Vega is a nearby star that has one of its poles facing Earth. A number of spectra for this star have been recorded, with at least one in the public domain.
This laboratory is an activity for you to analyze the spectrum of Vega, or any star of your choice that you can find a spectrum for. While it is part of the astronomy course principles of radiation astronomy, it is also independent.
Some suggested entities to consider are emission lines, continua, background, absorption, reflection, or protoplanetary disk.
More importantly, there are your choice of entities.
You may choose to define your primordial entities or not.
Usually, research follows someone else's ideas of how to do something. But, in this laboratory you can create these too.
Okay, this is an astronomy spectroscopy laboratory, but you may create what a spectrum is and its limits.
Yes, this laboratory is structured.
I will provide the example of Vega for analysis. The rest is up to you.
Questions, if any, are best placed on the discussion page.
You are free to create your own notation or use those available.
For creating an analysis of the spectrum of Vega, what would make an acceptable control group? Think about a control group to compare your spectral analysis or your process of creating such an analysis to.
At the top right of this resource is an instrumentally corrected full spectrum of the star Vega.
The second part of the laboratory is to produce or locate an annotated spectrum or set of spectra that indicate which lines come from what elements.
Each of the annotated spectra at right display portions of the spectrum at the top of this resource:
- the wavelength domain from 380.0 nm to 500.0 nm,
- the 500.0-600.0 nm domain,
- the 600.0-700.0 nm domain,
- the 700.0-800.0 nm domain,
- the 800.0-900.0 nm domain, and
- the 900.0-1020.0 nm domain.
Each of these images at right has various element lines labeled: calcium, hydrogen, iron, magnesium, nitrogen, oxygen, silicon, sodium, and titanium.
Molecular lines occur for H2O and O2 which are likely from Earth's atmosphere or the accretion disk around Vega.
The applicable astronomies are
- violet astronomy, blue astronomy, cyan astronomy, and green astronomy,
- green astronomy, yellow astronomy, and red astronomy,
- red astronomy and near infrared astronomy, and
- near infrared astronomy,
- near infrared astronomy, and
- near infrared astronomy.
The principal low atomic number elements of interest, whose lines need to be identified are
- fluorine, and
Identification of ionization state should be made where possible.
Element lines and wavelengths can be verified using these resources:
- Alexander Kramida, Yuri Ralchenko, and Joseph Reader (September 24, 2012). NIST Atomic Spectra Database, Version 5. 100 Bureau Drive, Gaithersburg, Maryland USA: National Institutes of Standards and Technology (NIST). Retrieved 2013-01-20.CS1 maint: Multiple names: authors list (link)
- Jean E. Sansonetti and W. C. Martin, and S. L. Young (December 9, 2011). Handbook of Basic Atomic Spectroscopic Data. 100 Bureau Drive, Gaithersburg, Maryland USA: Physical Measurement Laboratory, NIST. Retrieved 2013-01-24.
The element lines to look for and verify whether present or not are
- hydrogen, all high intensity lines detected and state properly labeled.
- helium, the two major lines at 388.86 and 706.519 nm are possible but may overlap the hydrogen line at 388.90 nm.
- lithium - no lines detected.
- beryllium - no lines detected.
- boron - two strong lines are possible, the 412.1933 nm as a shoulder on H I 410.17 nm line, while the other 448.705 nm overlaps the labeled 448.11 Mg II line.
- carbon, the line at 723.642 nm is possible but unlabeled.
- nitrogen, high intensity lines labeled, but the 868.028 N I is possible as an unlabeled shoulder.
- oxygen - the 777.42 nm O I may be mislabeled and should be 777.194 nm O I which is the stronger line.
- fluorine - the 685.603 nm F I line is possible.
- neon - not detected.
For the heavier elements:
- sodium - the two Na I lines are properly labeled.
- magnesium - all of the lines may be wrong and mislabeled.
- calcium - all high intensity lines present and labeled, the Ca K is a Ca II line.
- titanium - the Ti II line at 439.50 nm is properly labeled as are the others.
- silicon - lines are properly labeled.
- iron - all are labeled properly, because the 501.84 nm line is only Fe II, which differentiates Fe I lines from Fe II lines.
Title The element lines of the spectrum of Vega between 388.0 nm and 1020.0 nm.
A detailed spectrum of starlight from the star Vega was collected on July 4, 2002, using a commercially available spectrometer. The lines were indexed and labeled as to element and ionization state. This analysis is a subsequent examination of the spectrum for possible misidentification, improper ionization state, and potential red shift or blue shift.
Vega is a nearby optical spectral type A0V star at about 25 lyrs. Its polar effective temperature is near 10,000 K, while its equatorial effective temperature is 7,600 K. Vega is a known soft X-ray source. If an X-ray classification of stars is possible, the cloud that became Vega may have any composition initially. Any surface fusion ongoing above the photosphere may be expected to produce some lighter elements. An examination of its spectrum may indicate some of these light elements.
The full optical spectrum of Vega between 388.0 nm and 1020.0 nm should reveal the protostar cloud initial composition plus atmospheric fusion products. Its soft X-ray output suggests only lower energy fusion products, if any. Spectral components from about 380.0-500.0 nm, 500.0-600.0 nm, 600.0-700.0 nm, 700.0-800.0 nm, 800.0-900.0 nm, and 900.0-1020.0 nm were examined for proper and complete labeling of peaks.
All high intensity hydrogen lines were detected and together with ionization states properly labeled. Helium lines (two) may be present but overlap the hydrogen lines. No lithium or beryllium was detected. Boron lines may be mislabeled as magnesium lines. The carbon line at 732.642 nm is a possible detection but is unlabeled. The nitrogen high intensity lines are present and labeled, and 868.028 nm N I line is possible as an unlabeled shoulder. Oxygen is present as monatomic although the 777.42 nm O I line may be mislabeled and should be the 777.194 nm O I line which is stronger. The high intensity fluorine line at 685.603 nm F I is possible, appears to be present, but is unlabeled. Neon was not detected.
Of the heavier elements, the alkali and alkali-earth sodium and calcium were detected. The metals titanium and iron are properly labeled and the Fe II line 501.84 nm is present and allows the differentiation between Fe I and Fe II ionization states. Silicon lines are present and properly labeled.
No red shift of blue shift is apparent.
The over riding presence of hydrogen suggests that very little atmospheric surface fusion has taken place. This is supported by the possible presence of boron. The presence of carbon, nitrogen, oxygen, and likely fluorine suggests that subsequent lower energy fusion has been consuming, or may have consumed the helium, lithium, and beryllium. Without neon being detected it is likely that the heavier elements are dust and debris captured by Vega or present as dust in the initial cloud before it was energized.
Vega is an optical spectral type A0V star that appears to have very little ongoing atmospheric surface fusion. Its current spectrum suggests only that the original cloud has been energized and contained heavier elements. The high surface temperature suggests that any electron beam heating is primarily directed toward the photosphere. As Vega has a pole towards Earth that may also be in a coronal hole, assessment of its potential X-ray classification is difficult.
To assess your spectral analysis, including your justification, analysis and discussion, I will provide such an assessment of my example for comparison.
No evidence is presented for declaring that the magnesium labeled lines are likely boron except comparison with NIST computer generated lines matched with observations. More detailed examination of the lines present, including the possible missing helium may suggest a different evolution for Vega than the one presented. Evidence allowing a choice between alternative evolutions was not presented or discussed.
- The spectrum of Vega is influenced by its pole pointing toward Earth.
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