Science Bulletins: Sloan Digital Sky Survey-Mapping the Universe
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- Опубликовано: 15 окт 2024
- Taking a census of all the luminous objects in one-quarter of the visible cosmos is a hefty accounting job. It takes a specially-built telescope on task every clear night for eight years, wielding one of the biggest digital cameras on the planet. Over a hundred million stars, galaxies, and quasars have been tallied so far. Meet the astronomical observers and theorists set on divining the three-dimensional structure and origins of the Universe from these unprecedented scores of data.
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I am impressed by the epic commitment to thoroughness.
Nice video. Makes you wonder who and how these apparently exotic scientific ventures are funded. The footage of the structure moving on and off the telescope rather than the other way around is interesting.
The funders are the national science foundation for their biggest contributors to a lot of research and development projects John Hopkins University in a combination of Harvard UniversityA consortium of international contributors from around the world whether I contribute what scientist who participate in a research project or direct funding
The Alfred P. Sloan foundation did a chunk of the funding and hence the name was changed
Lovely, thanks for sharing. This is next level with low errors.
I still don't understand how this works... So data is being sent to a drill that makes holes of different sizes on a plate - I'm confused as to a) how they can just shine light through it and get distance data b)how they have optic cables that fit every size hole. This is the 3rd place I came to try and have these questions answered I can't figure it out
No... I can't either. I've seen several PBS documentaries. Why do you need the metal plate for relative distancees.
The only thing I can think of, is the the wires transmitted different current that are relative to the brightness of the objects viewed. And the holes are the possisions of the said objects. But I have no scientific training at all.
The plates are used only for the spectrographic operations of the 2.5m telescope. The holes in the plates correspond to positions of target objects and optical fibers are inserted into the holes. The fibers connect to powerful spectrographs with different spectral dispersions and different spectral regions.
Separating the light from target objects into their unique spectra provide vastly more data about the source than a mere image. Everything from the chemical composition, to the temperature, the strength of magnetic fields, to the line-of-sight motions of the objects (with respect to the observer) are measurable with spectrographic observations of astronomical objects. And whereas it was wonderful when spectrographs were first applied to observe one object at a time with a large telescope, it is orders of magnitude better to collect HUNDREDS of spectra every hour of every night of telescope time. (This was the goal of the SDSS project. The folks who conceived, designed and operated the scope hit the ball out of the proverbial ball park. The spectrographic observations are routinely conducted with the efficiency of Japanese automobile assembly plants. Science at the SDSS is done with business-like efficiency. But I digress.)
There are only two different size holes in the plug plates; accommodating either a single fiber or a small bundle of fibers. The latter are used to gather light from an object like a galaxy and they allow to collect a bunch of spectra from that galaxy sampling the innermost regions near the core of the galaxy and regions at different distances from the core. The spectra reveal the different aged stellar populations, gas clouds, and, crucially, the velocities, towards or away from us, of those different stellar populations and gas clouds. The cool thing about this capability is it allows us to detect populations of stars which are the results of collisions and mergers of galaxies long after those collisions or mergers. And, by mapping the velocity of stellar populations at different distances from the cores of their host galaxies, we can detect the presence of super-massive black holes at the centers of those galaxies. Surveying tens of thousands of galaxies allows us to know how rare or ordinary black holes are in galaxies.
I hope this answered your question.
@@trimetrodon so, they take an image of “square A” of the night sky. The data is then sent out to have a plate made of it where holes are drilled corresponding to certain celestial objects they want to catch the spectra of. After that the holes which correspond to the objects of interest are plugged w optical fibers and the plate is inserted back into a telescope which is then pointed back at the same “square A” patch of sky initially observed?
@@thunderdrumandbass Yes, you’ve got it. :)
@@robandrews4815 look up how they do spectography. They usually use a slit to isolate an object. This is the same thing just a lot more objects at one time.
This is so low-tech and cumbersome. Why not just have a lattice of fiber cables, each with 2 motors to position them to any point within its lattice square, computer controlled. Certainly much cheaper, way faster, and much more flexible.
Factor in cost and jitter and you'll probably see why they use the low-tech method.
That's exactly what's being developed for SDSS-V
Robotic fiber positioners will be installed this year. It is a non-trivial upgrade.
@@trimetrodon Regarding my comment: I guess low-tech and reliable is better than high-tech and error-prone. Things usually aren't as simple as one may think...