How many stars are in the Milky Way galaxy?

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In summary, the question asks to estimate the number of stars in the Milky Way galaxy by assuming that each star has the same mass as our sun, is uniformly distributed in a sphere around the galactic center, and our star is on the edge of that sphere. To solve this, we need to find the mass of the object that our star is orbiting and then divide it by the mass of our star. To do this, we can use Gauss's law to find the mass enclosed by the sphere and then divide it by the mass of our star. Working out the calculations will be necessary to get an accurate estimate.
  • #1
mark96
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Pllllease help me I have been stuck on this for ages:

[HRW5 14-57E] A star, with mass 3.29 1030 kg, revolves about the center of the Milky Way galaxy, which is 3.33 1020 m away, once every 2.17 108 years. Assuming that each of the stars in the galaxy has a mass equal to that of our star, that the stars are distributed uniformly in a sphere about the galactic center, and that our star is essentially at the edge of that sphere, estimate roughly the number of stars in the galaxy.

Answer needed ASAP
(working out would also be nice)
Thanks
 
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  • #2
What have you tried so far?
 
  • #3
Here's what I think, find the volume of the star sphere. Then divide that by the mass of the star.
 
  • #4
Ive noticed a mistake in the question by the way. Where it says 3.29 1030kg, 3.33 1020m and 2.17 108 years it is supposed to say 3.39 x 10^30 kg, 3.33 x 10^20 m and 2.17 x 10^8.

Keep trying please

I think this may be a uni type of question.
 
  • #5
You need to find the mass of the object that the star is orbiting such that it orbits at that speed at that distance. you can then divide that by the mass of your star to find how many stars
 
  • #6
i think you would need Gauss's law. find out the acceleration of the star, then apply gauss's law to find out the mass enclosed by that sphere.
 

1. What makes a star difficult to study?

There are many factors that can make a star difficult to study, such as its distance from Earth, its size and brightness, and the presence of other objects in its vicinity.

2. How do scientists measure the distance to a difficult star?

Scientists use a variety of methods to measure the distance to a star, including parallax, spectroscopic parallax, and the cosmic distance ladder. These methods involve using tools such as telescopes, spectroscopes, and mathematical equations to calculate the distance based on the star's characteristics and observations.

3. Can difficult stars be studied with the naked eye?

Some stars, such as the ones in our own galaxy, can be seen with the naked eye. However, many difficult stars are too far away or too dim to be seen without the aid of telescopes and other instruments.

4. How do scientists determine the size and brightness of a difficult star?

Scientists use a combination of techniques, including photometry and spectroscopy, to determine the size and brightness of a difficult star. These methods involve measuring the amount of light emitted by the star and analyzing its spectral characteristics.

5. What can we learn from studying difficult stars?

Studying difficult stars can tell us a lot about the universe, such as its age, composition, and evolution. It can also help us understand the life cycle of stars and the formation of galaxies. Additionally, studying difficult stars can provide insights into the physical laws and processes that govern the universe.

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