Questions tagged [spectroscopy]
Questions about the measurement of light waves whereby the wavelength is classified by its position in the electromagnetic spectrum.
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Spectrum of stars
If some specific metal is shown in a star's spectrum, does it indicate that the star has that specific metal? For example, the Sun, a G2 star, shows medium strength of Ionised Calcium in its spectrum, ...
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What is the best database for identification of spectral lines?
What is the best database for the identification of spectral lines? For instance, I have a red spectrum of A0 star and I would like to recognize the most prominent lines, where to find them? Many ...
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When examining an exoplanet's atmosphere is the star's emission spectra or planet's light used?
My understanding of the main method we use to figure out an exoplanet atmosphere composition is that when a exoplanet transits their sun, visible light passes through the planet's atmosphere, and ...
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What is a hard spectral state vs. a soft spectral state?
In X-ray astronomy, the source is considered to be in the hard or soft spectral state. So what is the meaning of the hard spectral state? What are the soft state and hard state in spectroscopy?
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Line Flux Ratios in Active galaxies
Good day to everyone.
I wanted to know what is the importance of estimation of line flux ratios in active galaxies? What does it help in characterizing?
As in Lyman $\alpha /$Carbon IV, or Mg II$/$...
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How are we identifying chemicals in space?
How do we identify chemicals in space? For example, how did we find the cloud of methyl alcohol (aka methanol) in W3 (OH) which is 6500 light years away. I can understand a scope being able to tell ...
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Are falling evaporating bodies (FEBs) and exocomets the same thing? How does one know they're falling and evaporating?
Looking for a (short) list of comets with heliocentric escape velocity I stumbled upon Wikipedia's exocoments which like exoplanets, are bound to other stars. I should have been looking for "...
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How can I know the source size using the spectrum variability?
When reading some astrophysical papers I saw things like this:
The sources are variable on very short timescales, implying a compact emission region.
How can we conclude or measure the source size, ...
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Missing line in solar spectrum
Referring to this answer to What's the rationale behind the false colours in solar observation photographs? which includes the table from Wikipedia's Fraunhofer lines:
In the Table of wavelengths ...
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Spectographically determine surface composition of exoplanet
We can determine the surface composition of a star by studying its spectrograph. If a exoplanet transits the star, then there is a slight change to the spectrograph, which lets us determine the ...
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How is spectroscopy used to deduce what an object is made of?
Spectroscopy is an analysis of light (or other EM wavelengths) that is often used by scientists to examine what an object is made from or contains.
Apologies if this is a stupid question, but this ...
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Phosphine on Venus?
For the purposes of this question, let's assume that the team really have detected phosphine.
My question is how do we know that phosphine is on Venus, and not closer to home?
I've just found out a ...
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What are the prospects for follow-up observations of phosphine on Venus?
Today, it was officially announced that astronomers have detected phosphine on Venus via the $\text{PH}_3(0\to1)$ transition (Greaves et al 2020). While the line was found by both the James Clerk ...
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Problem regarding the absorption lines of the Sun
Some of the wavelengths of light that are emitted from the Sun will be absorbed by atoms in the outer layer of the Sun and also the atmosphere of the Sun, and we see this as absorption lines in the ...
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How were "microshutters" or other multiplexed or multi-object techniques first used in Astronomical spectroscopy?
This answer to How will microshutter arrays be used in the James Webb and future space telescopes? explains how multiple objects can be selected so that the throughput of a spectrometer can be ...
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Can concentration of gas in exoplanet atmosphere be found out from wavelength and absorbing radius from spectral data?
I was working on exoplanet spectral data from which I need to infer the concentration of gases. However, the exoplanet spectroscopy data contains only absorption wavelength and absorption radius. Is ...
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How to search SIMBAD using identifiers?
I'm trying to get some data about the moon from SIMBAD (specifically, radiation spectrum in certain wavelengths), and I encountered an unexpected problem: I can't find the Moon.
In SIMBAD, I can ...
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MOOG 2019 and gfortran
I've been trying to install MOOG Nov2019 (utexas, Wiki) on my desktop running OpenSUSE 13.1. I have the SM and X11 library paths copied into the makefile, and I am 3-sigma confident that they are the ...
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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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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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How does a cross dispersed spectrum look like in a reality (from echelle spectrographs)?
I am an analytical chemist with some interest in amateur spectroscopy. Since astronomers use echelle spectrographs to study the high resolution spectrum of the stars, someone suggested to post the ...
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Is there a way to know if there are/are not solar-system-like systems of objects without a star?
There's an extremely high amount of variation in All of Known Existence. We do see many many stars, with an extensive amount of evidence for planets orbiting around stars. However, is there are way to ...
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How do astronomers detect the 'metals' in a star? If the atoms are presumably completely ionized?
Atoms and molecules usually emit their characteristic wavelengths because of the electrons' energy levels....
Do the completely ionized ('naked') nuclei absorb and/or emit EM radiation?
If so, at what ...
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Do free protons and neutrons absorb much radiation? To affect astronomers' observations? If so, at what wavelength(s)?
In a plasma, or wherever, do the completely ionized nuclei commonly absorb much EM radiation? Or any free neutrons or protons? Can astronomers detect this? Enough so that astronomers take it into ...
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What does "the depth of the 13.0 Å feature differs by 7 sigma from zero" mean?
In a paper I've read, I have seen the following:
In view of the noise levels, it is difficult to perform such a search effectively using statistical significance criteria only. We will therefore ...
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Were radio spectroscopic observations ever used to first measure a distance successfully?
Usually, especially for an extragalactic object, its redshift is determined by optical spectroscopic redshift. But the angular resolution of early radio observations is poor and an optical counterpart ...
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Blue color of ion (plasma) comet tails
What exactly is the cause of blue light of ion (plasma) tails of comets? Somewhere I have read that the source of blue light are CO+ ions which has just acquired the missing electron and became ...
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Specutils Gaussian1D fitter and estimators
I am running the "simple example" from specutils to do some line-fitting.
The demo code is here:
https://specutils.readthedocs.io/en/stable/fitting.html
This runs and does what it says.
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How to calculate the statistically significant level for a guassian line profile?
In some papers, they fit a line profile with gaussian model. For example, in
this paper, fig 1 draw three gauss line profile, O VII, O VIII, and Ne IX.
But the data seems noisy and the gaussian height ...
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Is there an all sky meteor watch with spectroscopy?
I assume performing spectroscopy on meteors would give us information about the composition of the outer layers of meteoroids, which we can't study on finds because it has already burned up. This ...
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Why N$_2$ is a non-absorbing species in the spectrum of the Earth?
The transmission spectrum of the Earth atmosphere is like that (Kaltenegger & Traub 2009):
As you can see, you can find many absorption lines related to some components of Earth's atmosphere: H$...
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Why are helium resonance lines called "resonance lines"?
Examples of the use of the term:
Formation of the helium extreme-UV resonance lines
On the Formation of the Resonance Lines of Helium in the Sun (unpaywalled)
Formation of the helium EUV resonance ...
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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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Identifying common galaxy spectral lines
How does one identify the common galaxy absorption lines (e.g. Na, Mg, K, etc.) and emission lines (H-alpha, O III, S II, etc.) by just looking at a galaxy spectrum (like the one below)? I need to ...
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Radial velocity curves
When I measure RV in a program for more spectral lines, will it be equivalent? I mean I measure RVs of a line in blue spectral region, RVs of a line in red spectral region... Many thanks.
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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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What is the physical interpretation of the derivative of the emitted and observed wavelength?
The flux F of an event at redshift $z$ is related to its luminosity L as
$$F=\dfrac{L}{4\pi d_L^2}\,,$$
where $d_L\equiv d_L(z)$ is the luminosity distance between us (the observer) and the event (...
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What is a "21cm/mm absorption system" in the context of measuring old photons from quasars?
This answer links to Wikipedia's Time-variation of fundamental constants which cites Further Evidence for Cosmological Evolution of the Fine Structure Constant (J. K. Webb et al. 2001), the abstract ...
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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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Convolve a SED with a filter. Is convoluting the mathematical operation?
I know that in order to get the Flux of a star (or something else) in a particular filter from its SED (luminosity per unit wavelength), I need to convolve the spectrum (SED) with the filter response. ...
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Nebula and its colors
A Nebula has bright awesome colors that include red, blue, green, orange, white, etc?
They're result of excitation of electrons.
Is there a clear explanation as to which color is attributed to an ...
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Did the late 2019 "fainting" of Betelgeuse show any spectral trends that differ from it's normal variability?
update: (August 2020) With all the newest news about including what the Dr. Becky video discusses as linked in How do magnetic fields mess with astronomers' observations? I'll bet this question ...
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Data for spectrum of Wolf-Rayet stars
I'm looking for a way to access the data used to produce these plots for instance. These plots show the spectrum of various Wolf-Rayet stars. I found a few websites where you have some informations on ...
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What is the difference between spectroscopy, spectrography and spectrometry?
Spectroscopy is the study of spectra, spectrography is the writing of the spectra, and spectrometry is the measure of spectra. So from an etymological perspective, there is no real difference between ...
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What is the difference between emission line and recombination line?
When an electron jumps from higher level to lower level a photon is emitted. This is seen as an emission line. But what exactly is a recombination line? I found them similar. Can you please tell me ...
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Finding the Uncertainty in a Spectral Line
Currently, I am doing a lab in school on atomic spectroscopy. After taking readings of strong emission lines of various elements, I have fit the data using a Voigt Profile function from lmfit. The ...
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How to calculate Equivalent Width of a spectrum with continuum at 0
I am trying to calculate the Equivalent Width of emission lines of a spectrum whose continuum is at 0, making the calculation of the EW impossible.
I have the spectrum of a transient in a galaxy, so ...
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How much does the stellar radius change if seen through different filters?
I know that the radius of a star should be different depending on the filter being used to do the observation. That is, the bluer the filter, the smaller the measured stellar radius. I know this ...
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How exactly will DESI simultaneously capture individual spectra from 5,000 galaxies using optical fibers?
The BBC News article Telescope tracks 35 million galaxies in Dark Energy hunt says:
The aim of the five-year programme is to shed light on Dark Energy - the mysterious force thought to drive an ...
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What is an "Off Rowland-circle Telescope"? Are there "On Rowland-circle Telescope" as well?
The NASA Goddard news item NASA to Demonstrate New Star-Watching Technology with Thousands of Tiny Shutters says:
The technology, called the Next-Generation Microshutter Array (NGMSA), will fly for ...
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