If you have ever had a medical checkup, you have probably heard about the Body Mass Index (BMI) that it supposed to have an optimal value around 25. Probably you were told to take your weight in pounds, divide it by the square of your height in inches and multiply the result by 703 to find your BMI.
Well, astronomers think there are large number of stars and guess (estimate) that there are around 1 septillion stars in the Universe1. If you look at the night sky, you can see around 3,000 stars with the naked eye. A galaxy is a group of hundreds of billions of stars that are relatively close to each other.
Galaxies are the biggest groups of stars and can contain anywhere from a few million stars to many billions of stars. Every star that is visible in the night sky is part of the Milky Way Galaxy. To the naked eye the closest major galaxy â the Andromeda Galaxy, shown in Figure below â looks like only a dim, fuzzy spot.alaxies are the biggest groups of stars and can contain anywhere from a few million stars to many billions of stars. Every star that is visible in the night sky is part of the Milky Way Galaxy. To the naked eye the closest major galaxy â the Andromeda Galaxy, shown in Figure below â looks like only a dim, fuzzy spot.