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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3
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1answer
52 views

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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Does the current “fainting” of Betelgeuse show any spectral trends that differ from it's normal variability?

The Astronomers Telegrams #13341 The Fainting of the Nearby Red Supergiant Betelgeuse and #13365 Updates on the “Fainting” of Betelgeuse (both in December 2019) discuss the importance of measuring ...
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1answer
29 views

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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40 views

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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1answer
46 views

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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51 views

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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40 views

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 ...
2
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1answer
54 views

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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701 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 ...
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45 views

What is an “Off Rowland-circle Telescope”?

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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1answer
66 views

How will microshutter arrays be used in the James Webb and future space telescopes?

Question: How will microshutter arrays be used in the James Webb and future space telescopes? Are they acting as a sort of moving pinhole or slit, or is the pattern more complicated, like a coded ...
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2answers
43 views

What does the opacity of a molecular transition mean?

In particular, what does it mean when a line (e.g, emission line in stellar wind) is optically thick or thin. I know what an optically think/thick medium is, but how does this concept compare to ...
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1answer
74 views

How spectrographs that measure radial velocities manage to translate variations in the stars' spectrum lines into the “speed” of the star?

Like ESPRESSO or CARMENES, for example. I just don't understand the process or the way these spectrographs manage to obtain the velocity of the "wobble" of the star (due to the presence of another ...
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1answer
70 views

Thermal Doppler broadening

How to plot Doppler profile corresponding to the spectral line? The spectral line was plotted from data: flux with respect to wavelenght and I know the temperature. These two function are Doppler ...
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1answer
60 views

How to convert $K_S$ magnitude to $M_K$

My question is how do I convert a magnitude $K_S$, from a system like 2MASS, to $M_K$, and what are the differences. A use of this $M_K$ can be seen on Delfosse et al. (2000) in the $\log(M/M\odot) - ...
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1answer
39 views

How to model and subtract nebular emission lines from stellar spectrum

I have optical stellar spectra from a star forming region with spatially varying nebular background. I want to subtract the nebular lines from the stellar spectra (which are varying in intensity from ...
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1answer
39 views

What equipment do I need to measure the spectrum of a star?

For an amateur astronomer, is it possible to measure the spectrum of a star? I can easily take a photo of a star just by putting a camera on one end of a telescope and over exposing it. But I would ...
4
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1answer
89 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)\...
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1answer
86 views

SDSS Image Download: Swarp returns all zeros

In the CASJOBS Server, I created the following query for galaxies(DR12) ...
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2answers
58 views

First spectroscopic detection of Uranus' rotation?

As an undergraduate exercise quite a while ago, we placed the equator of Jupiter's disk across the slit of a high resolution grating spectrometer and then measured the tilt of the resulting line in ...
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61 views

Does Nickel show up in spectra of Nova?

Does a nova, not a supernova, get hot enough that nickel is produced despite its formation by fusion being an endothermic reaction? If nickel is made, does it make it out of the star into the nebula? ...
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Relation between oscillator strengths $\log{gf}$ and the Einstein $A$-coefficient, rotational quantum number,

I'm analyzing the spectra of M dwarfs. Some authors characterize the lines with the oscillator strengths $\log{gf}$ while others follow different paths with the Einstein $A$-coefficient. I would like ...
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1answer
36 views

Where can I find a good solar irradiance chart for the infrared?

I'm trying to understand the results of the ExoMars Trace Gas Orbiter vs the Mars Express in terms of their abilities to find methane on the surface of Mars. The solution that I'm coming to is that it ...
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1answer
48 views

Examples of absorption lines for main sequence stars

Where might I find a detailed table or figure containing the absorption lines and their corresponding wavelengths for each type of main sequence star? I'm trying to get the chemical abundance of ...
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1answer
67 views

Exposure time for spectroscopy compared to photometry

For a report I'm writing, I'm interested in comparing the exposure time required for spectroscopy versus photometry for a given magnitude. I found the figures on pages 7 and 8 of this lecture ...
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864 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 ...
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what/how do we mean/derive statistical equilibrium equation of certain energy levels?

While reading the research paper "Excitation of the Fe XIII Spectrum in the Solar Corona" by D.R. Flower and G. Pineau des Forets in the summary I found the concept of statistical equilibrium equation ...
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1answer
101 views

Why a blue spot in some hubble images of NGC 4302?

In some images with coloring like in this one: There is a noticeably bluer region in the "bottom left" of the image, and the bottom part of the galaxy on the left. Being an inexperienced galaxy ...
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1answer
57 views

Extracting kinematics from stellar spectra. Why are template stellar spectra necessary?

I am trying to understand how to extract stellar velocity and velocity dispersion maps from spectral cubes, but with no success so far. To be more precise, I do not understand why people use stellar ...
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1answer
59 views

Reference: First spectrographic observations by Fraunhofer

In several books I find reported that the first scientist to perform spectrographic observations of celestial objects was Fraunhofer with the spectrographs he himself produced. I do not find though a ...
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121 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). ...
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42 views

How do you fit a model SED to an observed galaxy spectrum with photometric data?

I have a spectrum of a galaxy from HST data and SDSS data (resulting in a nearly continuous SED from the FUV~1000 Angstroms through infrared). I have created a model SED with the galaxy simulation ...
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1answer
152 views

How do we know that the mass ratio of hydrogen and helium in the sun is approximately 3:1?

From what I learnt, we can find what elements are in the sun by analysing spectrums since each elements has same emission spectrum, and when you look at the sun's spectrum, you can see absorption ...
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Correction to inverse square law for cosmology

While reading about the discovery of quasars and the spectroscopic analysis of 3C 273 in this paper by Maarten Schmidt, I came across the following quote: At these distances, corrections to ...
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2answers
286 views

How to estimate uncertainty of measurements of equivalent widths?

I'm measuring equivalent widths of absorption lines using a spectrum of a star. I make two or three measurements of each line by making reasonable gaussian fits of the line with IRAF's splot tool. ...
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1answer
78 views

Hubble Space Telescope (HST) observing modes

I have been reading some literature on using the HST to take spectra of exoplanet atmospheres when exoplanets transit in front of their stars. The literature mention two modes of observations, '...
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1answer
44 views

Delete key does not always work in IRAF's xgterm on Mac

Sometimes it does not let me delete text in an xgterm terminal and outputs ^H instead. Example: Run IRAF: xgterm -e cl It opens the xgterm, there I type: <...
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1answer
101 views

What is the dimensions of the smallest object detectable by an optical fiber from a specific distance?

Optical fibers are well-known to observe astronomical objects, say, galaxies, to generate massive spectroscopic surveys. The galaxies are often very far from the optical fibers of a telescope. However,...
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Doppler Spectroscopy - Finding mass of an exoplanet

An astronomer, T observed the spectrum of a distant star X. The spectral lines were observed to have tiny blueshifts and redshifts regularly with a period of 1.27 years. T concluded that the star is ...
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1answer
57 views

Spectra and star identification [duplicate]

Are stellar spectra unique enough that they could be used to identify particular stars? If so, has any attempt been made to use them for navigation or equipment alignment?
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1answer
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What might a CN filter be in the context of comet watching? Is it showing dust, or gas, or something else?

In this post on the website for the Comet Wirtanen Observing Campaign at wirtanen.astro.umd.edu, there's mention of a CN filter being used to observe the comet, and this cool GIF. What exactly is a ...
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Help understanding the false MRO observations of hydrated minerals on Mars

The Science News article An orbiter glitch may mean some signs of liquid water on Mars aren’t real begins: Some signs of water on Mars may have just dried up. Thanks to the way data from NASA’...
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1answer
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What was the “optical illusion” that led to erroneous metal concentrations in stellar atmospheres in the galactic center?

Articles summarizing a recent result about certain heavy element concentrations in stars near the galactic center all say that earlier reports about high levels in stellar atmospheres were the product ...
3
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1answer
164 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. ...
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67 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 ...
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1answer
380 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 ...
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2answers
256 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 ...
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1answer
283 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
199 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
124 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.