Star Density Should be a piece of cake

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SUMMARY

The discussion centers on calculating the density of stars in an introductory Astronomy course (Astr. 1020). The user seeks clarification on how to convert relative measurements of stars, such as Sirius, into absolute density values in grams per cubic centimeter (g/cm³). The correct approach involves multiplying the relative mass and radius of the star by the Sun's actual mass (1.989 x 1030 kg) and radius (6.957 x 1010 cm), respectively, and then applying the formula for density, which is mass divided by volume (volume of a sphere).

PREREQUISITES
  • Understanding of basic astronomy concepts, including stellar mass and radius.
  • Familiarity with the formula for the volume of a sphere.
  • Knowledge of SI units, specifically mass in kilograms and volume in cubic centimeters.
  • Basic mathematical skills for performing calculations involving cubic measurements.
NEXT STEPS
  • Learn how to calculate the volume of a sphere using the formula V = (4/3)πr³.
  • Research the actual mass and radius of the Sun for accurate conversions.
  • Study the concept of stellar density and its significance in astrophysics.
  • Explore how to convert between different units of measurement in scientific calculations.
USEFUL FOR

This discussion is beneficial for students in introductory astronomy courses, educators teaching astronomy concepts, and anyone interested in understanding stellar properties and density calculations.

gothicpie
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I am in Astr. 1020, and in my introductory Astronomy class I had last semester, we didnt learn anything. It was a "here's the study guide (aka the answers to the test)" kind of class so I didnt really learn that much.

Now, my Astr. 1020 teacher is rather difficult due to what I didnt learn last semester...

So on to the problem. For homework we have to find the density of Stars. It should be hard, mass (g) divided by volume (of a sphere, cm^3), I understand that much.

In the problems, we are given everything relative to the sun (I hope I'm stating that correctly). So, the data we have for the sun is 1.0m(sun) and 1.0R(sun). How am I supposed to do this and get g/cm^3?

I'm thinking, for example, Sirius (which is 2.0m(sun) and 2.0R(sun)) and multiply that by the mass and the radius of the sun, respectively. Is that right?

Thanks for the help, guys! :blushing:
 
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You are correct. If you want them in normal SI units then all you have to do is multiply their relative values by the suns actual values in SI units.
 
You must factor the cubic volume and mass to derive the correct density.
 

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