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As Hubble Breaks a Distance Record, We Learn Its True Limits
StartsWithABang writes: You might think that, when it comes to finding the most distant objects in the Universe, all we need is a good telescope, to leave the shutter open, and wait. As we accumulate more and more photons, we're bound to find the most distant, faint objects out there. Sure, Hubble just broke its own cosmic distance record, but it's certainly not the most distant. Thinking so misses an important fact: the Universe is expanding! And with that expansion, the wavelength of the light we can see gets redshifted. Ultraviolet light winds up in the infrared, infrared light winds up in the microwave, and the most distant galaxies that are out there are invisible, even to Hubble. Here are Hubble's limits, and how the James Webb Space Telescope will overcome them.
I guess you stumbled on a logical error (and you didn't read the article). 1. Very old light reaches us all the time, not just since the start of the Hubble. Thus light from very far away objects has hit Hubble from the beginning, but we weren't able yet to identify it. So there is a function of time, but it has more to do with our increasing ability to make sense of Hubble data. 2. The article talks mainly about the limits of Hubble. As it has a limited mirror area, the amount of light it can collect is limited. Objects farther away have to be brighter to be visible with Hubble. 3. Hubble works only with light that can be reflected by its mirror. The longest wavelength it can detect is 1 micron. As light that comes from far away is redshifted, its wavelength increases. Usually we use the Lyman series of absorbtion lines of Hydrogenium to measure the redshift. As soon as the shortest wavelength of the Lyman series is redshifted to a wavelength of more than 1 micron, we can't see it anymore in Hubble. Thus the farthest object of which we can estimate the distance with Hubble can't be farther away than the redshift of the Lyman series to 1 micron allows. Yes, also X ray can be redshifted to UV and to visible light, which then could be detected by Hubble, but we can't measure the redshift (yet), because we don't know how to identify the absorbtion lines that exists in X rays.
Why is the parent modded down when the post is correct and politely stated?
The GP, at this time, is not modded down. The GP has a history of down modded posts causing bad karma and a low score on new posts.
And looking at the GP's history, this seems to be one of the few times where the post mentions red shift in open-endedly, instead of proposing the idea that red shift is caused by different star ages, something that runs completely against basic physics of how red shift works in both observation and the lab.
It's highly relevant to every article about space outside our galaxy
Red shift is not the only distance measure outside of our galaxy. Stories, even on Slashdot, have discussed subtle changes to those other distance measurements and the impact it has on Hubble's law. And while it is relevant to every article, shouldn't be expected to be in every such article, just as not every article that mentions Newtonian mechanics isn't going to discuss the limitations of using an approximation to relativity.
Maybe we have too many professional astronomers with mod points?
Considering how often the first people to post something using large words around here get modded up, even if failing at intro level astronomy stuff, or how people get modded up for dismissing astronomy theories with no actual basis or content in their post, I don't think it is astronomers with mod points we have to worry about.