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Starforming nebula looks different at different wavelenghts
Posted: Sun Mar 09, 2014 7:13 am
by Ann
In the
Recent Submissions thread, there was
a fascinating Herschel image of NGC 7538, one of those rare sites of truly high-mass star formation. The Herschel telescope detects far infrared light, and the picture is a composite of exposures through filters of 70, 160 and 250 microns.
NGC 7538 has also been photographed by the Spitzer Space Telescope in mid infrared light at wavelenghts 3.6 and 4.5 microns. This makes the nebula and its dust-enshrouded stars look quite different.
Finally, take a look at
this RGB/Ha/OIII picture of NGC 7538 by Emil Ivanov. This image highlights the presence of OIII emission caused by the young high-mass stars.
Certainly a nebula containing high-mass star formation must look different at different wavelengths, but I think that NGC 7538 is a particularly striking example.
Ann
Re: Starforming nebula looks different at different waveleng
Posted: Sun Mar 09, 2014 2:35 pm
by Chris Peterson
Ann wrote:Certainly a nebula containing high-mass star formation must look different at different wavelengths, but I think that NGC 7538 is a particularly striking example.
What object, astronomical or otherwise, isn't going to look different at different wavelengths?
Re: Starforming nebula looks different at different waveleng
Posted: Sun Mar 09, 2014 3:49 pm
by Ann
Chris Peterson wrote:Ann wrote:Certainly a nebula containing high-mass star formation must look different at different wavelengths, but I think that NGC 7538 is a particularly striking example.
What object, astronomical or otherwise, isn't going to look different at different wavelengths?
Point taken, certainly.
I just thought that the three different pictures I found were so interesting when I compared them.
Ann
Re: Starforming nebula looks different at different waveleng
Posted: Sun Mar 09, 2014 4:11 pm
by geckzilla
Chris Peterson wrote:Ann wrote:Certainly a nebula containing high-mass star formation must look different at different wavelengths, but I think that NGC 7538 is a particularly striking example.
What object, astronomical or otherwise, isn't going to look different at different wavelengths?
I have no idea how such an object could be engineered and be bright enough for someone to see at least across galactic distances but if it were possible it would be a cool beacon to let anyone else know you're out there. No mathematical messaging or interpretation required!
Re: Starforming nebula looks different at different waveleng
Posted: Sun Mar 09, 2014 4:28 pm
by Chris Peterson
Ann wrote:Point taken, certainly.
I just thought that the three different pictures I found were so interesting when I compared them.
Agreed.
Re: Starforming nebula looks different at different waveleng
Posted: Sun Mar 09, 2014 4:30 pm
by Chris Peterson
geckzilla wrote:I have no idea how such an object could be engineered and be bright enough for someone to see at least across galactic distances but if it were possible it would be a cool beacon to let anyone else know you're out there. No mathematical messaging or interpretation required!
It should be possible in principle to engineer a light source that had a flat intensity or energy spectrum across some particular range. I agree that if we observed such a thing, it would be hard to recognize it as anything other than artificial.
Re: Starforming nebula looks different at different waveleng
Posted: Sun Mar 09, 2014 6:12 pm
by neufer
Chris Peterson wrote:geckzilla wrote:
I have no idea how such an object could be engineered and be bright enough for someone to see at least across galactic distances but if it were possible it would be a cool beacon to let anyone else know you're out there. No mathematical messaging or interpretation required!
It should be possible in principle to engineer a light source that had a flat intensity or energy spectrum across some particular range.
I agree that if we observed such a thing, it would be hard to recognize it as anything other than artificial.
http://en.wikipedia.org/wiki/White_noise wrote:
<<White noise is a random signal with a constant power spectral density. White noise draws its name from white light, although light that appears white generally does not have a flat spectral power density over the visible band.
An infinite-bandwidth white noise signal is a purely theoretical construction. The bandwidth of white noise is limited in practice by the mechanism of noise generation, by the transmission medium and by finite observation capabilities. In music and acoustics, the term "white noise" may be used for any signal that has a hissing sound. White noise is sometimes used in the metaphoric sense of "
random talk without meaningful contents".>>
