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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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19 votes
2 answers
1k views

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 ...
User3141's user avatar
  • 319
16 votes
3 answers
3k views

Is it possible to measure galactic red shift using consumer telescope equipment?

I was wondering if it would be possible to measure red shift from distant galaxies using consumer grade telescope equipment and spectroscopy filters. (like this one) I imagine it would require a ...
asawyer's user avatar
  • 313
15 votes
3 answers
3k views

Formation of elements in the Sun other than helium

I just learned that the Fraunhofer lines of the Sun's spectrum indicate that the Sun contains various elements other than just hydrogen and helium (for example, Na and Fe) but don't the Sun's p-p ...
Jack the Ranger's user avatar
14 votes
1 answer
914 views

What happened to the reemitted photons during recombination?

To my understanding, the Cosmic Microwave Background Radiation (CMBR) is light released during the recombination epoch where the formation of neutral hydrogen atoms allowed for a sudden drop in the ...
YiFan's user avatar
  • 558
14 votes
2 answers
335 views

Strange bump in solar spectrum taken with home-made spectrograph

I am an astronomy teacher, and made some kind of spectrograph with a difraction grating, a 3D printed slit, water pipes and a reflex camera. With a group of students we got this picture of the solar ...
Luis López's user avatar
13 votes
2 answers
7k views

How does one determine the effective temperature of a star from its spectrum?

Determining effective temperature of a star is in general a non-trivial task. Simple reason for this is that we can only study the electromagnetic radiation from a star, but not the temperature ...
Alexey Bobrick's user avatar
12 votes
1 answer
335 views

Is any consensus forming on the solution to the "Lithium Problem"?

The "Lithium Problem" relates to the fact very-low-metallicity stars appear to have a Li/H ratio approximately one third of what would be expected. The ratio should be the same as the prediction from ...
Eubie Drew's user avatar
  • 1,080
12 votes
2 answers
758 views

How has the resolution of astronomical spectrographs improved over time?

Is there something like a Moore's law for spectral resolution? Maybe a chart from which one could extrapolate?
2080's user avatar
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11 votes
2 answers
2k views

How would a person know if a planet is orbiting a binary star?

I read in Neil deGrasse Tyson's book Astrophysics for People in a Hurry that scientists can tell if a star has a planet orbiting it because the light appears to shake. So if in the case of a binary ...
Tardy's user avatar
  • 255
11 votes
1 answer
532 views

How do astronomers calibrate the intensity scale of their spectrometers?

Discussion on Strange bump in solar spectrum taken with home-made spectrograph made me wonder: How do astronomers calibrate the intensity scale of their spectrometers? I mean, how to take in ...
Luis López's user avatar
10 votes
2 answers
1k views

Where in a star are the spectral absorption lines formed?

This question was inspired by a recent Cool Worlds video "The Star That Shouldn't Exist", in which one of the speculative solutions to Przybylski’s Star's strange spectrum is aliens "...
asgallant's user avatar
  • 571
10 votes
1 answer
944 views

Recording Spectral Lines at Home

I was wondering if it would be possible to record the emission/absorption spectra of stars without expensive spectroscopy equipment. Would it be possible to somehow utilize diffraction grating? I own ...
N. Bar's user avatar
  • 203
9 votes
3 answers
865 views

Why does Gaia use only calcium NIR lines for stellar radial velocity measurements?

I was reading this overview article about the Gaia spacecraft and I saw the following statement: These spectra provide radial velocity information that are used to study the kinematic and dynamic ...
uhoh's user avatar
  • 30.6k
9 votes
1 answer
581 views

What does "Effective radius of [CII] line is 1.4 kpc" mean?

A recent paper (A dusty compact object bridging galaxies and quasars at cosmic dawn) describes one of their results as the "Effective radius of [CII] line" (Extended Data Table 2, p38): I ...
Jim421616's user avatar
  • 2,558
9 votes
1 answer
314 views

Was the discovery of six exoplanets around one star as "easy" as counting six peaks in the FT?

The phys.org article Scientists make huge dataset of nearby stars available to public describes the release of a publicly accessible database of Echelle radial velocity measurements; The LCES HIRES/...
uhoh's user avatar
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8 votes
1 answer
847 views

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 ...
Leos Ondra's user avatar
  • 1,074
8 votes
1 answer
512 views

Why is $H_\delta$ prominent in type A stars?

I understand factually that H$\delta$ lines are most prominent in type A stars and less so in more extreme types of stars on the H-R diagram. However I was wondering the reason for why they are not ...
QuantumPanda's user avatar
8 votes
2 answers
797 views

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 ...
uhoh's user avatar
  • 30.6k
8 votes
2 answers
238 views

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 ...
DJL's user avatar
  • 181
8 votes
1 answer
195 views

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 ...
HDE 226868's user avatar
  • 36.6k
8 votes
2 answers
631 views

How well can we in principle determine $T_{\textrm{eff}}$ of a star?

This is a question about the basics of astronomy, which I have never happened to see a good discussion for. It is about how well would we be able to measure effective temperature of a star, if we had ...
Alexey Bobrick's user avatar
7 votes
4 answers
5k views

Why doesn't the Sun produce an emission spectrum?

I have read that the reason why the Sun produces an absorption spectrum is because the temperature drops as you go away from the center, such that as the various layers of the atmosphere of the sun ...
Physics2718's user avatar
7 votes
3 answers
2k views

Solar visible light spectrum

So the visible light from stars can be used to identify the elements in that star by looking at the spectral emission lines and comparing those lines to emission lines of various elements (and their ...
Milwrdfan's user avatar
  • 381
7 votes
2 answers
501 views

Does the expansion and contraction of a variable star affect the measured radial velocity?

I've measured the heliocentric radial velocity of Beta Cephei using the doppler shift of the helium lines, I corrected for earth's motion using the doppler shift of the oxygen in the atmosphere. I ...
Jackson's user avatar
  • 235
7 votes
1 answer
1k views

Star surface temperature?

I'm already familiar with using the difference in B and V magnitudes to calculate temperature, but Wikipedia (trustworthy source, I know) mentions that U-B, V-R, and R-I are also used depending on ...
Kazon's user avatar
  • 587
7 votes
1 answer
163 views

What forces expelled these huge clouds, then blocked further progress, yet allowed it to maintain its threads?

From Wikipedia and NASA: Caption: NASA: S74-15583 (July 1973) --- A huge solar eruption can be seen in this Spectroheliogram obtained during the Skylab 3 mission by the Extreme Ultraviolet ...
uhoh's user avatar
  • 30.6k
7 votes
1 answer
142 views

Have we detected spectra of exotic atoms in stars?

I was reading this wikipedia article on positronium (a type of exotic atom) and noticed it mentioned that positronium has a spectra (of course). So naturally this makes me wonder, have we looked at ...
Sidharth Ghoshal's user avatar
7 votes
1 answer
6k 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 ...
quantumflash's user avatar
7 votes
1 answer
459 views

Strong orange line in wood fire spectrum?

I just built a DIY spectroscope using a CD and after making some tests, I noticed a really strong emission line located in the orange-yellowish zone of the fire spectrum (specifically, burning wood). ...
Jotarata's user avatar
7 votes
1 answer
337 views

How do amateur astronomers do stellar spectroscopy?

This question consists of 2 parts: How can amateur astronomers measure the spectrum of stars? In addition to diffraction gratings, what equipment do they use (like telescopes, and the focal length ...
user avatar
7 votes
1 answer
118 views

What effect does stellar granulation to have on a chemical analysis of a star's spectrum?

The spectrum from stellar granules will obviously be for hotter gas, while the spectrum from the lanes between them will be for cooler gas. Does this "average out" so that an average ...
Jay D's user avatar
  • 323
7 votes
1 answer
135 views

Is it conceivable that the presence of chlorophyll (or similar) could be distinguishable from other chemicals on an exoplanet?

If an Earth-like exoplanet had a sufficiently extensive plant biosphere (i.e large forests, aquatic algal mats etc), is it at all conceivable that scientists could spectroscopically detect the ...
user avatar
7 votes
1 answer
327 views

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 ...
uhoh's user avatar
  • 30.6k
7 votes
1 answer
226 views

What are realistic and unrealistic values for the high energy gamma ray spectral indices of pulsar wind nebulae?

This summer, I was working on a project fitting very high energy gamma ray spectra of the Crab Nebula, a pulsar wind nebula. At energies about $\sim$1 TeV, a simple power law suffices, i.e. $\phi(E)\...
HDE 226868's user avatar
  • 36.6k
6 votes
3 answers
1k views

How accurate is astronomical spectroscopy?

We all now that green is a mixture of blue and yellow, and that purple is a mixture of red and blue. In astronomical spectroscopy the chemical composition of a planet’s atmosphere is determined, by ...
Constantthin's user avatar
6 votes
2 answers
1k views

Why does Earth have a dip in the CO2 absortion spectrum from 14 to 16 micron?

This paper shows that there is a dip in the CO2 absorption spectrum of Earth. In essence the trough of the absorption of CO2 for Earth is cut into two separate troughs instead of 1 large trough. Why ...
a.t.'s user avatar
  • 183
6 votes
2 answers
1k views

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 ...
Elena Greg's user avatar
6 votes
1 answer
803 views

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 ...
Yoav Zack's user avatar
  • 163
6 votes
1 answer
1k views

What is the temperature of the solar atmosphere (the corona) and how is it measured?

The temperature of the Sun's atmosphere, also referred to as the solar corona, is known to be hot even hotter than the Sun's surface. What is its temperature and how is it measured? How does it ...
ehsteve's user avatar
  • 1,154
6 votes
1 answer
391 views

Natural line width from absorption lines

Emission lines have a certain natural width. Due to the uncertainty principle systems that spontaneously decay or produce radiation have a fundamental energy blur, and their radiation has a ...
trynerror's user avatar
  • 849
6 votes
1 answer
520 views

What is a pupil slicer, and how does it work with anamorphic optics in VLT's ESPRESSO Echelle spectrograph?

This excellent answer points to ESPRESSO, - Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations. From there I looked at the Instrument Description and Performance page. ...
uhoh's user avatar
  • 30.6k
6 votes
2 answers
2k views

What does the ']' in the spectral line "CIII] 1909 Å" mean?

The above emission line, as I understand, is a useful probe of early star-forming galaxies. However, I do not understand what the ']' to the right of the 'CIII' means. I could not find any online ...
H3007's user avatar
  • 63
6 votes
1 answer
121 views

How do astronomical spectrometers measure spectra from single stars separately, without contamination from all of the nearby stars?

I am currently looking into light spectrometers, and I noticed that the ones I found had a similar problem; when the light reaches the spectrometer, it mixes giving a broad range of light wavelengths. ...
Aakarsh Tathachar's user avatar
6 votes
1 answer
93 views

Where can I find datasets for all confirmed exoplanets, terrestrial exoplanets, and Super-Earth exoplanets?

The NASA Exoplanet Archive has a Planetary Systems dataset offers celestial mechanical data for 5,197 confirmed exoplanets. The Exoplanets Catalog classifies these exoplanets as terrestrial, super-...
Tom Lever's user avatar
  • 191
6 votes
0 answers
190 views

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 ...
ProfRob's user avatar
  • 155k
6 votes
0 answers
119 views

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 ...
Lakey's user avatar
  • 161
5 votes
2 answers
454 views

Why would someone choose a lower resolution grating over a higher one when performing spectroscopy?

The higher spectral resolution grating would reduce the spectral range. Besides that, would a higher resolution grating reduce the signal per pixel? I thought I heard someone mentioned this to me a ...
Astroturf's user avatar
  • 1,111
5 votes
1 answer
169 views

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$...
Carlos Vázquez Monzón's user avatar
5 votes
2 answers
779 views

How to find the resolution of a spectrum?

I have been tasked to find the spectral resolution of some synthetic spectra (wavelength in Angstroms vs. flux) of different stars and degrade them to the resolution of observed spectra. But I am not ...
SaptarshiS's user avatar
5 votes
1 answer
468 views

Why are the wings of many strong lines, including hydrogen lines and most metal lines, stronger in Dwarfs than in Supergiants?

What is the reason? Is it because Dwarfs have higher surface gravity (log g), in turn related to pressure, than Supergiants so there is more contribution from van der Waals and Stark broadening?
Jay D's user avatar
  • 323

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