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0answers
16 views

Bright lines in a continuum spectrum

Dark lines in a continuum spectrum is common. But are there bright lines too? By the stimulated emission process, the light can also be amplified, right? In this case, we should get bright lines ...
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0answers
24 views

What would we not know without spectroscopy?

What do we depend on spectroscopy to know about in astrophysics? Or, without spectroscopy, what would remain unknown to us? I want to know how important it is. My wife is studying spectroscopy in ...
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0answers
6 views

Convert axis display in ds9

I have a fits file of an echellogram with the axes showing the pixel indices. However, I would like to convert my horizontal axis from pixel to wavelength given that I have a conversion formula for ...
3
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1answer
41 views

How do you estimate the error on the height/width of a Gaussian?

I'm trying to fit Gaussians to several lines in a spectrum that I have. Some of them overlap with one another, causing the fitting program that I'm using to not be able to give reasonable estimates ...
2
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1answer
33 views

What is an “arc” spectrum ?

I sometimes hear about astronomers using an arc spectrum to calibrate observations. For example a "He-Ar arc spectrum". What is an "arc" in this context? I assume it's nothing got to do with angles ...
3
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1answer
30 views

Why do spectroscopic binaries have approximate circular orbits?

So for an assignment I have to answer the question what I can conclude concerning the shape of the orbit, knowing that it is both an eclipsing and spectroscopic binary. Now, I think the answer I ...
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1answer
44 views

How can I determine line luminosities from equivalent width measurements?

I have a set of equivalent width measurements for different emission lines. How can I use them in order to determine the corresponding line luminosities?
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0answers
29 views

How to use spectral profiles to determine luminosity class?

I know the luminosity classes are: Ia-0 ( Hypergiants ), Ia ( bright supergiants ), ... , VII ( white dwarf ). I also have learned that you can use the presence of absorption lines ( ie. use spectral ...
2
votes
1answer
40 views

How to determine atomic number density of an element in a star based on equivalent width measurements

Given an equivalent width measurement $W$ of a spectral line of element $X$ and the effective temperature $T_{eff}$ of a star, how can you determine the atomic number density of $X$ in that star? ...
3
votes
1answer
46 views

Gaia: What is the difference between CCDs used for astrometry, photometry, and spectroscopy?

My knowledge of CCDs is that these are sensors which collect photoelectrons. That's about it. What is a difference between CCDs used for astrometry, spectroscopy, and photometry? As an example, each ...
5
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1answer
121 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 ...
1
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1answer
54 views

How to specify SM libraries for MOOG

I am running MOOG on OS X Yosemite and with $MOOG running the abfind driver I can force fit elemental abundances with an appropriate input line list and model ...
1
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1answer
51 views

Why do we observe spectral lines of specific energy?

The basis of my confusion is that atomic orbitals, even when described accurately by quantum numbers, have definite energies, meaning they represent energy eigenstates of the wave function. They're ...
2
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1answer
53 views

Why is $g$ tied to the oscillator strength $f$ in $\log{gf}_{\odot}$

The $\log{gf}$ value of an element in a star, where $f$ is the oscillator strength, or probability of transition in an atom, is a scientifically pursued quantity with relation to the model atmosphere ...
2
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1answer
101 views

How to run MOOG on OS X Yosemite

By what process can a user running the latest version of OS X Yosemite execute MOOG with $MOOG in bash? Due to the removal of 32bit libraries in OS X 10.7+, the ...
2
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0answers
21 views

Halpha velocity fields of spirals falling into a cluster

What kind of impact would you expect ram pressure stripping / tidal interactions / harassment / interactions with the cluster potential (etc!) to have on the h-alpha velocity fields of infalling ...
0
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1answer
47 views

Can stars be observed from space by x-rays, near infrared and radio wavelengths? [closed]

I have a doubt. Can stars be observed from space by x-rays, near infrared and radio wavelengths?
-1
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1answer
78 views

How are molecules detected in space?

Recently the sugar glycoaldehyde was detected in a star system 400 light years from Earth. How exactly are molecules detected in space? I am aware that spectroscopy is used to detect them, but I don't ...
5
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1answer
87 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 ...
2
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1answer
26 views

Can spectroscopes identify minerals?

Could a spectrometer on a probe or space telescope identify minerals, not only elements and molecules, from the spectral lines? Is there any technology for identifying minerals remotely?
2
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1answer
40 views

Any cheap (<100 euro) tools for observing the lines in solar spectrum?

I am now reading the book ''The story of Helium and the Birth of Astrophysics''. I really want to observe the lines (dark or bright) in the solar spectrum. Any easily available tools for an amateur? ...
2
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1answer
105 views

Choosing a diffraction grating

I am interested in doing some solar spectroscopy on my own for fun. How do I go about choosing the appropriate diffraction grating?
2
votes
1answer
724 views

How do I calculate the velocity dispersion of a galaxy given an integral field spectrograph?

I couldn't find on the web how to get the velocity dispersion and velocity maps of galaxies from the 3D data cube that I get from the integral field spectrograph.
3
votes
2answers
920 views

How to measure distances to stars by means of spectroscopic parallaxes?

How to measure distances to stars by means of spectroscopic parallaxes on practice? What is the accuracy of measuring distances using this method compared with distances based on HIPPARCOS ...
11
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3answers
453 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 ...
7
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1answer
2k 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 ...
7
votes
2answers
190 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 ...