Unanswered Questions
108 questions with no upvoted or accepted answers
7
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Get the expression of probed volume between 2 redshifts
1) I can't manage to find/justify the relation (1) below, from the common relation (2) of a volume.
2) It seems the variable r is actually the comoving distance and not comoving coordinates (with ...
CommunityBot
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6
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0
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194
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What are the pros and cons of different types of echelle spectrograph cross-dispersers?
Echelle spectrographs, operating at high resolving power, typically consist of an echelle grating with a low numbers of lines/mm, used with high diffraction orders (often $n=$50-100). To separate the ...
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6
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Need help understanding stellar spectroscopy data from ESO
The European Southern Observatory webpage has a web page that has tabular spectrogram data from A. J. Pickles, University of Hawaii. There are over 130 .dat files there. Each one represents a ...
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6
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1
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Do narrow lines in the spectra of O- and B- type stars always indicate magnetic fields?
I was reading a paper on the differential emission measures of a set of hot O- and B- type stars. As the authors discuss in Section 3 (page 959), two stars, $\tau$ Sco and $\theta^1$ Ori C, have ...
CommunityBot
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5
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513
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How far away must galaxies be before current telescopes can no longer measure how quickly they are rotating around one another or internally?
What is the distance limit and does it depend on the size of the galaxy and on noise and interference from gas clouds and our own Milky Way?
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5
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457
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Why does titanium oxide around Betelgeuse produce this particular sawtooth-shaped absorption spectrum?
Betelgeuse Just Isn’t That Cool: Effective Temperature Alone Cannot Explain the Recent Dimming of Betelgeuse suggests that the recent dimming might be caused by increased optical absorption by dust ...
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4
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52
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How does SDSS estimate photometric redshift of sources?
I'm looking through the data in SDSS DR 12:
...
- 2,620
4
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54
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What happens to the non-fusion formed metals in stars?
Let’s consider a population I star of some given metallicity.
I know that depending on the type of star, different structures are possible with convection zones and radiative zones trading around ...
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4
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How are plage regions related to the density of medium and velocity FeII ions?
During a literature review (abstract), I found that the intensity of FeII (298.5 nm) ions in the last solar minimum was higher than the two previous solar minima 21 & 22. The velocity of FeII ions ...
- 30.7k
4
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0
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71
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K-correction vs resizing photometric bands
Is there a difference between a K-correction (see Wiki https://en.wikipedia.org/wiki/K_correction) and simply "resizing" the bands, e.g. the 2-10 keV x-ray band, with the redshift? I've read ...
- 30.7k
4
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What can Jupiter's spectrograph tell us other than its rotational velocity?
I have data of a Jupiter's image and the spectra of each pixel in the image, and I am playing around to see what I can do with it.
I have managed to find Jupiter's rotational velocity by finding the ...
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4
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0
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588
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A simple echelle spectrograph for viewing solar spectrum
On the Astrosurf website here, someone has designed a deceptively simple echelle spectrograph for viewing solar spectrum. Briefly, light from an optical fiber falls on an echelle grating and which is ...
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4
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57
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How is the roll of the Hubble telescope around its axis and the dispersive direction(s) of it's spectrometer(s) managed?
Reading Dupree et al. 2020 Spatially Resolved Ultraviolet Spectroscopy of the Great Dimming of Betelgeuse (also in arXiv and summarized in Phys.org's Hubble finds that Betelgeuse's mysterious dimming ...
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4
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69
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How significant is the effect of galactic rotation on line broadening of carbon monoxide?
In class the other day, we were discussing observations of rotational transitions of carbon monoxide, namely, the $J=1\to0$ and $J=2\to1$ lines. We originally had assumed that both lines would have ...
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4
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0
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210
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How to calculate magnitudes in photometry?
I have a passband filter $b$ and a spectrum (SED) $f_{\lambda}(\lambda)$. Often the formula I find to get the flux in that filter $F_b$ is
$$F_{b}=\dfrac{\int f_{\lambda}(\lambda) T_{b}(\lambda)d\...
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