Questions tagged [luminosity]

Questions regarding the amount of energy produced by an object per unit of time.

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46 views

Estimating a star's radius, temperature, and luminosity based on its mass

(See updated figure and description below.) I've been trying to generate ballpark estimates for the radius, temperature and luminosity of stars in the main sequence based solely on their masses (...
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45 views

How Wide Would the Habitable Zone Be in a Singular Red Giant System?

Astrobiologists looking for signs of life outside Earth usually take excitement over planets orbiting red giant stars because a larger, brighter star usually means a farther-away but still wider ...
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Why is the Sun's Luminosity not equal to the Zero Point Luminosity?

I was doing some research and found that the zero-point luminosity was $L_\odot = 3.75\times 10^{28} $, while the sun's reported luminosity was $L_{Sun} = 3.828\times 10^{26}$, according to Wikipedia. ...
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What Would Be the Maximum and Minimum Luminosities of a G-Type Main-Sequence Star?

So I just found the Habitable Zones in Multiple Star Systems interactive website, where I can create a habitable zone out of multiple stars using the temperature, luminosity, mass and position of each ...
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How to convert magnitude to spectral luminosity? [duplicate]

In the Gaia catalogue I have the magnitude of several stars in the G band. I also have the distances to these stars (parallax is known). Additionally, I oftentimes have the effective temperature in ...
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I need help with an equation for figuring out the surface temperature of Red Dwarf!

Say you have a 10 billion year old, slow rotating, quiescent M5 star with a mass of 0.32 M☉ , a luminosity of 0.018 L☉ and a burning (haha) desire to figure out the surface temperature. However you ...
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29 views

Converting the log (Stellar Luminosity/Solar Luminosity) and the log of the plus and minus variation

There are some stars in the NASA Exoplanet Archive that I am interested in but I am confused by the physical meaning of the terms. For example, there's a star BD+15 2940 with a log10 of Solar ...
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Q: Calculating the luminosity of a galaxy

I am currently working on a project on which I am calculating the luminosity of galaxies by using the SDSS data. They use a system of asinh magnitudes, and according to their website they use a system ...
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Stars that don't fit $L=4\pi R^{2}\sigma T^{4}$?

When calculating luminosity/radius/temperature for several stars, I've noticed that while the majority of stars conform to the luminosity relationship $L=4\pi R^{2}\sigma T^{4}$, there are a few that ...
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How to calculate the distance to galaxies with standard candles?

I was wondering how the distance in Mpc could be calculated between Earth and a galaxy using the luminosity provided? Do not be shy to use all math necessary :)
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How actively is Deep Learning being used in exoplanet identification?

Papers, like this one from Google, show that Deep Learning and Machine Learning are effective in detecting exoplanets from luminosity data provided by telescopes like TESS or Kepler. These models ...
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1answer
67 views

Eddington luminosity in various plasmas

So I know that the Eddington luminosity is given by: $L_{Eddington} = 4\pi GMc/\kappa$. I want to calculate this luminosity for a plasma of purely ionized helium, as well as for an electron-...
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Radiative Flux, Irradiance and Luminosity confusion

First of all I know there is a similar question here, but I feel is wasn't answered at all. My question is that I have seen many texts which says that Radiative Flux is equal to the Irradiance of a ...
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1answer
155 views

How to correct observed flux densities for redshift

Say I have a spectrum of a galaxy at a redshift $z$, in flux density units of erg/s/cm^2/Angstrom. I'd like to recover the spectrum (in the same flux density units) at z=0, i.e. at its rest ...
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Luminosity of the Milky Way compared to Seyfert galaxies

This page lists the total luminosity of the Milky Way Galaxy to be $4\times10^{10}$ $L_{sol}$, and $L_{sol}=3.86 \times10^{33}$ ergs.sec$^{-1}$; this gives a total luminosity for the MW of $1.54\...
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Conversion factors for flux

I have a flux value in the infrared band of 8 mJy at a wavelength of 80 microns that I want to translate into X-ray conventional ...
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What area of Proxima Centauri would need to be occluded for the effect to be observable on Earth?

One of ideas of how Breakthrough Starshot could communicate data from Proxima Centauri is to have a massive swarm of the solar sail powered craft to pivot (with their sails) synchronously, taking ...
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How can I estimate the M/L ratio from a fitted SED on a galaxy?

This answer (here in the forum) provides background to my question: https://astronomy.stackexchange.com/a/5953 I am trying to understand the process in which a stellar population synthesis (SPS) is ...
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86 views

H-R diagram, Double stars

Can someone help me? I have a case, like, we have H-R diagram and two stars on it. One of them is a blue star on main sequence, another is a red giant. They have equal luminosity. If they are in a ...
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What does this figure imply about the luminosity of pre-main-sequence stars?

Check out Figure 1 in http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1955PASP...67..154H&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf . It seems to ...
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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 $...
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Is it possible that quasars are not powered by black holes but some other kind of compact, massive object?

AFAIK, objects in the universe thought to be black holes show evidence of radiatively inefficient accretion flow. But is this the case with Quasars? If not, is there a possibility that the core of a ...
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How bright would it be on the “face” of Titan

If you were planing a maned mission to Titan and wanted to find a landing site that would get the most visible light for the longest amount of time, your first logical choice would be the dark side of ...
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Two lights roughly 5 minutes apart about as bright as Mars or maybe Saturn

I'm in the Minneapolis/St. Paul area and around 9:30 on August 4th 2017 I saw a bright light that got dimmer moving from the tree line to the east up and to my left fairly slowly, and steadily getting ...
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290 views

How to shift AGN x-ray spectrum to rest frame from

I have limited information to shift a spectrum (in the x-ray 0.5-10 keV bandpass) at redshift z=2 to rest frame. I have a plot of normalized (photon) counts s$^{−1}$ keV$^{−1}$ by energy (keV), and so ...
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What is the radiant intensity of the celestial sphere?

Specifically, excluding the Sun and the Moon: How much energy, as light and other frequencies reaches a point in space on the average, if you add up all the sources like distant stars, the Milky Way, ...
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1answer
458 views

What does Eddington Limit (Eddington Luminosity) Show?

We know Eddington Limit (Eddington Luminosity) is calculated with this formula: $$L_{Ed} \approx 3 * 10^4 * L_{sun} * \frac{M}{M_{sun}}$$ Example: For a black hole with $10^4 M_{sun}$, we get $$L_{...
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1answer
3k views

How to convert magnitudes to bolometric luminosity? [duplicate]

If we know a star's magnitudes from several bands(say u,g,r,i,z,J,H,k) and the star's distance, how to calculate Lbol? Let's suppose the star has a black body spectrum. Is there any manual about the ...
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Question about radiation pressure

A spaceship with mass $m = 25\:kg$ is moving toward a red giant with $M = M_{sun}$ and $L = 1000\:L_{sun}$ (L: Luminosity). It is moving on a line (so this is not an orbital question). When it gets ...
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181 views

Problem about finding distance with magnitude given

A star in Pleiades cluster has apparent magnitude of +12 ($m_{star} = +12$) determine it's distance from the sun? (We know the Sun properties such apparent and absolute magnitudes, distance from earth,...
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758 views

How to convert theoretical template spectrum from luminosity density to flux density units?

I'm working with galaxy spectral templates (e.g., Bruzual & Charlot 2003) which seem to always come with y-axis units of $L_{\odot}$/A and x-axis units of Angstroms. Thus the y-axis is a ...
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187 views

Why do different instrumental filters use different magnitude systems (Vega vs AB)?

Suppose I wanted to construct the spectral energy distribution (SED) of an object. Further suppose I observe this object through the 9 broad-band filters using the Subaru Suprimecam (just for an ...
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2k views

Difference between luminosity, luminous flux, and radiant flux?

I've looked this up, and was wondering the differences between them. Luminosity is the total energy emitted by a source, in watts. However, I'm confused about luminous flux and radiant flux. Since ...
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787 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 ...
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Calculate Luminosity of Vega

I want to calculate the Luminosity of a star e.g. Vega but can be any star and came across the formula for Luminosity at the University of Oregon (http://pages.uoregon.edu/soper/Light/luminosity.html)....
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697 views

Finding luminosity of a star with magnitude

I'm working on my assessment for Physics in the IB, and I'm planning to investigate stars in spiral galaxies and determine their ages. For this I'm going to use data from the SDSS (Sloan digital sky ...
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312 views

What characteristics or patterns do galaxies have on color-luminosity chart? [closed]

For the following graph, I have some confusions: How do galaxies rank by mass? We know that on main-sequence, more luminous stars are also more massive, so I guess it also applies to galaxies. Do red ...
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What is the spectral power output of a typical galaxy?

I'm looking for a function which gives the typical isotropic spectral power of light emitted by an entire galaxy on the whole electromagnetic spectrum (in watts per frequency unit), as a function of ...
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1answer
710 views

Flux density to flux

The definition of flux and flux density is fairly straightforward. However, I'm musing over the practical usage of it. For one thing, if you observe a source through a filter, how would one go from ...
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1answer
122 views

From color index to luminosity

Given two colorindices LX and LY, such that the color X-Y is given by X-Y = -2.5 log(LX/LY) is there a way to infer the luminosity in X (or Y)? I'm think not ...
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Solar luminosity proportional to $G^7$?

A book I recently purchased describes Dirac's proposed variation of Newton's G, and why that specific proposal wouldn't work because the earth would have been too hot for the known history of life. A ...
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Deriving phase of a pulsating star from list of Julian date values of observing brightness

I want to convert the list of Julian date values of observing brightness of a Cepheid variable into its phase. The equation I found in the Internet is the following: $$\mathrm{Phase}= \frac{\mathrm{...
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Change in angular diameter of Cepheid variables

I'm a highschool student and in the process of writing a research paper of deriving period-lumniosity relation of Cepheid variable independently of the pre-existing PL relation. Thus, I need to derive ...
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1answer
3k views

How can I convolve a template spectrum with a photometric filter response spectrum?

Suppose I have a template stellar population spectrum (say, from Bruzual & Charlot 2003) which runs from like 1000 Angstroms to 160,000 Angstroms and which has x-axis wavelength units of Angstroms ...
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Finding Mass of Star with only Luminosity [closed]

Estimate the mass of the star given this formula: $$\frac{L}{L_\mathrm{\odot}} = \left(\frac{M}{M_\mathrm{\odot}}\right)^{3.5}$$ Given $L= 2.752\times10^{28}\,\mathrm{W}$, how do I find the mass of ...
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110 views

The relation between the light of full moon and the distance between the sun and the earth

If we want the full moon to be 2 times more bright,how we should change the distance between the sun and the earth? Thanks for your help.
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465 views

What would be the apparent magnitude of Betelgeuse if it were as close to Earth as Sirius?

How large and bright would Betelgeuse appear if it were as close to Earth as Sirius, before and after it goes supernova?
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258 views

Color of planets

I am developing an astronomy software and need to know the color of each planet in the Solar System, when observed with the naked eye. I cannot find that information after googling for a while. Is ...
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139 views

Red dwarf variation in Luminosity

I recently saw this video. The creator of the video says that one of the reasons for non-existence of life on planets around red dwarfs might be that these stars can increase luminosity roughly by a ...
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What is the frequency distribution for luminosity classes in the Milky Way Galaxy?

I'm working on a game concept that does some mild simulation of realistic stellar classes and luminosities. In particular, I'd like to roughly model the general frequencies of the classes and ...