anything else could account for the redshift in the matter that they saw
I'm just a CS student, but it still sounds pretty reasonable. Element compositions and temperature determine the wavelength of light that will be emitted from the matter. For generic space debris/gasses, the spectra tend to be pretty simple, so we can determine their composition by looking at which frequencies are emitted. Overall variation from the expected wavelengths are caused by the doppler effect (red/blue shifts). (sorry for the physics lecture)
There's really only one cause for 'bogus' redshifts: our expected wavelength for a given band isn't really the right wavelength (i.e. we think we're looking at a shifted band from helium instead of a slightly-shifted sodium band).
This misinterpretation probably won't happen. Relative to earth, matter is moving into the black hole from all directions, one half producing redshifts, the other producing blueshifts, and the region in between producing no shifts at all.
The region producing blueshifts (matter coming towards both us and the black hole) won't really be seen, because it's "behind" the black hole, and its light generally is absorbed inside the event horizon. But we'll still have emissions from matter moving perpendicular (no shift) and away from us (redshifted). We therefore have a background spectrum to compare the redshifts to, and can thereby rule out other sources.
Finally, those speeds are also reasonable. Stuff that we rocket into space can travel over 100,000 mph, and we can do that with the Earth's gravitational pull (Cassini does this tomorrow). Black holes have some serious pull;)
Slashdot Mirror
That's where the aliens are. Better form a government committee to investigate ;)
I'm just a CS student, but it still sounds pretty reasonable. Element compositions and temperature determine the wavelength of light that will be emitted from the matter. For generic space debris/gasses, the spectra tend to be pretty simple, so we can determine their composition by looking at which frequencies are emitted. Overall variation from the expected wavelengths are caused by the doppler effect (red/blue shifts). (sorry for the physics lecture)
There's really only one cause for 'bogus' redshifts: our expected wavelength for a given band isn't really the right wavelength (i.e. we think we're looking at a shifted band from helium instead of a slightly-shifted sodium band).
This misinterpretation probably won't happen. Relative to earth, matter is moving into the black hole from all directions, one half producing redshifts, the other producing blueshifts, and the region in between producing no shifts at all.
The region producing blueshifts (matter coming towards both us and the black hole) won't really be seen, because it's "behind" the black hole, and its light generally is absorbed inside the event horizon. But we'll still have emissions from matter moving perpendicular (no shift) and away from us (redshifted). We therefore have a background spectrum to compare the redshifts to, and can thereby rule out other sources.
Finally, those speeds are also reasonable. Stuff that we rocket into space can travel over 100,000 mph, and we can do that with the Earth's gravitational pull (Cassini does this tomorrow). Black holes have some serious pull ;)