# Questions tagged [extinction]

for questions regarding the dimming of light from distant objects when it passes through interstellar dust and gas clouds. This is not for questions about extinctions of species on Earth or other planets.

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### Why does infrared pass through clouds of gas and dust with minimal extinction?

Why do we use Infrared to view through clouds of gas and dust in space? I understand that it is because it can pass through without being absorbed, but why is this? My thinking is that it is because ...
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### Extinction Level Event (Asteroid Impact Hypothesis) Likelihood Equation

We have the Drake Equation that calculates the probability of intelligent ET (extraterrestrials/aliens). Since the asteroid impact hypothesis has been more or less accepted as the cause of the K-Pg ...
• 353
1 vote
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### Extinction coefficients for narrow band filters

does anyone know the extinction coefficients for hydrogen alpha, oxygen III and sulphur II narrow band filters? I easily found the coeffs for BVRI filters but can't find info on narrowband filters. ...
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1 vote
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### Internal extinction calculation

I am estimating the internal extinction of a spiral-barred galaxy (rest frame extinction). I use UV images to study the galaxy. I have Balmer decrement values of individual knots using which, I ...
• 304
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### What object(s) are furthest above/below the galactic plane?

This is kind of a spin-off of a question I did about a space telescope surveying the galaxy from above the galactic plane. So, it made me wonder, which object in the Milky Way has been spotted ...
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### Clarification on calculating IR Dust Extinction $A_K$/$A_V$

So I'm calculating V_Alf Ori's Luminosity (or Betelgeuse) using Davies et al. (2013) SED fitted formula from Near-Infrared/NIR K-Band magnitudes and it requires the subtraction of 'extinction'. ...
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### Determining the extinction by counting stars?

Hi I'm a highschool student studying astronomy at school. I learned that one can determine how much a luminosity of a star is reduced by counting stars, but I can't understand how it works. My ...
• 295
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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 $M_{bol} = 7.31$, $BC = -1.02$, $(U − B)_0 = 1.222$. ...
• 65
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### Color index B-V of the dimming Betelgeuse

Using AAVSO light curve generator I have plotted V and B magnitudes of Betelgeuse in the past 150 days to see trend of B-V color index. If dust would be the cause of the recent drop in the star ...
• 1,074
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### How to evaluate the fit of an isochrone to a stellar population?

Consider that I know the extinction, distance modulus, reddening, and metallicity for a particular star cluster. I need to determine it's age from isochrone fitting. After generating the required ...
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### Extinction and reddening dataset

Where can I find a dataset containing the interstellar reddening and extinction values for all globular clusters, preferably in the HST/WFC3 system.
• 333
1 vote
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### Difference in observing hot stars that have been reddened and stars that are cool and red

How do astronomers distinguish hot stars, reddened by the interstellar light absorption, from the actual cold red stars?
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### Clarity on dust extinction terms and implementation: $R_V$,$A_V$, and $E(B-V)$

I have created a model galaxy spectrum using STARBURST99 and want to compare it to an observed spectrum of a particular galaxy. I understand that I need to redden ...
512 views

### How to obtain distance modulus and Total extinction from Isochrone fitting to CMD?

This is my first post here. I am studying the following article: https://arxiv.org/abs/1901.03574. On Page 5, Sec 3.1, the authors are presenting their results they obtained via Isochrone fitting ...
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### Quesions about extinction power law

I am curious to know If dust extinction were to vary as a power-law so that $A_{\lambda}$ proportionate to $\lambda^{\beta}$ , what value of beta would give rise to Rv =3.1 which is the average in ...
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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 $\sim0.8\,\mu\text{m}$, ...
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### At what wavelengths can black hole Sagittarius A* be observed from Earth?

The supermassive black hole in the center of the Milky Way is blocked by dust and gas clouds as seen from where we are. Which wavelengths are blocked and which are most undisturbed for observation of ...
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1 vote
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### Interstellar reddening for Cepheids

How were interstellar reddening values for cepheid first calculated? I mean, other than using the derived equation to get extinction-corrected magnitude of Cepheids, I want to know how to drive them ...
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### Estimating galactic dust extinction for medium band filters

I have a set of medium-band filters and I would like to compute $A_{\lambda}/E(B-V)$ for each filter which are not reported in the literatures. The magnitudes of the objects in the photometry ...
• 261
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### How does one find the extinction coefficient of a particular galaxy? [closed]

I am doing photometry on a number of objects in a number of different galaxies. I need the extinction coefficients for these galaxies for various filters passes. Is there some database that displays ...
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### Speed of light through the ISM and Wavelength

Articles written about fast radio bursts describe the signal's short-wavelength components arriving before its longer-wavelength components, suggesting energy-dependent time delays in the interstellar ...
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### Galactic extinction as a function of distance

I am looking at several galactic sources in the $I$, $R$ and $V$ bands and I want to calculate their absolute magnitudes. I can get the apparent magnitude and I know the distance so I just need to ...
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1 vote