If the sun's mass is about average, how many stars are there in the Milky Way galaxy?
(This is all the information given in the question and I don't know where to go from here).
The mass of the Sun is of the order of 1030
But what do I do from there to get to the number of stars?
unless you have some idea of the mass of the galaxy, you are stuck.
Once you have that, just divide by the sun's mass to see how many "suns" there are in the galaxy.
To estimate the number of stars in the Milky Way galaxy, we can make use of some basic assumptions and calculations based on scientific data.
First, let's consider that our Sun has an average mass relative to other stars in the Milky Way. The mass of the Sun is roughly 1.989 × 10^30 kilograms.
Now, to estimate the number of stars in the Milky Way, we need to know the total mass of the galaxy. The mass of the Milky Way is approximately 1.5 × 10^42 kilograms.
Next, we can assume that the ratio of the Sun's mass to the total mass of the galaxy will be proportional to the ratio of the number of stars similar to the Sun to the total number of stars in the galaxy.
Mathematically, we can express this relationship as:
(Number of Sun-like stars) / (Total number of stars) = (Mass of the Sun) / (Mass of the Milky Way)
Plugging in the values we have, we get:
(Number of Sun-like stars) / (Total number of stars) = (1.989 × 10^30 kg) / (1.5 × 10^42 kg)
Simplifying the right side, we get:
(Number of Sun-like stars) / (Total number of stars) = 1.326 × 10^(-12)
Now, let's solve for the total number of stars in the Milky Way:
Total number of stars = (Number of Sun-like stars) / (1.326 × 10^(-12))
Since we don't know the exact number of Sun-like stars, we cannot give a precise value. However, estimates suggest that there are roughly 100 billion to 400 billion stars in the Milky Way galaxy.
Therefore, based on the given assumption that the Sun's mass is about average, we can estimate that there are between 100 billion to 400 billion stars in the Milky Way galaxy.
You get the mass of the galaxy this way:
It takes about 200 million years for one rotation around the middle of the galaxy, with the Sun about 30,000 light years (convert that to meters). Next, assume nearly all the galaxy mass is in an approximate spherical distribution about the center. Now you have a rotating model, with a period, and a radius... and you have from Newton,
mass= (4pi^2*r^3)/(G&T^2)
gravitational force=centripetal force
GM*Ms/r^2 =Ms(2PI*r /T)^2 /r
leading to
mass= (4pi^2*r^3)/(G*T^2)
a. convert the period to seconds.
b. use radius in meters (from light years)
c. calculate.
Then divide by the Mass of an average star, the sun, and you get the number of stars. It ought to come out pretty close to 175 billion.