Exploring the Cosmic Vacuum: How Much Space is Between Stars in the Observable Universe?

Imagine the vast expanse of space in our observable universe, where countless stars twinkle and stars form beautiful constellations. But between these celestial bodies lies something that might surprise you—just how much space is truly out there?

1. The Scale of the Observable Universe

The observable universe, defined as the part of the universe that can be observed from Earth, spans an astounding diameter of about 93 billion light-years. This unimaginably vast space is home to an estimated 10^22 stars, representing a stellar population that is mind-boggling in its density.

2. The Volume of a One-Light-Year-Sized Sphere

To delve into the concept of space between stars, let’s consider a one-light-year (LY) diameter sphere. The volume of such a sphere can be calculated using the formula:

Volume (4/3) π r3

Given a diameter of 1 LY, the radius (r) is 0.5 LY. Therefore, the volume of this sphere would be:

Volume (4/3) π (0.5 LY)3 ≈ 0.524 π LY3 or approximately 1.64 cubic light-years.

However, it’s more practical to use metric system for better understanding:

Volume π/6 cubic light-years or 4.4 × 10^57 m3.

3. Star Density and Star Volume

Let’s consider the size of an average star. On average, stars have a radius of about 500,000 kilometers (km), which translates to a volume of:

Volume (4/3) π (500,000 km)3 ≈ 5.24 × 10^18 m3.

Converting this to the volume of a one-light-year-sized sphere:

Volume 5.24 × 10^18 m3.

Now, let’s see how many such stars can fit into a one-light-year-sized sphere:

Stars per sphere Volume of sphere / Volume of a star

Stars per sphere ≈ (4.4 × 10^57 m3) / (5.24 × 10^18 m3) ≈ 8.4 × 10^38 stars.

This calculation reveals that if we attempt to fit stars from the observable universe into a one-light-year-sized sphere:

4. The Reality of Stacking Stars

Estimates indicate that the observable universe contains about 10^22 stars. This vast number far exceeds the capacity of a one-light-year-sized sphere. Even if we were to compress stars to the smallest possible size, the space between them would still be enormous.

5. Space Between Stars in Reality

The actual space between stars in the observable universe is incredibly vast, far greater than the number of stars could fill. For example, the distance between the nearest star systems to our own, Proxima Centauri, is several light-years. The average distance between stars in our Milky Way galaxy is around 4 trillion miles (6.5 trillion kilometers), or about 40,000 to 400,000 astronomical units (AU).

Given the vast differences in scale, the idea of fitting all observable stars into a one-light-year sphere or having significant space between each star is purely theoretical. It underscores the enormity of the universe and the vastness that exists beyond the confines of star systems.

Conclusion

While the concept of fitting stars into a one-light-year-sized sphere is an intriguing thought experiment, it serves more to highlight the vastness of space in the observable universe. The actual space between stars is immense, far beyond any realistic comparison. This exploration not only reveals the grandeur of the universe but also the importance of our efforts to understand its complexities.