Element responsible for emission?

If I recall right, for nebulae, red usually indicates Hydrogen emissions
and green OIII(?), like in the ring nebula.

What element is responsible for the blue emissions around the Pleiades
or, say, around rho Ophiuchi?

Thanks much in advance.
--
I. N. G. --- http://users.forthnet.gr/ath/jgal/

On Mon, 10 Jan 2005 19:43:32 +0200, Ioannis wrote:

If I recall right, for nebulae, red usually indicates Hydrogen emissions
and green OIII(?), like in the ring nebula.

What element is responsible for the blue emissions around the Pleiades
or, say, around rho Ophiuchi?

Thanks much in advance.

Generally when you see blue, you are seeing reflection nebulas, not emission
nebulas. The blue is the reflected light from one or more nearby hot stars.
While the stars are basically white, blue is preferentially scattered by gas and
dust (why is the sky blue...)

_________________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com

Chris L Peterson wrote:

On Mon, 10 Jan 2005 19:43:32 +0200, Ioannis wrote:


If I recall right, for nebulae, red usually indicates Hydrogen emissions
and green OIII(?), like in the ring nebula.

What element is responsible for the blue emissions around the Pleiades
or, say, around rho Ophiuchi?

Thanks much in advance.


Generally when you see blue, you are seeing reflection nebulas, not emission
nebulas. The blue is the reflected light from one or more nearby hot stars.
While the stars are basically white, blue is preferentially scattered by gas and
dust (why is the sky blue...)

You mean something like a sort of "Rayleigh scattering" in the nearby area?

If this is the case, doesn't this necessarily imply the existence of gas
in the vicinity of those stars?

Why then doesn't THIS gas emit radiation at all from being excited by
those stars? Or if it does, perhaps the scattering dominates the emission?

Thanks!

_______________________________________________

Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com


--
I. N. G. --- http://users.forthnet.gr/ath/jgal/

Ioannis wrote:
Chris L Peterson wrote:

On Mon, 10 Jan 2005 19:43:32 +0200, Ioannis
wrote:


If I recall right, for nebulae, red usually indicates Hydrogen
emissions and green OIII(?), like in the ring nebula.

What element is responsible for the blue emissions around the
Pleiades or, say, around rho Ophiuchi?

Thanks much in advance.



Generally when you see blue, you are seeing reflection nebulas, not
emission
nebulas. The blue is the reflected light from one or more nearby hot
stars.
While the stars are basically white, blue is preferentially scattered
by gas and
dust (why is the sky blue...)


You mean something like a sort of "Rayleigh scattering" in the nearby area?

If this is the case, doesn't this necessarily imply the existence of gas
in the vicinity of those stars?

Why then doesn't THIS gas emit radiation at all from being excited by
those stars? Or if it does, perhaps the scattering dominates the emission?

The scattering is from dust grains rather than gas.

Clear skies,
Greg

--
Greg Crinklaw
Astronomical Software Developer
Cloudcroft, New Mexico, USA (33N, 106W, 2700m)

SkyTools Software for the Observer:
http://www.skyhound.com/cs.html

Skyhound Observing Pages:
http://www.skyhound.com/sh/skyhound.html

To reply have a physician remove your spleen

For Macholtz, your post above, its called resonant flourescence:
the green cyanogen CN and diatomic carbon, C2.

dfg



Ioannis wrote:

If I recall right, for nebulae, red usually indicates Hydrogen emissions
and green OIII(?), like in the ring nebula.

What element is responsible for the blue emissions around the Pleiades
or, say, around rho Ophiuchi?

Thanks much in advance.
--
I. N. G. --- http://users.forthnet.gr/ath/jgal/