The view of a small section of the Milky Way from Canyonlands National Park in Utah, USA (Photo: National Park Service).
Similar to the diversity of life on Earth, galaxies in space come in various shapes and sizes, each with its unique characteristics.
Our planet resides within the Milky Way, a spiral galaxy where stars gather in spiral arms, circling the galactic center. Other galaxies take elliptical shapes or irregular forms, presenting a stunning array of diversity.
Before calculating the number of stars in the universe, astronomers first estimate the number of galaxies. To achieve this, they capture detailed images of small sections of the sky and count all the visible galaxies. This number is then multiplied by the necessary images to cover the entire sky.
The answer: There are approximately 2 trillion galaxies in the universe.
In reality, astronomers don’t know precisely how many stars exist within each of those 2 trillion galaxies. Most of these stars are incredibly distant, making it nearly impossible to calculate accurately.
However, we can make reasonably educated guesses about the number of stars in our own Milky Way. These stars exhibit a wide range of sizes and colors.
For instance, our Sun, located within the Milky Way, is a white star of average size, with a core temperature of about 15 million degrees Celsius. Larger, heavier, and hotter stars tend to appear bluish, like Vega in the Lyra constellation, while smaller, lighter, and cooler stars often have a reddish hue, like Proxima Centauri.
Stars of different colors emit varying amounts of light. By measuring a star’s light, including its color and brightness, astronomers can estimate how many stars our galaxy contains.
Using this method, scientists have determined that the Milky Way harbors approximately 100 billion stars.
Using the Milky Way as a model, we can multiply the number of stars in a typical galaxy (100 billion) by the number of galaxies in the universe (2 trillion).
This figure is truly mind-boggling and challenging to fathom, but it remains an estimate, a glimpse into the vast cosmic expanse.