timokarhula
12-11-2010, 02:01 AM
I think this forum is perfect for my question. I'm an amateur astronomer from Sweden who regularly makes a trip to Western Australia, because I have an apartment in Geraldton after my late father. Last year, in November - December, I made a trip 130 kms to the inland where light pollution is unknown. :D My naked eye limiting magnitude was 7.9 and the SQM-L meters showed 22.09 magnitude per square arc-seconds! For the first time in 13 trips south of the equator, I observed a bridge of light between the LMC and our Milky Way. I have written a lengthy article of my astro-trip for the Deep-Sky Observer magazine of the Webb Society which will be published this winter or next spring. Here is an excerpt from my article:
"The light bridge of the Large Magellanic Cloud
The journey’s most exciting and unexpected sky phenomenon that we observed, was without a doubt, the light or materia bridge (as I call it) of the Large Magellanic Cloud, LMC. It is not even scientifically studied yet and only a handful of people have reported it in the literature! Lowell astronomer, Brian Skiff, confirmed my description of the ’thing’ and he had seen the bridge from Las Campanas observatory in Chile. US amateur, David Riddle, had noticed this bridge while being in Namibia. Apparently, the first who reported this light bridge in the astronomical literature was the Russian born astronomer Sirgay Gaposchkin in his article The Visual Milky Way in Vistas in Astronomy, vol. 3. He had sketched the object from Mt. Stromlo observatory while he scrutinized the southern Milky Way during the years 1956-57. Isn’t it strange that only northern observers have reported this phenomenon when they have visited the southern hemisphere?
With our unaided eyes, we noted how the light band reached from the LMC, went due south, passed the south celestial pole and continued along a great circle towards the Norma starcloud in the Milky Way. The materia bridge was nearly as wide as LMC itself and more than 40° long. In surface brightness it was comparable to the faintest part of the zodiacal band and maybe half of the gegenschein’s. In the beginning of the night, it reminded me of a waterfall that disappeared into the airglow near the horizon. Later in the night, this phenomenon had rotated clock-wise around the south celestial pole which proved that this was indeed an astronomical feature and followed the earth’s rotation. The materia bridge disappeared in Triangulum Australe, near its alpha star, Atria. It is most remarkable that nobody (as far as I know) has taken photographs of the light bridge! It is neither visible on Axel Mellinger’s panorama of the Milky Way which reaches the surface brightness level of about 24 magnitudes per square arc-second. This phenomenon shall not be confused with the Magellanic Stream which is only visible in radio wavelengths and goes in other direction. My theory is that our observed light bridge is the combined light from millions of faint stars or gas that Milky Way has ripped off from our satellite galaxy due to tidal effects at an earlier close passage. The light can also originate from intergalactic cirrus, like those clouds that can be seen near M81 in extremely deep photographical exposures. Spectroscopic analyses of the light should settle this matter. Curiously enough, the southern celestial pole is involved in a faint band of light while the northern pole, near Polaris, is the starting point of a dark lane in the Milky Way (have you seen it?)."
I suspect a sky capable of showing stars to magnitude 7.5 or has a darkness of about SQM 21.9 is necessary to show the light bridge between the LMC and the Norma Starcloud. Has anyone on this forum seen the bridge of light? It would be very strange if nothing more is known of this naked-eye feature!
Clear Skies!
Timo Karhula
"The light bridge of the Large Magellanic Cloud
The journey’s most exciting and unexpected sky phenomenon that we observed, was without a doubt, the light or materia bridge (as I call it) of the Large Magellanic Cloud, LMC. It is not even scientifically studied yet and only a handful of people have reported it in the literature! Lowell astronomer, Brian Skiff, confirmed my description of the ’thing’ and he had seen the bridge from Las Campanas observatory in Chile. US amateur, David Riddle, had noticed this bridge while being in Namibia. Apparently, the first who reported this light bridge in the astronomical literature was the Russian born astronomer Sirgay Gaposchkin in his article The Visual Milky Way in Vistas in Astronomy, vol. 3. He had sketched the object from Mt. Stromlo observatory while he scrutinized the southern Milky Way during the years 1956-57. Isn’t it strange that only northern observers have reported this phenomenon when they have visited the southern hemisphere?
With our unaided eyes, we noted how the light band reached from the LMC, went due south, passed the south celestial pole and continued along a great circle towards the Norma starcloud in the Milky Way. The materia bridge was nearly as wide as LMC itself and more than 40° long. In surface brightness it was comparable to the faintest part of the zodiacal band and maybe half of the gegenschein’s. In the beginning of the night, it reminded me of a waterfall that disappeared into the airglow near the horizon. Later in the night, this phenomenon had rotated clock-wise around the south celestial pole which proved that this was indeed an astronomical feature and followed the earth’s rotation. The materia bridge disappeared in Triangulum Australe, near its alpha star, Atria. It is most remarkable that nobody (as far as I know) has taken photographs of the light bridge! It is neither visible on Axel Mellinger’s panorama of the Milky Way which reaches the surface brightness level of about 24 magnitudes per square arc-second. This phenomenon shall not be confused with the Magellanic Stream which is only visible in radio wavelengths and goes in other direction. My theory is that our observed light bridge is the combined light from millions of faint stars or gas that Milky Way has ripped off from our satellite galaxy due to tidal effects at an earlier close passage. The light can also originate from intergalactic cirrus, like those clouds that can be seen near M81 in extremely deep photographical exposures. Spectroscopic analyses of the light should settle this matter. Curiously enough, the southern celestial pole is involved in a faint band of light while the northern pole, near Polaris, is the starting point of a dark lane in the Milky Way (have you seen it?)."
I suspect a sky capable of showing stars to magnitude 7.5 or has a darkness of about SQM 21.9 is necessary to show the light bridge between the LMC and the Norma Starcloud. Has anyone on this forum seen the bridge of light? It would be very strange if nothing more is known of this naked-eye feature!
Clear Skies!
Timo Karhula