The average distance between two solar systems can vary greatly, as it depends on the distribution and density of stars in a galaxy. In the Milky Way galaxy, for example, estimates suggest that the average distance between neighboring star systems is around 5 light-years. However, it's important to note that this is just an approximation, and distances can range from a few light-years to tens or hundreds of light-years.
Calculating the distance between two solar systems without exceeding the speed of light is a challenging task. Currently, our fastest spacecraft, such as Voyager 1, travel at speeds of about 17 kilometers per second (11 miles per second). At this rate, it would take tens of thousands of years to reach even the closest star system.
To estimate the distance between two solar systems, one could potentially use parallax measurements. Parallax is the apparent shift in the position of an object when viewed from different locations. By observing a star from two different points in Earth's orbit, astronomers can measure the parallax angle and use trigonometry to calculate the distance to the star.
However, parallax measurements are limited in their range. They are typically only accurate for relatively nearby stars, within a few hundred light-years. Beyond that distance, the angles become too small to measure accurately.
For distances beyond the range of parallax measurements, astronomers rely on other methods such as spectroscopic parallax, standard candles (using known luminosity of certain objects to estimate distance), or the cosmic distance ladder, which combines multiple distance measurement techniques. These methods are based on various properties of celestial objects and their observed characteristics.
It's worth noting that interstellar travel within a human lifetime is currently beyond our technological capabilities. The vast distances between solar systems present significant challenges, and faster-than-light travel remains purely speculative in the realm of science fiction.