Apparent magnitude Definition and 26 Threads

Hello, When we talk about the luminosity, apparent magnitude or absolute magnitude of a star, are we talking about all wavelengths of EM radiation or just a certain range? I've read that luminosity is basically the power output of all types of radiation, but the apparent magnitude scale is...

Hello everyone! What would've been the apparent magnitude of the moon if it were 1000 times closer? Can we even talk about an apparent magnitude in the case of a large solid angle?

From what I understand, in the equation P=\sigma AT^4, P is the power output of the star which is the energy radiated per second in EM radiation of all frequencies, and I think luminosity is also defined as the energy radiated per second in EM radiation of all frequencies. Therefore luminosity...

Hey, Could anyone explain why Ia/Ib=2.512^(Mb-Ma), Where "Ia" and "Ib" are intensities of star a and star b and "Mb" and "Ma" are the apparent magnitudes of star A and star B? I thought the formula would be Ia/Ib=(2.512)^(Ma-Mb) because Ia=2.512^Ma and Ib=2.512^Mb. Thank You

Homework Statement A binary star system at a distance of 85pc consists of two stars of equal luminosity that are so close together that they are observed in a telescope as a single image. If the apparent magnitude of the two stars combined is 10.7 what would be the apparent magnitude of just...

Hi guys, I've seen a lot of textbooks converting between 2 apparent magnitudes to the ratio of 2 fluxes. But I just want to know how to convert 1 ( ONE, UNO , 1, NOT 2 ) flux to 1 ( ONE, UNO, 1, NOT 2 ) 1 Apparent Magnitude. I think I saw my professor wrote this down, but am not sure . Is this...

What does this statement mean: "Apparent magnitude of a star, X, is m." ? m_2 - m_1 = -2.5 log (B_2/B_1) Apparent magnitudes are defined relatively, right? We can talk about differences in apparent magnitudes. If i know the ratio of the brightnesses, i can find out the difference in...

Hello everyone, I've been wondering if I can calculate the apparent magnitude of The Moon since I know the apparent magnitude of The Sun(say -27mag) and reflection coefficient of Moon's surface(say 0.12). We know the equation \Delta m = -2.5 log_{10}(I/I_0) Where I is the flux of the...

Homework Statement The main sequence can be approximated by a relation of the form L\proptoT^5 . In Cluster A, a main sequence star called Star α has the same B – V colour as the Sun, and a V-band apparent magnitude of 11.3. The effective temperature of Star α is 5800K. In Cluster B, a main...

I know there there has to be a simple answer to this, but I can't understand where it's at. Here is the question. Find the apparent magnitude of the Moon [Earth's] as seen from Mercury. Assume Mercury is 0.52 AU from the Moon and that Mercury sees the Moon fully [it's a full moon]. Okay...

How to calculate the visual magnitude of a star having only the flux of such star? The equation involves 2 magnitudes and 2 fluxes, corresponding to 2 objects a and b: ma-mb= -2.5log10\left( \frac{F_a}{F_b}\right) but I just have Fa and I have to obtain ma. Is it valid to take...

Homework Statement What is the apparent magnitude of a 100W light bulb at a distance of 3 m? [Hint: Compare with the Sun to eliminate the unknown constant in the expression relating flux density to apparent magnitude.] . The solar luminosity is L \approx 4 \times 10^{26} W. . The Earth-Sun...

is that both of absolute and apparent magnitude counts only visible light? since i found some books said absolute magnitude counts luminosity instead of intensity, where luminosity includes also the non-visible frequencies. thank you!

Homework Statement A binary star system consists of a hot main sequence star (m=0.5m) and a red giant (m=1.2m), the parallax of the system is p=0.0012". Calculate the apparent magnitude of the system. Homework Equations I have b1/b2 = 2.512^(m2-m1) and p=1/r The Attempt at a...

Hi guys, first post (hopefully not only). If 2 stars are in an apparent binary system, how do you calculate the "combined apparent magnitude" of the system if you know both their apparent magnitudes and their distance from you. I can work out the apparent magnitude (even though that's not...

Homework Statement Two stars are in a circular visual binary system. The orbital period of the binary is 30 years. The distance to the binary is 20 parsecs. The angular radius of the orbit of each star is 1". What are the masses of the two stars? each star works out to be 4.4 solar...

Homework Statement During its lifetime a massive star converts about one solar mass of hydrogen into iron in its core, releasing about 0.7 percent of the rest-mass energy in the form of radiation. When it explodes as a supernovae, the outer envelope of the star (with a mass of 10Msun, say)...

Ummm... never mind, we found it... Homework Statement Given Proxima Centauri with parallax angle of 0.769" and apparent bolometric magnitude of 11.1... what is its absolute magnitude?Homework Equations I get that I should use m-M = 5 log10(d/10 pc) and I understand that d = 1/p". What I...

Homework Statement 2 solar type stars are in a close binary system. Each indivual star has an apparent brightness of m = 10 mag. Determine the apparent magnitudes of the combined system of the 2 stars assuming they cannot be resolved as individual objects. Determine the minimum brightness...

I am having trouble understanding this problem. It has several parts describing a binary star system. The last part ask for the apparent magnitude of the combined light from both stars, if they were viewed as a single point. I guess my first thought was to add them, but I'm worried because...

I've seen that Mars' apparent magnitude varies between -2.9 and 1.8 and Mercury's from -2.0 and 5.5 (wikipedia said so at least). I'm trying to figure out which planet would have the greatest variation in brightness, as seen from Earth. The numbers at wikipedia points in the direction of...

[SOLVED] Apparent magnitude of binary star? Homework Statement A binary star has a total apparent magnitude of 15.00. One component star is twice as bright as the other. a) Show that the apparent magnitude of the brighter star is 15.44. b) The fainter star has an apparent magnitude of...

Homework Statement What is the combined apparent magnitude o a binary system consisting of two stars of apparent magnitudes 3.0 and 4.0 Homework Equations m-n=2.5 log(f(m)/f(n)) The Attempt at a Solution I know m= 3 and n=4 ,or vice versa. I'm not sure what this problem means by...

What is the meaning of: "the apparent magnitude of a star is obtain with a system of 3 stars"? Thanks

Homework Statement Two stars have apparent magnitudes of V = 5.1 and V = 4.6 but are too close together to be resolved with the naked eye and appear to be a single object. What is its apparent magnitude? Homework Equations I don't know what the relevant equations are if there are any...

The extinction to our galactic center is about Av=20mag. What would be the apparent magnitude of our sun at the 8000parsec distance of the galactic center? From what I know, I think I need to use http://en.wikipedia.org/wiki/Absolute_magnitude#Computation the luminosity-distance formula. So...