Unknown Spectral Lines in Sunlight

[EdEarl]

There are some 29,000 spectral lines in Sunlight, with 15% unidentified. What hypothesis are there to explain them? The spectral lines of all the elements are known, except perhaps for some of the ones with extremely short half-lives. Is it possible that states of matter exist in the sun that we don't know about, which create the unidentified spectral lines? Is it possible that dark matter is involved?

Edited March 19, 2015 by EdEarl

[swansont]

The spectral lines of all the elements are known

Are they? For all of the ionization states? And what about molecular states that are already ionized as they form?

[EdEarl]

Are they? For all of the ionization states? And what about molecular states that are already ionized as they form?

"For all of the ionization states?" ... IDK

For "molecular states ..." The photosphere is about 6000K, and the interior of the sun is millions K; can a molecule exist at such temperatures?

[imatfaal]

Ed - are you talking about emission lines or absorption lines?

 

In the Absorption Lines (first measured and classified by Fraunhofer and named after him) the line at 6867 angstroms is Atmostpheric Oxygen. You can see from this example that not all absorption lines occur due to interactions within the sun itself.

[swansont]

"For all of the ionization states?" ... IDK

For "molecular states ..." The photosphere is about 6000K, and the interior of the sun is millions K; can a molecule exist at such temperatures?

Not for long, but you could get a photon out when they temporarily bonded. Temperature matters but so does density — the important factor is the time, which will be related to the mean free path and speed.

[EdEarl]

I made a mistake (corrected now) in the OP. Not 15,000 unidentified spectral lines, but 15% of 29,000.

 

Ed - are you talking about emission lines or absorption lines?

 

In the Absorption Lines (first measured and classified by Fraunhofer and named after him) the line at 6867 angstroms is Atmostpheric Oxygen. You can see from this example that not all absorption lines occur due to interactions within the sun itself.

My source is a TED Talk by Garik Israelian, titled: How spectroscopy could reveal alien life, starting about 4:35 mins. As I understand his statement, they are emission lines.

[imatfaal]

I think he is talking about absorption lines

 

How we get spectra? I'm sure most of you know from school physics that it's basically splitting a white light into colors. And if you have a liquid hot mass, it will produce something which we call a continuous spectrum. A hot gas is producing emission lines only, no continuum. And if you place a cool gas in front of a hot source, you will see certain patterns which we call absorption lines. Which is used actually to identify chemical elements in a cool matter, which is absorbing exactly at those frequencies.

 

from the transctipt at 3:08

[Sensei]

If you have spectral tube with ionized gas inside f.e. Hydrogen, and also turn on magnetic field around them, spectral lines will start diverging. Shift will depend on magnetic field strength.

You won't have anymore 410 nm, 434 nm, 486 nm, 656 nm etc. but +- shift.

 

[EdEarl]

If you have spectral tube with ionized gas inside f.e. Hydrogen, and also turn on magnetic field around them, spectral lines will start diverging. Shift will depend on magnetic field strength.

You won't have anymore 410 nm, 434 nm, 486 nm, 656 nm etc. but +- shift.

 

Wouldn't astronomers who read spectrograms be aware of this phenomenon; thus, these perturbations would not account for unknowns? Or, does the Sun produce such variable magnetic fields to prevent such identification?

[swansont]

If you have spectral tube with ionized gas inside f.e. Hydrogen, and also turn on magnetic field around them, spectral lines will start diverging. Shift will depend on magnetic field strength.

You won't have anymore 410 nm, 434 nm, 486 nm, 656 nm etc. but +- shift.

 

 

 

That Doppler width of the transition at room temperature is several GHz, and gets larger as you get hotter. It would be hard to see Zeeman lines or shifts at the normal solar field strengths. In the visible, a 1 GHz shift is smaller than 0.01 nm. Possible in sunspot areas.

 

strongest field on the sun will be in sunspots, at a fraction of a Tesla, with the normal field being ~1k times smaller

http://zebu.uoregon.edu/~imamura/122/lecture-6/solar_activity_cycle.html

[Sensei]

AFAIK stars magnetic field strength is measured using Zeeman effect

http://en.wikipedia.org/wiki/Stellar_magnetic_field

 

Zeeman–Doppler imaging

http://en.wikipedia.org/wiki/Zeeman%E2%80%93Doppler_imaging

[swansont]

AFAIK stars magnetic field strength is measured using Zeeman effect

http://en.wikipedia.org/wiki/Stellar_magnetic_field

 

Zeeman–Doppler imaging

http://en.wikipedia.org/wiki/Zeeman%E2%80%93Doppler_imaging

 

 

From source 3 in the first link

 

"To make matters worse, one can only work with the integrated light from the whole star. For Zeeman broadening, this means that other forms of spectral line broadening are competing effects. Not only is there thermal and turbulent broadening, but the rotation of the star can produce Doppler broadening (one side of the star is coming toward the observer and the other side receding). Typically the magnetic broadening is comparable to, or swamped by, these other forms of broadening."

 

The second link is talking about detecting the polarization of the light from the Zeeman effect, not the shift, and works with stars that have fast rotations. So, while useful for some stars, not useful for the sun.

[MonDie]

The TED talk. see 4:30

 

[snip]
Is it possible that states of matter exist in the sun that we don't know about, which create the unidentified spectral lines? Is it possible that dark matter is involved?

Why do you think they require an extraordinary explanation? Maybe they're just ambiguous.

Edited March 19, 2015 by MonDie

[John Cuthber]

"There are some 29,000 spectral lines in Sunlight, with 15% unidentified. What hypothesis are there to explain them? "

Nobody bothered to index the last 15% or so seems like a plausible hypothesis to me.

There's also the problem that some of those lines might be rather weak (Take a gas cell a thousand miles long...).

And they might only occur at high temperatures.

(Heat the cell to 5000 degrees).

Edited March 19, 2015 by John Cuthber

[EdEarl]

Electric arcs can get as hot as 35,000F (19,400C); thus, I'd think the spectral lines of elements would be well known, at least to that temperature, which is hotter than the surface of the Sun.

[swansont]

Electric arcs can get as hot as 35,000F (19,400C); thus, I'd think the spectral lines of elements would be well known, at least to that temperature, which is hotter than the surface of the Sun.

 

I'm not seeing the connection. Measuring spectra is a tad more complicated than generating an electric arc.

[EdEarl]

 

I'm not seeing the connection. Measuring spectra is a tad more complicated than generating an electric arc.

It is a heat source to ionize materials. According to Wikipedia:

 

Modern implementations of atomic spectroscopy for studying visible and ultraviolet transitions include flame emission spectroscopy, inductively coupled plasma atomic emission spectroscopy, glow discharge spectroscopy, microwave induced plasma spectroscopy, and spark or arc emission spectroscopy. Techniques for studying x-ray spectra include X-ray spectroscopy and X-ray fluorescence (XRF).

Emphasis mine.

[swansont]

It is a technique, not the technique. That it exists doesn't mean it works for all elements.

[John Cuthber]

Electric arcs can get as hot as 35,000F (19,400C); thus, I'd think the spectral lines of elements would be well known, at least to that temperature, which is hotter than the surface of the Sun.

Those are emission lines. The lines from the Sun are (generally) absorption lines.

 

The potential for overlaps of the lines also makes it impossible to index some of them.