# Questions tagged [absolute-magnitude]

Use this tag for questions that are about the brightness of a celestial object as seen from 10 parsecs away.

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### Is there a specific constant name for the fifth root of 100?

I understand that each scale you go up on the absolute magnitude scale, the luminosity decreases by the fifth root of 100, or around 2.512. Is there a name for the constant 2.512, or not. Also, is the ...
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### Query spectral type for absolute magnitude

I'm working on a project with stars where, given their spectral type (such as B0IV), I want to be able to know its approximate absolute magnitude. I have searched online and found data sources like ...
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### Why was the standard distance set to 10 parsec and not simply to 1 parsec?

On closer inspection of the absolute visual magnitude and the apparent visual magnitude of the sun, I noticed that their magnitude range (4.83 + 26.74 = 31.57) exactly matches the human eye. The ...
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### How to Determine Absolute Magnitude of a Galaxy using HST FITS Image

I'm attempting my first serious research project but due to... various circumstances, I am going to mostly be solving problems like this on my own with minimal outside help. As for the actual problem, ...
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### Calculating the absolute magnitude of a solar system body

I am trying to calculate the absolute magnitude of a solar system object, given its albedo, and assuming all of its luminosity comes from reflecting light from the sun. Using $L_{sun}$ = solar ...
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### Standard definitions (ISO?) about subjects related to light emitted by stars

I'm a big fan of astrophysics and astronomy. However i'm quite confused by reading these last years plenty of books on the subject with various definitions (vocabulary) and notations for the same ...
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### Finding the absolute magnitude of a star as a fraction/multiple of the Sun's absolute magnitude

This is a homework-related question. I am trying to find the spectral class and luminosity (relative to the Sun) of a star using its absolute magnitude. The absolute magnitude is expressed as a ...
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### calculate the absolute and apparent magnitude for a binary star system

I'm used to use this formula to find the apparent magnitude of a star $$m_1 - m_2 = -2.5 log(\frac{f_1}{f_2})$$ If both star are at the same distance from us and their luminosity is the same, does it ...
316 views

### Surface Brightness Definition

I know the surface brightness is calculated by taking the apparent magnitude of an object and then divide by the size of the thing. But this is more of "observed" surface brightness, how do ...
1 vote
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### (Wikipedia) UY Scuti: variable apparent magnitude, non-variable absolute magnitude?

According to https://en.wikipedia.org/wiki/UY_Scuti Apparent magnitude (V) 8.29 - 10.56 Absolute magnitude (MV) −6.2 UY Scuti, being a variable star, obviously has variable apparent magnitude; ...
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### absolute magnitude of an asteroid

I've done some research and found that one could derive the absolute magnitude $H$ of an asteroid in the following way. $H$ is the brightness of the asteroid, observed on Earth, if the asteroid were ...
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### How to calculate absolute magnitude of planets?

Knowing: Star's radius $r_s$ , luminosity $L_s$, and absolute magnitude $V$ Planet's radius $r_p$ , albedo $a$ , and distance $d_s$ How can you calculate the absolute magnitude of a planet in a ...
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### What is 5 in 5log10 the value of?

I know what 2.5 stand for in $2.5 \log_{10}$, but what does the number 5 in $5\log_{10}$ stand for and what application does it have. Thus, why is the number a five and not a four, or a three, or ...
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### Calculating star radius from temperature and absolute magnitude - what am I missing?

In an attempt to visualise nearby stars, I've tried to get the star radius (measured in solar radii) using the equation provided on the following site: http://cas.sdss.org/dr4/en/proj/advanced/hr/...
1 vote
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### How to find a Cepheid's pulsation period using its graph?

Basically, I've been seeing these graphs that say: Cepheid Period-Luminosity Relation and the Period axis is supposed to be "logarithmic"; How does this graph work? Since the luminosity of a star ...
6k views

### Is the Sun visible from Proxima Centauri to human eyes?

I know that the light coming from Proxima Centauri is not bright enough to make it naked-eye visible from the Earth. Is the Sun naked-eye visible from Proxima Centauri?
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