wind hits the Termination Shock, where it abruptly slows down and becomes denser and hotter as it begins to interact with the interstellar medium.

Much closer is the correct answer. The Heliopause is roughly 120 AU from the Sun. The Oort Cloud doesn't even begin until about 2,000 AU and extends to 100,000 AU. The magnetic boundary is just a tiny fraction of the total distance to the gravitational boundary.

The Heliopause and the Oort Cloud are the correct answers. These represent the two different ways we define the "end" of the solar system: the end of the Sun's wind/magnetism and the end of the Sun's gravity.

The gas and dust between star systems is the correct answer. Once a spacecraft crosses the Heliopause, it is no longer traveling through the "Sun's neighborhood" but is officially moving through the matter that fills the gaps between the stars in our galaxy.

True. This marks the true physical limit of our solar system. Beyond this point, the Sun can no longer hold onto objects, and they would drift into the gravitational territory of other stars.

Interstellar is the correct answer. Just like a boat creates a wake or wave in the water as it moves, our whole solar system creates a "Bow Shock" as it moves through the gases of the Milky Way galaxy.

It would push further out is the correct answer. The position of the Heliopause is a balance of pressure. If the Sun's "breath" (solar wind) is stronger, it can blow a larger bubble into the interstellar medium, moving the boundary further away.

Forces end at different places, invisibility, and boundary movement are the correct answers. Because there is no "wall," scientists must choose between using the magnetic edge (Heliopause) or the gravitational edge (Oort Cloud) to define the end.

True. Everything beyond the outer shell of the Oort Cloud is considered part of interstellar space, where the Sun's influence is finally outweighed by the rest of the galaxy.

Heliosheath is the correct answer. This is the "waiting room" at the edge of the solar system where the solar wind is turbulent and compressed before finally reaching the edge of the Sun's magnetic domain.

About 1.5 to 2 years is the correct answer. This illustrates the massive scale of the Oort Cloud. While it takes light only 8 minutes to reach Earth, the gravitational edge of our system is nearly 2 light-years away.

Drop in solar wind, increase in cosmic rays, and magnetic field changes are the correct answers. These three physical changes told NASA scientists that the probes had officially left the Sun's protective bubble and entered the "void" between stars.

The zone of a star's gravitational dominance is the correct answer. Every object with mass has a Hill Sphere. For the Sun, the Hill Sphere's outer limit is where the Oort Cloud ends, marking the absolute maximum reach of its orbital control.

False. While it is much emptier than the space inside our solar system, interstellar space contains hydrogen and helium gas, dust, and high-energy particles (cosmic rays) left over from other stars.