What is amateur spectroscopy capable of?

[sjastro]

First of all a hats off to doing some real science.
I have absolutely no idea of the capabilities of amateur spectroscopy.

I asked TerryB a question in another forum if cosmological redshift could be observed using amateur equipment.

What about other phenomena such as:

(1) Splitting and shifting of lines due to the Stark and Zeeman effects.
(2) Doppler broadening of lines due to rotation.
(3) The Lyman alpha forest for quasars (I imagine this would be a tough one.)
(4) Any other phenomena.

Regards

Steven

[Merlin66]

Quick answer:
1. No, not easily
2. Yes
3. No, not easily...
4. Yes

The research abilities for the amateur are limited by aperture and resolution.
The star analyser (with a camera attached) and a reasonable amateur telescope will allow you to:
- measure the temperature of a star
- identify some of the absorption lines in the atmosphere
- measure redshifts of distant quasars fairly accurately
- identify the type of a supernova (if its bright enough)

There's work being done on WR and Be Stars, Novae and SN. From a recent message from John S.-
- if star is in a binary (or a multiple) star system you can potentially get a spectra with the combined spectra of the two stars in it - and using the way the lines move in the spectra as they go round each other you can work out the orbital parameters of the stars in the system
- if the star has exoplanets going round it you can determine the number and orbital parameters of the exoplanets going round it
- even better if you capture the spectra when an exoplanet is in front of the star you can extract the spectra of the exoplanet by subtracting the spectra from the star when the exoplanet was not in front of it!
- if you know the type of star you are looking at you can use deviations of expected intensity in some of the Calcium lines (and others) to work out the sort of material that is between us and the star!
- the shapes of the lines can be used to determine details of the stellar winds in some stars - wind momentum, terminal wind velocity
- the wind momentum is directly related to the luminosity of the star - from this believe it or not we can now work out the distance to the star
- also the shapes of the lines will tell you if there is an inflow of material going into the star and if the star has a disk of material going round it.
- high precision spectroscopy allows you to do something called astroseismology - all stars pulsate - the lines in the spectra of the star move as the stars pulsate - capturing this data allows you to study the structure of the star potentially deep below the stellar atmosphere.

and there is lots more...
- you can use spectra to detect mass exchange between stars in a binary system (if the stars are close enough to each other that the mass flow from one star to another)
- for stars with disks of material going round them such as Be stars the shape of some of the spectral lines allow you to calculate the inclination of the disk to you
- you can use spectra to determine the inclination of the star to you. For instance for vega it has been shown that one of its poles is facing us
- as we see the sun as a disk you can take spectra of different parts of the disk of the sun and observe the structure of the sun at different depths in its atmosphere. The nearer you take spectra to the limb of the sun the higher up in the sun's atmosphere you observe
- a number of spectra of standard stars have been taken by the hubble and other space telescopes. If you then take spectra from earth you can compare the difference between that spectra and the space one to determine the elements and the amount of extinction that light has as it goes through our atmosphere
- detection of starspots in some stars using molecular Titanium Oxide bands formed in them

And there's more...............

[robin_astro]

Here is one, though it is a rather untypically bright special case
http://www.threehillsobservatory.co.uk/astro/spectra_22.htm

Lots of other applications including several Pro-Am studies on my website too (at low and high resolution)

Cheers
Robin
www.threehillsobservatory.co.uk

[pvelez]

Robin

Now there is a challenge for the spectroscopists. Thanks for this.

Pete

[sjastro]

Thanks for the very informative response Ken.



Spectroscopy has also found strong evidence for the existence of Black Holes in binary systems. In X-ray binaries where the matter is falling into a white dwarf or neutron star the x-ray spectra shows two distinct signatures. One is the x-ray emission from the collision of matter with itself (high temperature heating with the subsequent emission) , the other is the matter colliding into the dwarf or neutron star. In some binaries this latter emission is missing, indicating the collision is occurring inside the event horizon of a Black Hole and therefore cannot be observed.

Regards

Steven

[sjastro]

Very impressive work Robin.

Regards

Steven

[Merlin66]

Almost 90% of everything we know about the Universe has been revealed using spectroscopes!!! Not "pretty" pictures ;-)
Some of the possible "projects" mentioned, to get good SNR and data really require some large apertures (and large spectroscopes).
Back to the real world.....of amateur spectroscopy....
Even with modest telescopes >200mm and a slit spectroscope the amateur can make scientific contributions..just look at some of the work that the local guys like Bernard H. and Terry B. are doing...
There was an interesting article by a German amateur, Ernst Pollmann, which links the conventional photometric magnitude estimates and results in changing Ha strength (in terms of Equivalent Width) to achieve a better analysis of the gas/ dust ring dynamics around a Be star.....
Onwards and upwards.