Skip to main content

How many galaxies are there in the universe?

First, we do not know precisely how many galaxies there are in the universe. There are several reasons why a precise count cannot exist with current technology and funding. Our way to determine the number of galaxies involves not just scanning of a specific region in the sky, but careful analysis to determine if what appears as a minuscule and faint dot of light is or is not a galaxy. That involves careful analysis of its spectrum of electromagnetic radiation, first to see if it has a typical spectrum of a single star or a galaxy, containing many stars, and second, to examine red shift to determine its distance and age. From several observations of specific patches of sky, astronomers extrapolate general figures. 


In many regions of the sky, small galaxies may be too faint to be seen or our views of them may be blocked by other objects. This means that astronomers need to make approximations based on what can be observed and intricate mathematical models which create estimates based on the observable number of galaxies in selected quadrants and estimates of the total mass of the universe based on other factors such as its speed of expansion. There is also a problem of definition of what constitutes a galaxy versus a proto-galaxy, quasar, or Seyfert galaxy. 


A rough current estimate is 200 billion galaxies, but that estimate is constantly being refined and revised. 

Comments

Post a Comment

Popular posts from this blog

Is there a word/phrase for "unperformant"?

As a software engineer, I need to sometimes describe a piece of code as something that lacks performance or was not written with performance in mind. Example: This kind of coding style leads to unmaintainable and unperformant code. Based on my Google searches, this isn't a real word. What is the correct way to describe this? EDIT My usage of "performance" here is in regard to speed and efficiency. For example, the better the performance of code the faster the application runs. My question and example target the negative definition, which is in reference to preventing inefficient coding practices. Answer This kind of coding style leads to unmaintainable and unperformant code. In my opinion, reads more easily as: This coding style leads to unmaintainable and poorly performing code. The key to well-written documentation and reports lies in ease of understanding. Adding poorly understood words such as performant decreases that ease. In addressing the use of such a poorly ...
Post a Comment
Read more

A man has a garden measuring 84 meters by 56 meters. He divides it into the minimum number of square plots. What is the length of the square plots?

We wish to divide this man's garden into the minimum number of square plots possible. A square has all four sides with the same length.Our garden is a rectangle, so the answer is clearly not 1 square plot. If we choose the wrong length for our squares, we may end up with missing holes or we may not be able to fit our squares inside the garden. So we have 84 meters in one direction and 56 meters in the other direction. When we start dividing the garden in square plots, we are "filling" those lengths in their respective directions. At each direction, there must be an integer number of squares (otherwise, we get holes or we leave the garden), so that all the square plots fill up the garden nicely. Thus, our job here is to find the greatest common divisor of 84 and 56. For this, we prime factor both of them: `56 = 2*2*2*7` `84 = 2*2*3*7` We can see that the prime factors and multiplicities in common are `2*2*7 = 28` . This is the desired length of the square plots. If you wi...
Post a Comment
Read more