How Big Is The Milky Way?

Almost everything we see when we gaze up at the stars on a clear night sky is part of the Milky Way Galaxy. If you reside somewhere with little to no light pollution, you will get a spectacular view of our galaxy's interior, allowing you to see innumerable stars. From our vantage point on Earth, it is very evident that the Milky Way is massive. In reality, the Milky Way is one of the most massive galaxies in its region. How vast is the Milky Way, and how is it calculated?

Calculating The Size Of The Milky Way

A computer-generated simulation of what the Milky Way looks like from the outside.

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It is not straightforward to calculate the size of our home galaxy. It is difficult to find distances in space. Astronomers used to determine distances in space using a technique called as parallax. The procedure is really straightforward, and you may even try it out for yourself. Stretch out your arm and place your thumb in front of your face. Then, with one eye closed, leave the other open. When you switch between open and closed eyes, you will notice that your thumb appears to change position.

To calculate how far your thumb is from your eyes, multiply the distance between your eyes by the angle of your thumb as it seems to change position. You can tell how far away your thumb is by knowing the distance between your eyes and the angle. Obviously, using a ruler or tape measurer would be lot easier, but things are not that simple in space.

Astronomers must first establish the diameter of Earth's orbit around the sun before applying this procedure in space. The Earth's orbit may be compared to the distance between our eyes. The apparent location of things in space appears to shift when the Earth rotates around the sun, similar to how our thumb appears to move when we close and open our eyes one at a time.

We can calculate the distance to faraway objects by knowing the diameter of Earth's orbit and the change in angle. Parallax is a pretty basic strategy that works well for objects that are close to us. The more away an item is, however, the less accurate parallax becomes.

Parallax works well up to 6,000 light years away, but it becomes less precise as you approach further out. Although more modern technology has enabled us to use parallax for distances of up to 30,000 light years, the margin of error in these figures is rather large. As a result, new approaches are required to establish bigger distances in space and the size of our galaxy.

Variable Stars

The most dependable approach for determining long distances in space is to use variable stars. Variable stars have their brightness alter over a short period of time. When we stare at a star, the light we perceive is referred to as apparent brightness, which refers to how brilliant the star appears to be. This is distinct from a star's absolute brightness, which is the actual brightness of the star. Distance and brightness have a direct relationship.

When an item is farther away, it seems darker than when it is closer. We can tell how far away an item is by knowing its absolute brightness. Unfortunately, estimating absolute brightness for most stars is difficult, if not impossible. However, one method of estimating a star's absolute brightness is to observe how its apparent brightness fluctuates.

Most stars do not vary brightness over a short time period, but variable stars do. Astronomers can tell how bright a variable star is by studying it and analyzing the difference in its apparent brightness. They can calculate the distance to the star by knowing its absolute brightness. Astronomers have been able to determine the real size of our galaxy using this approach. According to most estimations, the Milky Way is 100,000 to 200,000 light years broad.

How Big Is The Milky Way?