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III. The Missing Mass Problem Measurements of the orbital speed of stars in the Milky Way and other galaxies give an estimated mass of the Milky Way and other galaxies, which are in contrast with mass estimates based on stars, star clusters, gas, and dust that are visible in these galaxies. The contrast between these kinds of measurements has led astronomers to infer that there must be a great amount of non-luminous matter in the outer portions of most galaxies. So in this section, we will repeat the calculation from sec II for a star which is 15 kpc from the center of the galaxy. 1. Assume that the orbital speed of a star is measured at a distance of 15 kpc from the center of our galaxy. If the rotational speed is 250 km/s, calculate the mass inside the orbit of such stars. 1000 pc = 206,265 AU a = r = 15 kpc = (15 kpc) * (AU/1 kpc) * (1 pc/2. Next calculate the period of the star's orbit around the center of the galaxy by calculating the distance the star travels in one period divided by the star's orbital velocity. But first, the circumference of the star's orbit is: d0 = 2 * Ï€ * r = 2 * (3.14) * AU 3. Calculate the Star's velocity in AU/yr: 1 AU = 1.49x10^8 km (250 km/s) * (AU/yr) 4. The Period of the Star's Orbit is: circumference_of_orbit / v_star 5. Calculate the combined mass of the Star and the portion of the Milky Way inside the Star's orbit: (M_star * (AU)^3) / (M_sun * yr)^2 6. How many billions of Sun Masses (M_Sun in the above formula) is this inside an orbit of 15 kpc?

Name: iii the missing mass problem measurements of the orbital speed of stars in the milky way and other galaxies give an estimated mass of the milky way and other galaxies which are in contrast w 05337
Uploaded: 2023-07-25T13:15:52-08:00
Duration: 33 s
Channel: Numerade
Description: iii the missing mass problem measurements of the orbital speed of stars in the milky way and other galaxies give an estimated mass of the milky way and other galaxies which are in contrast w 05337

          III. The Missing Mass Problem

Measurements of the orbital speed of stars in the Milky Way and other galaxies give an estimated mass of the Milky Way and other galaxies, which are in contrast with mass estimates based on stars, star clusters, gas, and dust that are visible in these galaxies. The contrast between these kinds of measurements has led astronomers to infer that there must be a great amount of non-luminous matter in the outer portions of most galaxies. So in this section, we will repeat the calculation from sec II for a star which is 15 kpc from the center of the galaxy.

1. Assume that the orbital speed of a star is measured at a distance of 15 kpc from the center of our galaxy. If the rotational speed is 250 km/s, calculate the mass inside the orbit of such stars.
1000 pc = 206,265 AU
a = r = 15 kpc = (15 kpc) * (AU/1 kpc) * (1 pc/2. Next calculate the period of the star's orbit around the center of the galaxy by calculating the distance the star travels in one period divided by the star's orbital velocity. But first, the circumference of the star's orbit is:
d0 = 2 * Ï€ * r = 2 * (3.14) * AU

3. Calculate the Star's velocity in AU/yr:
1 AU = 1.49x10^8 km
(250 km/s) * (AU/yr)

4. The Period of the Star's Orbit is:
circumference_of_orbit / v_star

5. Calculate the combined mass of the Star and the portion of the Milky Way inside the Star's orbit:
(M_star * (AU)^3) / (M_sun * yr)^2

6. How many billions of Sun Masses (M_Sun in the above formula) is this inside an orbit of 15 kpc?

iii the missing mass problem measurements of the orbital speed of stars in the milky way and other galaxies give an estimated mass of the milky way and other galaxies which are in contrast w 05337

Added by Katherine F.

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