Dark Matter, calculating missing mass

In summary, the Andromeda galaxy has a velocity of 250 km/s and an observed mass of 1 x 10^42 kg. Using the equations Fc=mv^2/r and Fg=Gm1m2/r^2, the invisible mass can be calculated by subtracting the visible mass from the total calculated mass. This will give a percentage of missing mass that can be used to understand the overall composition of the galaxy.
  • #1
cherioslover
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Homework Statement


The andromeda galaxy has a velocity of 250 km/s as it rotates. The observed mass is 1 x 10^42 kg. If the galaxy is roughly a circle with a diameter of 66,00 light years how much mass is not accounted for visibly?

Homework Equations



Fc=mv^2/r and Fg=Gm1m2/r^2


The Attempt at a Solution



There was no answer, i know I am supposed to calculate the the velocity and its mass, then but to get the percent of mass missing i think you divide the difference between the the calculated mass and given mass by the calculated mass or something like that. But i am still rather confused at what to do. I am not looking for someone to complete my homework, just to help me understand how to do this question.
 
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  • #2
But i am still rather confused at what to do.
Start with the part you described - calculate the mass with the formulas. It will be larger than 1042 kg, and this number is (visible mass)+(invisible mass). Can you calculate the invisible mass?
 

1. What is dark matter?

Dark matter is a hypothetical type of matter that makes up about 27% of the universe. It does not interact with light, which is why it cannot be seen directly.

2. How is the mass of dark matter calculated?

The mass of dark matter is calculated by observing the rotation of galaxies and clusters of galaxies. By measuring the speed at which objects are moving, scientists can determine the amount of mass needed to hold these objects together. This missing mass is attributed to dark matter.

3. What is the importance of calculating missing mass?

Calculating missing mass is important because it helps us understand the structure and evolution of the universe. It also provides evidence for the existence of dark matter and helps us study its properties.

4. How is dark matter different from regular matter?

Dark matter is different from regular matter in that it does not interact with light and other forms of electromagnetic radiation. It also does not interact with regular matter through the strong or weak nuclear forces, only through gravity.

5. Why is dark matter important in our understanding of the universe?

Dark matter is important in our understanding of the universe because it makes up a significant portion of the total matter in the universe. Without taking dark matter into account, our understanding of the formation and evolution of galaxies and the large-scale structure of the universe would be incomplete.

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