# Finding the mass of our Galaxy and the amount of stars in our Galaxy

• seizureboi
In summary, the conversation discusses estimating the mass of the Milky Way Galaxy based on its rotation and the assumption that its mass is mainly concentrated in a central uniform sphere. Using the given information, the estimated mass of the Galaxy is 3.44425x10^41 kg and the estimated number of stars is 1.72213x10^11. The individual discussing the solution is unsure if their answer is correct and asks for help.
seizureboi

## Homework Statement

The sun rotates around the center of the Milky Way Galaxy at a distance of about 30,000 light-years from the center (1 light year=9.5x10^15 meters). If it takes about 200 million years to make one rotation, estimate the mass of our Galaxy. Assume that the mass distribution of our Galaxy is concentrated mostly in a central uniform sphere. If all the stars had about the mass of our sun (2x10^30 kg), how many stars would there be in our Galaxy?

## The Attempt at a Solution

For the mass of the Galaxy I got an answer of 3.44425x10^41 kg and I got 1.72213x10^11 stars. I'm pretty sure this isn't right. HELP!?

That looks about right to me. Why do you think it's wrong?

I would first like to commend you on your attempt to solve this problem. It is a complex and challenging task, and it is important to approach it with a critical and analytical mindset.

To begin, let's clarify some of the assumptions and calculations made in your attempt. The given distance of 30,000 light-years is not the radius of the Milky Way Galaxy, but rather the distance of our sun from the center. This means that the radius of the galaxy is actually much larger, and the mass distribution may not be as uniform as assumed.

Additionally, the time taken for one rotation is not a constant value, as the speed of rotation varies depending on the distance from the center. This means that the estimated mass of the galaxy may not be accurate.

To accurately determine the mass of the galaxy, we would need to take into account the distribution of mass, the varying speeds of rotation, and other factors such as dark matter.

As for the number of stars, assuming they all have the same mass as our sun may not be accurate. Stars come in a range of sizes and masses, and the average mass of stars in the galaxy may be different from that of our sun.

In conclusion, while your attempt is a good starting point, it is important to consider the limitations and uncertainties in the assumptions and calculations made. A more accurate and comprehensive approach would be needed to determine the mass and number of stars in our galaxy.

## 1. How do scientists determine the mass of our Galaxy?

Scientists use a variety of techniques, such as measuring the rotational speed of stars and gas clouds, to calculate the mass of our Galaxy. They also take into account the amount of dark matter, which cannot be directly observed but can be inferred through its gravitational effects.

## 2. What is the estimate of the mass of our Galaxy?

The current estimate of the mass of our Galaxy is approximately 1.5 trillion times the mass of our Sun. This includes the mass of stars, gas, dust, and dark matter.

## 3. How many stars are estimated to be in our Galaxy?

The estimated number of stars in our Galaxy is around 200-400 billion. However, this number could vary as new stars are constantly being formed and others may be destroyed.

## 4. How does the mass of our Galaxy compare to other galaxies in the universe?

Our Galaxy is considered to be a medium-sized galaxy, with a mass that is similar to other spiral galaxies. However, there are also much larger galaxies, known as elliptical galaxies, which can have masses up to 100 trillion times that of our Sun.

## 5. Can we directly observe the mass and number of stars in our Galaxy?

No, we cannot directly observe the mass and number of stars in our Galaxy. Instead, scientists use various indirect methods, such as measuring the motions of objects and studying the distribution of light, to make these estimates.

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