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 ...
Astrovis's user avatar
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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 ...
J minding's user avatar
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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 ...
SmilySunMike's user avatar
6 votes
1 answer
136 views

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 ...
CuriousCosmos's user avatar
2 votes
1 answer
41 views

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 ...
Vincent ISOZ's user avatar
2 votes
2 answers
190 views

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 ...
ROPROPE's user avatar
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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 ...
InvisibleParticle's user avatar
5 votes
1 answer
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 ...
JOAQUÍN HERNÁNDEZ's user avatar
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; ...
Cheng's user avatar
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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 ...
E.UCIT's user avatar
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2 answers
227 views

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 ...
Constantthin's user avatar
2 votes
1 answer
641 views

E(B-V) , the color excess between B and V bands, for galaxy at redshift 0

Following Mo et al. 2010 (page 479), the quantity $E(B-V)$, called the color excess between B and V bands, is equal to: $$E(B-V) = A_B - A_V = (B - V) - (B - V)_0 = (m_B - m_V) - (M_B- M_V)$$ where $...
fslack's user avatar
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How is the difference of bolometric magnitudes not dependent on the stars' radii?

The difference of 2 bolometric magnitudes is given by: $$M_{bol, ★} - M_{bol, ☉} = -2.5 \cdot \log \left( \frac{L_★}{L_☉} \right)$$ But Pogson's equation is: $$M_{bol, ★} - M_{bol, ☉} = -2.5 \cdot \...
Pedro Nogueira's user avatar
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Given that a color index ($B-V$) of star A is lower than that of Star B, What can we say about the stars?

The color index $B-V$ of the star is defined as $$B-V\equiv M_B-M_V$$ Let us suppose it's given $$(B-V)^{(A)}<(B-V)^{(B)}\Rightarrow M_B^A-M_V^A>M^B_B-M^B_V$$ The notations are a bit confusing, ...
Young Kindaichi's user avatar
2 votes
0 answers
39 views

Is it possible that absolute magnitude for two stars is equal for some wavelength?

The title explains the questions. I don't find any problem with it. As If the two stars A and B do have equal absolute magnitude for some wavelength $\lambda_0$ then $$M_A=M_B$$ $$-5(\log d_A-1)+m_A=-...
Young Kindaichi's user avatar
2 votes
1 answer
146 views

When calculating absolute magnitudes of distant objects, do you use the light-travel distance or the comoving distance?

I want to calculate the absolute magnitude of GN-z11. Its light-travel distance is 13.4 billion ly (4.1 Gpc), its comoving distance is 32 billion ly (9.8 Gpc), and its apparent magnitude is $25.8$. ...
WarpPrime's user avatar
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What spectral type of star has an absolute magnitude of exactly 0?

We know that Vega is the star that serves as the zero point for the UBV color scale, and has an apparent magnitude of nearly zero (+0.02). But its absolute magnitude is +0.58, making it rather far ...
WarpPrime's user avatar
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Calculate the absolute magnitude for a multi-star system

We know that the absolute magnitude of a single star can be calculated with the formulae: $$M_{\rm bol} = 4.75 -2.5 \log_{10} \left(\frac{L_*}{L_{\odot}}\right)\ ,$$ $$M = -2.5 \log_{10}(L_* / L_0),$$...
WarpPrime's user avatar
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Is there a formula for absolute magnitude that does not contain an apparent magnitude term?

I have a star that I need to calculate the absolute magnitude of. I am given the temperature, luminosity, radius, mass, and distance in light-years. So I am wondering, what is the formula to compute ...
WarpPrime's user avatar
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How can you determine the distance of a star using the magnitude equation?

In high school we are undergoing a short course about astronomy. It is stated that you can use the apparent and absolute magnitude (m, M) to get a distance (D) of a star, with the formula $$m - M = 5 \...
AnnoyinC's user avatar
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Apparent magnitude of a spherical body with specular, rather than diffuse reflectivity? How bright were Sputnik 1 and Vanguard 2?

How bright are geostationary satellites due to reflected sunlight? and Did Sputnik 1 tell us more than “beep”? What science was improved by information gained from its orbiting the Earth? now have me ...
uhoh's user avatar
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Which star has the lowest absolute magnitude?

I have seen many lists of stars with the most luminosity, mass, and temperature, but I have never seen one that is about absolute magnitude. So I'm wondering, which star has the lowest absolute ...
WarpPrime's user avatar
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3 votes
2 answers
302 views

Best way to simulate star sizes to scale in celestial sphere

Using the Hipparcos catalogue, I am trying to create a celestial sphere. As all the stars are a fixed distance from the centre of this sphere, the only way to differentiate the distances and magnitude ...
SidS's user avatar
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Distance and absolute brightness

This is an exercise from a text, I’m learning from and I can’t understand it so I’m asking just to develop my knowledge: The explosion of V603 Aql (Nova Aquilae) took place in June 1918. The nova ...
Paulina Góra's user avatar
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489 views

Is there a relationship between stars' absolute magnitude, spectral class and relative location in a cluster?

I am interested to know whether a pattern has been observed with regard to the characteristics of a star (in particular, its absolute magnitude and spectral class) and its location relative to others ...
POD's user avatar
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1 answer
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Distance to star using color index

I'm doing the following question: A star is observed with UBV magnitudes $m_u = 16.31$, $m_b = 14.52$, $m_v = 13.76$. Spectral analysis gives $M_{bol} = 7.31$, $BC = -1.02$, $(U − B)_0 = 1.222$. ...
Alistair's user avatar
3 votes
1 answer
1k views

How to convert luminosity at rest frame wavelength of 1450 A to absolute magnitude at 1450 A?

How do I convert the luminosity (erg sec$^{-1}$ Hz$^{-1}$) of a quasar at a rest frame wavelength of 1450 Angstroms to absolute magnitude at the same wavelength? I know that the bolometric ...
Arpan Das's user avatar
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0 votes
2 answers
394 views

Rendering stars in 3D space - AbsMag to OpenGL scale values

I am using the AMNH's Digital Universe stars.speck file to render stars in 3D space. The speck contains parsec-scale coortinates, where our Sun is at 0,0,0. It also lists the AbsMag values - i.e the ...
Rando Hinn's user avatar
2 votes
1 answer
171 views

How to interpret error of absolute magnitude of a star given data from wikipedia?

This Wikipedia page contains information about the star Spica in the rightmost table. A small snapshot of this table is below. In this table, the absolute magnitude is given as ...
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3 votes
1 answer
185 views

Snowball Earth brightness

The Earth likely froze over almost completely about 700 million years ago. This increased its albedo significantly, and I wonder if that would have a considerable effect on its apparent magnitude from ...
Simon Korneev's user avatar
1 vote
1 answer
236 views

Relationship between Hubble paramater and absolute magnitude

I have a set of data that is absolute magnitude of a star and its redshift. Is there any way to compute the value of the hubble parameter given that magnitude and redshift?
ac1643's user avatar
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Is albedo ever greater than unity? How is it calculated for various surface diffusivities and specular reflection? [duplicate]

I'm trying to understand how albedo would be calculated for a body with well-characterized surface reflectance properties, so that it's absolute magnitude could be defined. One could argue that this ...
uhoh's user avatar
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0 votes
2 answers
2k views

Conversion of UBVRIJHK magnitudes to luminosity?

So, I know that the standard for conversion from bolometric magnitude to luminosity established in 2015 equates to: L = 10^(-0.4 * magnitude) * 3.0128e28 Easy ...
KarenRei's user avatar
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1 answer
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Absolute magnitudes with dust extinction

I have a distant $z\sim3$ galaxy with absolute AB magnitudes $M_B$ and $M_I$, where the central wavelengths of the $B$ and $I$ passbands are $\sim0.4\,\mu\text{m}$ and $\sim0.8\,\mu\text{m}$, ...
ajrlewis's user avatar
5 votes
0 answers
56 views

In the JPL small body browser, why is uncertainty on absolute magnitude "N/A"?

In the JPL small body browser, orbital elements are all provided with uncertainties and even a covariance matrix, such as for 2013 LA2. Very good. But underneath, the absolute magnitude is reported ...
gerrit's user avatar
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3 votes
2 answers
2k views

Gaia Gbp - Grp: why does it get larger as star gets redder?

As an enthusiastic amateur scientist, I'm plowing my way through a cool Gaia DR2-based paper, "An Empirical Measurement of the Initial-Final Mass Relation with Gaia White Dwarfs". I'm doing all right, ...
Daniel Griscom's user avatar
4 votes
2 answers
746 views

Good source for the relationship between absolute magnitude, diameter, and albedo?

In this answer I have rearranged an equation from somewhere, and now I can not relocate the source. My re-aranged form is: $$M_{Abs} = 5 \left(\log_{10}(1329) -\frac{1}{2}\log_{10}(\text{albedo}) -\...
uhoh's user avatar
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4 votes
0 answers
83 views

Is there an acceptable value for the absolute magnitude of horizontal branch stars?

I'm writing a test for a gen-ed level astronomy class that I teach, and would just like a good reliable number to use as the basis for a distance calculation question. And yes, I know that real ...
dmckee --- ex-moderator kitten's user avatar
1 vote
1 answer
89 views

Mass-magnitude relation of evolved stars

In short: what mass is appropriate for absolute magnitude $M_V \sim -7$? Some context: I'm processing the observational data (supernova light curve) and curve fitting gives me about $0.4M_\bigodot$ ...
Tajimura's user avatar
  • 177
6 votes
1 answer
5k views

How to calculate luminosity in g-band from absolute AB magnitude and luminosity distance?

How can I calculate the (non-bolometric) luminosity $L$ of a galaxy (or a star for that matter) over a given band from its AB apparent magnitude $m_{AB}$ over that band and its luminosity distance $...
Miladiouss's user avatar
3 votes
2 answers
6k views

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/...
Awoogamuffin's user avatar
1 vote
1 answer
2k views

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 ...
Potato Comet's user avatar
32 votes
3 answers
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?
Patrick's user avatar
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3 votes
2 answers
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Table of absolute magnitudes of stars by spectral type and photometric band

I would like to find a table where I can, say, look for K5 dwarfs and read off that stars of that type have on average an absolute magnitude of X.XX in the infrared L band and Y.YY in the G band. I've ...
TheBigH's user avatar
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1 vote
1 answer
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Absolute/apparent magnitude and distance for HIP31978 inconsistent?

EDIT: I am still following up, but here's the latest response from Wolfram: Paclet servers are updated and optimized for each version of Mathematica, so I suspect you may be working on an older ...
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