Cosmology: luminosity and magnitude

In summary, luminosity in cosmology is a measure of the energy emitted by a celestial object per unit time. It is different from magnitude, which is a measure of the apparent brightness of an object from Earth. Luminosity is calculated using the Stefan-Boltzmann law and is independent of distance. Absolute and apparent magnitude are also different, with absolute magnitude being a measure of an object's brightness at a standard distance. The luminosity of a star plays a key role in its classification based on spectral characteristics.
  • #1
Jozefina Gramatikova
64
9

Homework Statement


upload_2019-2-24_10-54-17.png


Homework Equations


upload_2019-2-24_10-54-53.png
[/B]

The Attempt at a Solution


(a)
52670785_2106751202949646_7243450039622696960_n.jpg?_nc_cat=100&_nc_ht=scontent.flhr4-2.jpg

53088147_2130416657004688_8045460836266803200_n.jpg?_nc_cat=108&_nc_ht=scontent.flhr4-1.jpg


(b)
53031585_380912926060200_2925124396479676416_n.jpg?_nc_cat=111&_nc_ht=scontent.flhr4-2.jpg


Could you tell me if what I am doing is correct? In part (b) they want M as a function of L so I assumed we have to get rid of the l. Do I have to use l(m=0) = 1.52 x 10 ^(-8) ?[/B]
 

Attachments

  • upload_2019-2-24_10-54-17.png
    upload_2019-2-24_10-54-17.png
    24.6 KB · Views: 601
  • upload_2019-2-24_10-54-53.png
    upload_2019-2-24_10-54-53.png
    31.4 KB · Views: 658
  • 52670785_2106751202949646_7243450039622696960_n.jpg?_nc_cat=100&_nc_ht=scontent.flhr4-2.jpg
    52670785_2106751202949646_7243450039622696960_n.jpg?_nc_cat=100&_nc_ht=scontent.flhr4-2.jpg
    37.2 KB · Views: 489
  • 53088147_2130416657004688_8045460836266803200_n.jpg?_nc_cat=108&_nc_ht=scontent.flhr4-1.jpg
    53088147_2130416657004688_8045460836266803200_n.jpg?_nc_cat=108&_nc_ht=scontent.flhr4-1.jpg
    32.7 KB · Views: 512
  • 53031585_380912926060200_2925124396479676416_n.jpg?_nc_cat=111&_nc_ht=scontent.flhr4-2.jpg
    53031585_380912926060200_2925124396479676416_n.jpg?_nc_cat=111&_nc_ht=scontent.flhr4-2.jpg
    32.2 KB · Views: 496
Physics news on Phys.org
  • #2
Yes, you need to use the given initial condition to solve for M as a function of L. You can use the initial condition to solve for the constant of integration in the solution.
 

FAQ: Cosmology: luminosity and magnitude

1. What is luminosity in cosmology?

Luminosity in cosmology refers to the total amount of energy emitted by an object in the form of electromagnetic radiation. It is a measure of the intrinsic brightness of an object, regardless of its distance from an observer.

2. How is luminosity different from magnitude?

Luminosity and magnitude are two different ways to measure the brightness of an object in space. Luminosity is an absolute measure, meaning it is independent of the observer's distance from the object, while magnitude is a relative measure that takes into account the object's distance from the observer.

3. What is the relationship between luminosity and magnitude?

The relationship between luminosity and magnitude is inverse. This means that as the luminosity of an object increases, its magnitude decreases. This is because an object appears dimmer the further it is from the observer, even if it has a high luminosity.

4. How is luminosity calculated?

Luminosity is calculated by measuring the total amount of energy emitted by an object in all wavelengths of light. This can be done by using a formula that takes into account the object's radius and temperature. Luminosity can also be measured directly through observations with telescopes and instruments.

5. Why is luminosity important in cosmology?

Luminosity is important in cosmology because it allows us to compare the brightness of objects at different distances. This helps us understand the true nature of objects in space, such as stars and galaxies, and their evolution over time. Luminosity is also used to calculate distances in the universe and to study the expansion of the universe.

Similar threads

Binary Stars and Apparent Magnitudes
Replies
1
Views
2K
The Mystery of Human Luminosity: A Comparison to Daily Energy Intake
Replies
2
Views
3K
Calculating the Feeding Rate of Supermassive Black Holes to Power Quasars
Replies
5
Views
1K
Using Eddington Luminosity to calculate mass
Replies
9
Views
4K
Luminosity of the Earth covered in bulbs
Replies
2
Views
1K
Body attached to a block by a spring, shaped like an inclined plane
Replies
1
Views
354
Homework - Interparticle distance between galaxies
Replies
2
Views
1K
Intensity of Stars and the Inverse Square Law Problem
Replies
10
Views
2K
Binary system of stars (##\alpha## - centauri)
Replies
5
Views
1K
Hertzsprung-Russell Diagram question
Replies
1
Views
868

Hot Threads

Recent Insights

Back
Top