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Questions about the measurement of light waves whereby the wavelength is classified by its position in the electromagnetic spectrum.

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0answers
36 views

Why does D4000 affect stellar age?

From my understanding D4000 is a ratio between the 'flux densities between 4050 and 4250 Angstroms and that between 3750 and 3950 Angstrom', from Poggianti et al (1997). However I do not understand ...
7
votes
1answer
356 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 ...
5
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2answers
70 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 ...
1
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1answer
111 views

At what speed does something have to travel away from us for it to red shift enough that it becomes invisible to the human eye?

Are there stars, galaxies etc that we cannot see because they are traveling too fast and their spectrum is shifted below our visible range? From what I understand, red shift is caused by stars and ...
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1answer
46 views

Redshifting restframe SED

I have a template spectral energy distribution (SED) at z=0. I want to shift the template SED to an arbitrary redshift (z>0), how to do this in python?
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2answers
33 views

How is IR spectroscopy used to determine the composition of asteroids?

I am trying to understand how spectrometers or spectroscopy can be used to calculate the surface composition of asteroids for the purposes of asteroid mining.
2
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2answers
79 views

absorption line from the chromosphere

If I understand correctly, the H-alpha and Ca II K lines are absorption lines of the sun and allow to see the chromosphere. Following the Kirchhoff-Bunsen law, an absorption line is produced by a gas ...
2
votes
1answer
66 views

Determining line ratios in planetary nebula

I know that the line strength ratio tells us how hot the electron plasma in a nebula is, and also give information about the electron densities in the nebula. But how do you compute the line ratios? ...
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1answer
39 views

Where can I find a database of elemental spectra? [closed]

I know that spectroscopy can be used to analyze the light of stars to determine the elements causing their emissions in the visible spectrum, but this requires knowing the emission spectra of the ...
0
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1answer
35 views

What spectral feature was used to confirm that S0-2 is “single and available”? What is Brγ?

The Phys.org article Astronomers discover S0-2 star is single and ready for big Einstein test describes the results of a careful analysis of radial velocity measurements of the star S0-2, which orbits ...
1
vote
1answer
33 views

How does an Echelle spectrograph put such a long, high resolution spectrum into a square-ish format?

In order to obtain a very high resolution spectrum to resolve closely spaced lines, or to measure doppler shits, spectrographs are operated with very high dispersion. But photographic plates and CCDs ...
5
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0answers
60 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 ...
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1answer
23 views

Stellar electromagnetic signatures

By using only the electromagnetic signature of a star, could a star be distinguished with reliable accuracy from any other star? To elaborate a little, say we have a collection of about 200,000 stars. ...
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0answers
29 views

What could the rate of spread of the red parts of the CMB data physically imply ?

Let us take a CMB map just for reference. I have read that over time these red patches (parts which have a higher temperature) are spreading with some particular rate, my question is why is it ...
2
votes
1answer
34 views

How are the ESPRESSO Echelle spectrograph's calibration “lines” produced?

The CBC News Technology and Science Q&A This ESPRESSO machine doesn't make coffee but scans the skies for habitable planets includes a nice description of ESPRESSO (Echelle SPectrograph for Rocky ...
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0answers
73 views

How does the ESPRESSO Echelle spectrograph fold the spectrum so nicely?

The CBC News Technology and Science Q&A This ESPRESSO machine doesn't make coffee but scans the skies for habitable planets includes a nice description of ESPRESSO (Echelle SPectrograph for Rocky ...
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0answers
38 views

Spectroscopy of Exoplanets [closed]

How is accurate spectral analysis of a planets atmosphere achieved, bearing in mind that its host star's resultant light emission is not a full spectrum?
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0answers
46 views

Where can I get radial velocity data on HDE 226868/Cygnus X-1 and A0620-00?

I want to plot the radical velocity curve of HDE 226868/Cygnus X-1 or A0620-00 from REAL data. Where could I get the full data from spectroscopy and photometry?
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0answers
67 views

About photometry and spectroscopy of eclipsing binaries

Suppose an eclipsing binary system whose orbital plane is inclined i=90º. What are the optimal conditions to measure the light curve? Would it be easy to measure radial velocities?
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0answers
46 views

Source for Identification of Balmer Hydrogen Absorption Lines

I'm working on an assignment, where I have to classify stars using the raw data of the telescope. I'm now trying to calibrate the pixel to armstrong ratio, and for that I need to identify the ...
4
votes
3answers
265 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 ...
1
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0answers
78 views

How long would it take to collect a certain amount of photons? [closed]

So, I've received this question to solve, it's not a very advanced one, though advanced enough to cause headaches. The situation is as follows: Say, you are observing with a telescope with an ...
3
votes
1answer
97 views

Integral Field Spectroscopy vs Fabry-Perot Interferometry

Why are Fabry-Perot Interferometers (FPIs) and Fourier Transform Spectrographs (FTSs less common than Integral Field Spectrographs (IFS) nowadays? My understanding is that: With FPIs and FTSs you ...
6
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1answer
88 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 ...
1
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1answer
66 views

How do elements with only one shell emit light? [closed]

Electrons move to higher energy levels and drop back (electron migration). When they drop levels, photons are emitted and the wavelength/frequency emitted is based on how many levels are dropped. My ...
0
votes
1answer
424 views

How to convert theoretical template spectrum from luminosity density to flux density units?

I'm working with galaxy spectral templates (e.g., Bruzual & Charlot 2003) which seem to always come with y-axis units of $L_{\odot}$/A and x-axis units of Angstroms. Thus the y-axis is a ...
2
votes
4answers
752 views

Can some stars not emit any energy in the visible spectrum?

Stars convert mass into energy. Even converting the slightest mass into energy is immense because the speed of light is so great and $E = mc^2$. This means that stars have to emit large amounts of ...
9
votes
1answer
147 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/...
3
votes
1answer
147 views

Why do different instrumental filters use different magnitude systems (Vega vs AB)?

Suppose I wanted to construct the spectral energy distribution (SED) of an object. Further suppose I observe this object through the 9 broad-band filters using the Subaru Suprimecam (just for an ...
0
votes
1answer
43 views

How does glass affect taking solar spectra?

In this case I'm using a CCD camera mounted telescope pointed at the clouds to take solar spectra and was wondering how the telescope being pointed at the clouds through a double gazing (two layer) ...
2
votes
2answers
698 views

Are blue and red shift visible?

When looking into the sky at night using my bare eyes, I see that stars appear in different colors. From my understanding this is caused by different chemical compositions of those stars which show up ...
3
votes
1answer
65 views

wavelength-based IFU data cubes VS velocity-based IFU data cubes

I have 2 simulated IFU data cubes of the same observation, let's say A and B. The 3rd dimension of cube A is in wavelengths. In order to create cube B I just rebinned cube A in log-wavelengths and ...
4
votes
1answer
117 views

Have we Observed Continuum Emission from Neutron Stars?

Have we detected continuum optical emission from any rotating neutron stars that do not have an accretion disk dominating the light? I ask because I know we have observed Doppler broadening of ...
1
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1answer
264 views

What's the differences between one-dimensional spectrum and two-dimensional spectrum?

mostly, we use the one-dimensional spectrum. But sometimes we use two-dimensional spectrum, what's the differences between them?
1
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1answer
37 views

What's the slit and slot on EIS(EUV Imaging Spectrometer) instrument of Hinode?

There are two slits and two slots on EIS, are they just four types of grating?
2
votes
3answers
333 views

How to calculate the S/N of IFU or long-slit galaxy observations

I would like to calculate the Signal-to-Noise ratio (SNR) of long-slit or integral field unit (IFU) observations of H$\alpha$ emission. I can calculate the SNR or each individual spectrum, just fine. ...
1
vote
1answer
130 views

What (actually) does “peculiar periodic spectral modulations” refer to in this preprint?

I saw this ArXiv preprint after reading about it in the popular media. I can not even understand the beginning of the introduction (much less the whole paper): INTRODUCTION A Fourier ...
8
votes
3answers
540 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 ...
1
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0answers
55 views

Can all astronomical signals be considered Gaussian noise?

While studying the techniques astronomers use to mitigate radio frequency interference (RFI) I found it's often assumed that astronomical signals are (band-limited) Gaussian noise. Is this a ...
3
votes
2answers
233 views

Signal-to-noise in inverse angstrom for spectroscopy?

In a paper I came across the description of the signal-to-noise ratio (SNR) for observations with a spectograph. This was reported as $10\:1/\mathring{A}$. I am rather new to spectroscopy, so could ...
3
votes
1answer
839 views

How deep is the “A” Fraunhofer line in the solar spectrum? Is it from the Sun's or Earth's atmosphere?

Question: Where can I see - or even download - a fairly high resolution (~0.1 nm) solar spectrum at zero air mass - in other words from space without absorption and other features from the Earth's ...
4
votes
1answer
444 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 ...
5
votes
1answer
77 views

Is remote measurement of isotope ratios possible, or must a sample be aquired

Is it possible to measure to measure isotopic abundance of remote astronomical objects - ie measurement without having a sample to feed into a mass spectrometer? Do different isotopes show any ...
0
votes
1answer
109 views

Extraction of error spectrum in Sloan Digital Sky Survey

I need to know does SDSS spectrum contains error spectrum as well? http://www.sdss.org/dr12/spectro/spectro_basics/#AbouttheSpectra The above link says, further HDU's contain error spectrum and than ...
0
votes
1answer
346 views

Converting ångström spectral dimension to galaxy speed (km/s)

I have a spectral cube (in FITS format) whose spectral dimension is in ångströms. The sampling along the spectral dimension is 0.28A (CDELT=0.28). The observation in the cube is Ha emission of a ...
0
votes
1answer
91 views

How do astronomers distinguish the spectral lines?

As a black body a star emits a continuous spectrum of light and other radiation. I've learned they are capable of knowing of what elements the stars are made of because of the spectral lines. But how ...
3
votes
1answer
2k 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 ...
0
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1answer
510 views

How do I apply a velocity shift to a wavelength array with uniform logarithmic spacing?

Suppose I have a wavelength array for a spectrum in units of Angstroms. Suppose further that the wavelength has "uniform logarithmic spacing" such that if I just take the difference in Angstroms ...
1
vote
2answers
52 views

Which elements are an indication of habitable exoplanets?

Using spectroscopy the chemical composition of exoplanets atmosphere is determined. As a scientist, what spectral lines would you look for? Which elements are relevant in pursue of a second earth?
3
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0answers
628 views

What is meant by ionization states?

I am going through the theory of saha equation but I am not able to understand the concept of ionisation state? What are ionization states actually?