Questions tagged [luminosity]

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

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How can I convert luminosity from [erg/s/Hz] to [erg/s]

I have the dust-corrected luminosity in the Ks band in the unit erg/s/Hz. I want to convert it to erg/s. I would like to know which method is correct: $L[erg/s]=L[erg/s/Hz]\times(C/\lambda)$ $L[erg/s]...
Fatemeh Abedini's user avatar
1 vote
1 answer
91 views

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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4 votes
1 answer
123 views

Wien's law gives two different results?

Say I have a star with radius $R$ and luminosity $L$. I want to find the frequency of its peak emission. Taking the star as a perfect blackbody, we can use Stefan-Boltzman to see that $$L = 4\pi R^2\...
Captain Chicky's user avatar
1 vote
0 answers
47 views

Calculate Luminosity of a star from the Hipparcos catalogue

Is it possible to calculate the star's luminosity based on the data in the Hipparcos catalogue? Currently I'm using this algorithm, I have even fitted the bolometric correction to the Johnson V band (...
someCO_OLguy's user avatar
1 vote
0 answers
69 views

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
1k views

Confusion over habitable zone

I am confused over the habitable zone, as I calculated the expected temperature of Earth (minus greenhouse effects), and it would be -17 C. Which is below the freezing point of water. I also made a ...
DanceroftheStars's user avatar
1 vote
1 answer
255 views

Is there a way to calculate a star's luminosity from its apparent magnitude?

I was wondering if there's a way to calculate a star's luminosity from apparent magnitude data.
Nam's user avatar
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3 votes
1 answer
152 views

Period-Luminosity Relation of Cepheids via Gaia Data

I was trying to verify Leavitt's Law of Period Luminosity Relationships of Cepheid Variables using Gaia data. To do this I calculated the period using the Lomb Scargle Periodogram for 1450 stars and ...
Ambica Govind's user avatar
1 vote
0 answers
22 views

Using Gaia Passbands with L_nu coordinates

I am trying to find the coordinates of my bundles of gas on the gaia ($G, G_{bp}-G_{rp}$) hr diagram. I have its spectrum in $\nu L_\nu$ coordinates. Thus far, my attempts have mainly been to ...
Berkin's user avatar
  • 53
4 votes
1 answer
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What's the relation between the parallax distance and the luminosity distance?

I have read that Riess and his team are able to measure $H_0$ from supernovae calibrated using Cepheid in a model independent way. from what I have gathered they find the absolute luminosity of ...
Alucard's user avatar
  • 143
1 vote
1 answer
333 views

Help converting Jansky/beam to erg s^-1

I have some radio observation data in jansky/beam from NVSS at 1.4GHZ, and I want to convert these values into luminosity values (erg/sec). I have the distance data and I made a formula to convert it: ...
Ege Tunç's user avatar
1 vote
1 answer
397 views

How to convert Flux Density to Flux?

I have a radio catalogue with flux density values. (Jy/bm) I'm confused converting this value to flux. Because I want to calculate luminosity, I need flux values. The unit made me confused. Since I ...
Ege Tunç's user avatar
3 votes
1 answer
57 views

Protoplanetary disk luminosity - looking for a sanity check please

I've been told to "consider an Earth-mass of interplanetary grains (roughly spherical with a radius of a few microns) in a protoplanetary disk. Let the particles be in a torus with a cross-...
Chris M's user avatar
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1 vote
0 answers
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Magnitude cuts in different bands/surveys

I have data on around 142,000 galaxies. Some of these galaxies have apparent magnitude data in different bands. For example, many of my galaxies have SDSS PSF data in ugriz bands,GALEX FUV, GALEX NUV, ...
Bobasheto's user avatar
15 votes
6 answers
4k views

What's the issue with Olbers' paradox?

I'm not quite grasping the reasoning behind Olbers' Paradox, or why an eternal, non-expanding and spatially infinite universe would be incompatible with a dark sky. For simplicity, let's suppose that ...
Alex Popescu's user avatar
3 votes
0 answers
114 views

What is the average and the median mass and luminosity of a star?

I've heard in many places that the Sun is an average star, but in Wikipedia it says that about 75% of stars are M-type stars that are way less massive and fainter that the Sun. So how massive and ...
HugoF's user avatar
  • 186
3 votes
1 answer
107 views

How do I determine the Luminosity with a half-life decay?

I know there is a proportionality between the luminosity and $\frac{dN}{dt}$, but I am not sure why they are proportional and why there is a need for an initial mass to compute the luminosity if the ...
Casper's user avatar
  • 41
5 votes
2 answers
542 views

What is the infrared self-luminosity value of Jupiter and Saturn?

I'm looking for these data to apply them to the Kelvin-Helmholtz mechanism but I can't find the values. Or at least if there is an order of magnitude compared to the solar luminosity.
User13122015's user avatar
9 votes
2 answers
2k views

How bright will Alpha Centauri A be from Earth when it becomes a red giant?

As of right now, both stars from Alpha Centauri are in their main sequence stages, but eventually Alpha Centauri A is going to quickly expand in a matter of time, and I’m pretty sure its luminosity is ...
Prince Pugs's user avatar
1 vote
0 answers
45 views

How can I estimate a stars surface temperature, luminosity, radius, and lifetime only knowing it's solar mass and peak wavelength? [duplicate]

For example: if a 10 solar mass star emits light at a peak wavelength of λ = 300nm. How can I calculate a stars surface temperature, luminosity, radius, and lifetime with this infomation?
R-802's user avatar
  • 57
2 votes
1 answer
398 views

How can I calculate the luminosity and mass of a star only knowing it's peak wavelength and it's subtended angle?

For example if a certain star subtends an angle of 32 arcminutes at the Earth’s orbit and it's light has a peak wavelength of 500 nm, how can I find the luminosity and mass of that star?
R-802's user avatar
  • 57
2 votes
1 answer
104 views

Change in Luminosity of a planet

When viewed from the sun, the brightness of the planet with a given size and albedo changes according to the fourth power of inverse distance. I found the statement in one encyclopedia but I can't ...
Particle king's user avatar
1 vote
1 answer
199 views

Is luminosity distance related to both heliocentric redshift and CMB restframe redshift?

The luminosity distance $$d_l=(1+z)r(z)\ ,$$ where $r(z)$ is given by $$r(z)=cH^{-1}_0\int_{0}^{z}\frac{dz'}{E(z')}\ .$$ When I use the SNe dataset "Pantheon", I find there are two redshifts:...
user578569's user avatar
3 votes
1 answer
165 views

On finding the magnitude of Stars

I am wondering how I would be able to predict the Magnitude of fictional stars, given we know enough about them. As the formulae I can find online are mostly getting overly high values that don't seem ...
Zoey's user avatar
  • 131
3 votes
0 answers
593 views

DIY Sky Quality Meter: Conversion between Illuminance and Luminance

I am trying to create a homemade Sky Quality Meter (SQM) using a TSL2591 light sensor. This sensor measures Illumination (lux), but SQMs measure Luminance (mpsas). I have seen that there are many ...
Boube's user avatar
  • 31
0 votes
0 answers
114 views

How luminous does a brown dwarf have to be to illuminate an Earth-sized planet with 0.5 lux at 2,000,000 kilometers away?

A brown dwarf is a deuterium-fusing substellar object, and, in the cases of the larger ones, a lithium-fusing one. They often emit electromagnetic radiation in frequencies that humans cannot see. ...
KEY_ABRADE's user avatar
1 vote
3 answers
525 views

Calculating the luminosity of a comet

Assuming a 9-km comet is heading towards the Earth and it is at distance 5.2 AU away from the Sun, what is its luminosity? Assume that it has an albedo of 0.5? For now, I have calculated the Sun's ...
AmeliaGrace's user avatar
2 votes
2 answers
127 views

Finding stellar radii

Is apparent magnitude of star, distance(in pc) and effective temperature enough to calculate its stellar radii or we need some extra information?
Particle king's user avatar
7 votes
1 answer
495 views

Measuring the mass of the luminous matter in a galaxy

The mass of total matter in a galaxy can be measured using the rotation curve of the galaxy. However, how do people determine the mass of luminous matter in the galaxy, as a function of the distance ...
Nownuri's user avatar
  • 227
4 votes
2 answers
197 views

Brightness and flux density

The alpha star in a constellation has the highest brightness, but does that mean it has the highest flux density among the other stars in the constellation?
LAKSHYA ANILKUMAR's user avatar
-1 votes
1 answer
230 views

How to find luminosity from a light curve? [closed]

I am currently trying to find the luminosity from the light curve. I have the data about the distance, counts/sec and the energy range in which it is measured for an object. What equation can be used ...
karthik gananath's user avatar
5 votes
3 answers
1k views

Could a black hole's accretion disk be bright through natural means?

This question is based on this description of the Cormoran Supermassive Black Hole in the Orion Arm's website: Surrounding this event horizon is an (apparently artificial) accretion disk about 4AU in ...
JohnWDailey's user avatar
5 votes
1 answer
199 views

What does a + (plus) mean in stellar classification?

I've noticed some stellar classifications might look like this: A0IV+G: (HD 70003) F3IV+F0IV (HD 82434) ...
aggregate1166877's user avatar
11 votes
1 answer
1k views

Spectral class and luminosity of hydrogen bomb explosions?

Since hydrogen bombs detonating are like tiny little stars, I wonder what luminosity and spectral classification they would get if one were to categorize them like this. E.g. Starfish Prime and the ...
John's user avatar
  • 1,538
2 votes
0 answers
267 views

How to calculate rest-frame luminosity in a specific wavelength band?

For instance, I have a set of templates whose y is in Jy and x is in Angstroms. I have both of their rest-frame and obs-frame wavelength (i.e. redshift). I want to know their luminosity in one ...
B1GeasY's user avatar
  • 21
4 votes
1 answer
217 views

Is it dangerous to look at an L-type brown dwarf from too close?

Are some L-type brown dwarves bright enough so that it would be dangerous to the eyes if one looked at them from habitable distance or closer? If not, are the weakest M-type stars undangerous to look ...
Giovanni's user avatar
  • 145
3 votes
1 answer
133 views

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
1 vote
1 answer
211 views

HR diagram x-axis (color) and redshift?

I've read several articles and watched some videos on the HR diagram, but no-one seems to mention the effect of redshift on the color of a star. Is there some calibration step that needs to be applied ...
captcha's user avatar
  • 113
1 vote
1 answer
90 views

Is something wrong with my luminosity calculation?

A few million years after a white dwarf forms, its surface temperature reaches $100000\text{K}$, while its radius is $0.01R_\odot$. Would this mean that its luminosity is $\Big(\dfrac{100000}{5778}\...
WarpPrime's user avatar
  • 6,653
0 votes
1 answer
546 views

How to calculate galaxy bolometric luminosity?

I am a bit confused by bolometric corrections. If I have an x-ray luminosity in the 2-10 keV band, how does one convert that to $L_{bol}$? From Netzer's book The Physics and Evolution of Active ...
theWrongAlice's user avatar
1 vote
0 answers
989 views

Schechter Luminosity Function fitting plot of galaxies

I would like to plot the Schechter Luminosity function of galaxies. Here is my data(I have the Luminosity L[Ha] in erg/s). I would like to plot like this figure from this paper. In this paper, they ...
astronerd's user avatar
1 vote
1 answer
72 views

Estimating Sun luminosity from first principles

In a lecture, it was claimed that luminosity can be estimated by dividing how much energy there is in the Sun with the typical time it takes for a photon to get out from the centre of the Sun to its ...
zabop's user avatar
  • 481
1 vote
0 answers
25 views

Equilibrium Temperature for Extremely Cold Planets: Incorporating the CMB and Intrinsic Radiation

I want to check if I'm doing this right. I'm computing the equilibrium temperature for planets where the CMB and/or the planet's intrinsic radiation (as in weakly radiating jovians) matters. I start ...
MackTuesday's user avatar
1 vote
1 answer
75 views

Does photon capture in a black hole (or any other "very compact" object) reduce the luminosity/photon flux from its self isotropic emission?

I don't know if this is even a feasible question or if I have a point in asking so. Let's say we can model the radiation coming from a very compact object, such as a BH with an accretion disc or any ...
omivela17's user avatar
  • 201
1 vote
1 answer
334 views

How to obtain a luminosity from an SED

I have a spectral energy distribution (flux densities measured at several frequencies), and have fitted a 'greybody' model to these points. I am confused about how I use this information to determine ...
jm22b's user avatar
  • 147
1 vote
1 answer
622 views

What units are used for the Stefan-Boltzmann law?

I have a star with given temperature in Kelvin and radius in solar radii. I tried to calculate the luminosity of the star using Stefan Boltzmann's law, and got an absurd number (over 1 million). What ...
WarpPrime's user avatar
  • 6,653
9 votes
1 answer
1k views

Increase in Luminosity of the star

The Luminosity of a star is proportional to the 4 th power of its temperature and square of its radius. Also the mass-luminosity relationship says that the luminosity of star is proportional to ...
Dhruv Deshmukh's user avatar
3 votes
1 answer
80 views

Luminosity of Neowise

So, I have been trying to figure out the bolometric luminosity of the comet C/2020 F3 (Neowise) on the 22nd of June, 2020. At that time, Neowise was $1.4$ AU away from Earth and had an apparent ...
space nerd's user avatar
0 votes
0 answers
89 views

Samples from the double Schechter luminosity funcion

I want to produce samples from a double Schechter luminosity function. Ideally, I am looking for a python implementation of this problem but am open to other tools if necessary. Do you know of any ...
jm22b's user avatar
  • 147