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+--- Thread: Discoveries using the telescopes on Mauna Kea (/showthread.php?tid=17412)
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RE: Discoveries by the telescopes on Mauna Kea - TomK - 09-16-2016
Thanks for the link, Gypsy, but I know Richard Green rather well!
RE: Discoveries by the telescopes on Mauna Kea - Guest - 09-16-2016
Fun Mental Geometry for Wayfinding folks to compare.
http://www2.keck.hawaii.edu/inst/common/TelLimits.html
RE: Discoveries by the telescopes on Mauna Kea - TomK - 09-16-2016
"Fun Mental Geometry for Wayfinding folks to compare.
http://www2.keck.hawaii.edu/inst/common/TelLimits.html"
Sorry, but I think only a complete whackjob would think that the Keck pointing limits are a discovery.
RE: Discoveries by the telescopes on Mauna Kea - Guest - 09-16-2016
Dear Tom,
Just as I investigated tonight, I urge you learn a little bit about Wayfinding and Celestial Navigation before calling someone a "whackjob"
The info I posted is indeed a "discovery " for those who never knew Kecks limitations. Especially when compared to what we can see.
+ I bet some here who are not even into the above would still find the info interesting as it relates. I for one was stoked to read about the operational range.
RE: Discoveries by the telescopes on Mauna Kea - TomK - 09-16-2016
Then start a thread about the discoveries you've made about the Mauna Kea observatories.
RE: Discoveries by the telescopes on Mauna Kea - Guest - 09-17-2016
TomK
Punatic
USA
4583 Posts
Posted - 09/17/2016 : 03:56:45
Then start a thread about the discoveries you've made about the Mauna Kea observatories.
and you used "whackjob" because ????
ETA, no one else is allowed to post fun stuff or opinions on this thread ? B.C. that's what it's looking like. chillaxe man, and go check out Mau Piailug up on Mauna Kea. The research and journey will "educate" you.
RE: Discoveries by the telescopes on Mauna Kea - TomK - 09-18-2016
Another non-discovery, but a beautiful photograph of the Kecks observing the center of the Milky Way. The lasers are used to create an "artificial guide star" which allows the Keck adaptive optics to correct for telescope aberrations and turbulence in the atmosphere. The technology allows ground-based telescopes to produce sharper images than current space-based observatories which don't have to deal with the atmosphere.
http://dailytexanonline.com/2016/09/19/300-mcdonald-observatory-astrophotographer-shoots-for-the-stars
RE: Discoveries by the telescopes on Mauna Kea - Guest - 09-18-2016
Some other fascinating info about Space Based Webb and Hubble.
Webb often gets called the replacement for Hubble, but we prefer to call it a successor. After all, Webb is the scientific successor to Hubble; its science goals were motivated by results from Hubble. Hubble's science pushed us to look to longer wavelengths to "go beyond" what Hubble has already done. In particular, more distant objects are more highly redshifted, and their light is pushed from the UV and optical into the near-infrared. Thus observations of these distant objects (like the first galaxies formed in the Universe, for example) requires an infrared telescope.
This is the other reason that Webb is not a replacement for Hubble is that its capabilities are not identical. Webb will primarily look at the Universe in the infrared, while Hubble studies it primarily at optical and ultraviolet wavelengths (though it has some infrared capability). Webb also has a much bigger mirror than Hubble. This larger light collecting area means that Webb can peer farther back into time than Hubble is capable of doing. Hubble is in a very close orbit around the earth, while Webb will be 1.5 million kilometers (km) away at the second Lagrange (L2) point.
How Far Will Webb See?
Wavelength
Webb will observe primarily in the infrared and will have four science instruments to capture images and spectra of astronomical objects. These instruments will provide wavelength coverage from 0.6 to 28 micrometers (or "microns"; 1 micron is 1.0 x 10-6 meters). The infrared part of the electromagnetic spectrum goes from about 0.75 microns to a few hundred microns. This means that Webb's instruments will work primarily in the infrared range of the electromagnetic spectrum, with some capability in the visible range (in particular in the red and up to the yellow part of the visible spectrum).
The instruments on Hubble can observe a small portion of the infrared spectrum from 0.8 to 2.5 microns, but its primary capabilities are in the ultra-violet and visible parts of the spectrum from 0.1 to 0.8 microns.
Why are infrared observations important to astronomy? Stars and planets that are just forming lie hidden behind cocoons of dust that absorb visible light. (The same is true for the very center of our galaxy.) However, infrared light emitted by these regions can penetrate this dusty shroud and reveal what is inside.
Size
Hubble is 13.2 meters (43.5 ft.) long and its maximum diameter is 4.2 meters (14 ft.) It is about the size of a large tractor-trailer truck.
By contrast, Webb's sunshield is about 22 meters by 12 meters (69.5 ft x 46.5 ft). It's about the size of a tennis court!
Webb will have a 6.5 meter diameter primary mirror, which would give it a significant larger collecting area than the mirrors available on the current generation of space telescopes. Hubble's mirror is a much smaller 2.4 meters in diameter and its corresponding collecting area is 4.5 m2, giving Webb around 7 times more collecting area! Webb will have significantly larger field of view than the NICMOS camera on Hubble (covering more than ~15 times the area) and significantly better spatial resolution than is available with the infrared Spitzer Space Telescope.
Orbit
The Earth is 150 million km from the Sun and the moon orbits the earth at a distance of approximately 384,500 km.
The Hubble Space Telescope orbits around the Earth at an altitude of ~570 km above it.
Webb will not actually orbit the Earth - instead it will sit at the Earth-Sun L2 Lagrange point, 1.5 million km away! Because Hubble is in Earth orbit, it was able to be launched into space by the space shuttle. Webb will be launched on an Ariane 5 rocket and because it won't be in Earth orbit, it is not designed to be serviced by the space shuttle.
At the L2 point Webb's solar shield will block the light from the Sun, Earth, and Moon. This will help Webb stay cool, which is very important for an infrared telescope. As the Earth orbits the Sun, Webb will orbit with it - but stay fixed in the same spot with relation to the Earth and the Sun,
How Far Will Webb see?
Because of the time it takes light to travel, the further away an object is, the further back in time we are looking.
This illustration compares various telescopes and how far back they are able to see. Essentially, Hubble can see the equivalent of "toddler galaxies" and Webb Telescope will be able see "baby galaxies". One reason Webb will be able to see the first galaxies is because it is an infrared telescope. The Big Bang caused the universe (and thus the galaxies in it) to expand, so most galaxies are moving away from each other. The most distant (and thus youngest) galaxies are moving away so quickly that the light they emit gets shifted towards the red end of the spectrum. This is very similar to listening to a train whistle shifting from higher to lower frequency as it passes by. Because visible light from faraway, quickly moving, “high redshift” galaxies is shifted to the infrared, infrared telescopes, like Webb, are ideal for observing these early galaxies.
What About Herschel?
The Herschel Space Observatory is an infrared telescope built by the European Space Agency - it is currently located at the L2 point (where Webb will be).
The primary difference between Webb and Herschel is wavelength range: Webb goes from 0.6 to 28.5 microns; Herschel goes from 60 to 500 microns. Webb is also larger, with a 6.5 meter mirror vs. Herschel's 3.5 meters.
The wavelength ranges were chosen by different science: Herschel looks for the extremes, the most actively star-forming galaxies, which emit most of their energy in the far-IR. Webb will find the first galaxies to form in the early universe, for which it needs extreme sensitivity in the near-IR.
reading too many about the advantages of space vs. ground
RE: Discoveries by the telescopes on Mauna Kea - TomK - 09-18-2016
AP resorts to plagiarism. What a shock. His entire post was copied from http://jwst.nasa.gov/comparison.html without attribution.
RE: Discoveries by the telescopes on Mauna Kea - Guest - 09-18-2016
Do you really and truly think I wrote that tom ? I put it up for everyone to learn more. NOT take some kind of credit for it.
Do you have any comments on it other than complain about me putting up the info for people to read ?