Coffee House Musing

https://phys.org/news/2022-04-webb-temperature.htmlJWST is in position and is almost ready for real work. The almost part is the final temperature and alignment of the mirrors.JWST sees in the infrared spectrum for science reasons. To keep the scope itself from emitting excess infrared signals JWST needs to be very cold. All the instruments and optics have been brought to their operating temperature. MIRI, the mid-range infrared detector, the major capability the JWST was built to see, has been cooled to under 7 K. But the mirrors are still too hot.One of JWST's goals is to capture the light that was emitted in the very early universe, 13.8 billion years ago. That light has stretched so far into the infrared that the heat emitted by the instrument itself will overwhelm the desired signal if not cooled down enough.

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Currently, four of the 18 mirror segments are above 50 Kelvin: at 52.6, 54.2, 54.4, and 54.5. These four mirror segments emit some mid-infrared light that reaches the MIRI detectors. Since all the mirror temperatures are now below 55 Kelvin, it is expected that MIRI will be sensitive enough to perform its planned science, but any additional cooling of these mirrors will only enhance its performance. The Webb team hopes to see the mirrors cool by an additional 0.5 to 2 Kelvin.

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Beryllium, from which the mirrors are made, cools very slowly. Photons need to be shed by passive means alone. The last few kelvin bleeding off the mirrors will take a few more weeks to come down to optimal temperature.Patience, grasshopper. Almost there.Edited by AZPaul3, : No reason given.

Edited by AZPaul3, : No reason given.

The LHC is back online and all set to bust some dangling participles or something.

I just read about a guy who discovered unauthorized copies of his webpages about extreme macro photography were being posted in mainland China, so he added a Taiwanese flag to the last line of his pages. There is something satisfying imagining the cyber thief receiving poetic justice.

Joints always seemed wasteful to me. I tried lots of different glass and brass pipes though. OK, is indica for sleep or do you alternate to capitalize on the characters of each? The closer you can make it resemble a mad scientist's lab the more fun it is! Yes it is and it's happening so swiftly that we are having problems getting any kind of accurate baselines to compare population densities with. Museum collections, while a wonderful resource, don't really give us a feeling for population densities.One of the consequences of climate change that has only recently started to be appreciated is that insects and their host plants are getting out of synchronization and we're seeing the same thing happen with birds nesting times and insects life stages getting out of synch.A nuclear war or a runaway greenhouse could possibly wipe out the insects, but I can't imagine our extinction would have an impact beyond the decline in vast landscapes of a few dozen crop plants.

As heat continues to bleed off the scope the instruments and adjustments are in the final stages of test and alignment. This article gives us an idea of the complexity of the instruments and the sensitivity of their readings.Examining the heart of Webb: The final phase of commissioning And this is an example of just one of JWST's capabilities.The details of the commissioning are as fascinating as they are complex. JWST is much more highly complex than most people realize. It's not just a swiss army knife unfolding in space, it is more a fine swiss watch with 20 stems on it for ultrafine adjustments.The promise of detailed knowledge from this thing is staggering.

an awesome video of Phobos crossing the sun from Mars' point of view (Perseverance).https://apod.nasa.gov/apod/ap220509.htmlthose dudes at the JPL are so on the ball!

Edited by xongsmith, : spell that with 2 r's, not 3. okay, thrart then

Ha! My moon is bigger than your moon. Take that god of war!

I mean, imagine planning to have Perseverance in the annular eclipse path before you even launch it! Wow to JPL.I'm gonna have enough trouble getting to upstate NY, west coast of Lake Champlain in 2024 to see the Total there unless I can get my son to drive me and he is free on that date, April 8th, 2024 around 3:20pm. I have never seen a Total. Lots of Partials with the pinhole in the long box onto a sheet of paper, but never in my 76 years (it would be 78 then) a Total.Info says it's cloudy 70% of the time under the maximum line. Wrong! It's 100% raining if I'm there and a gorgeous clear sunny day if I'm not.

Edited by xongsmith, : change sea to see: too many Xong game Sea Snakes in my mind these days

Edited by xongsmith, : WELL EXCUSE ME! it's spelled perseverance, not perserverance...

Meet Sagittarius A* – Astronomers Reveal First Image of the Black Hole at the Heart of the Milky Way

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Today, at simultaneous press conferences around the world, including at the European Southern Observatory (ESO) headquarters in Germany, astronomers have unveiled the first image of the supermassive black hole at the center of our own Milky Way galaxy. This result provides overwhelming evidence that the object is indeed a black hole and yields valuable clues about the workings of such giants, which are thought to reside at the center of most galaxies. The image was produced by a global research team called the Event Horizon Telescope (EHT) Collaboration, using observations from a worldwide network of radio telescopes.

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The image is a long-anticipated look at the massive object that sits at the very center of our galaxy. Scientists had previously seen stars orbiting around something invisible, compact, and very massive at the center of the Milky Way. This strongly suggested that this object — known as Sagittarius A* (Sgr A*, pronounced “sadge-ay-star”) — is a black hole, and today’s image provides the first direct visual evidence of it.

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Although we cannot see the black hole itself, because it is completely dark, glowing gas around it reveals a telltale signature: a dark central region (called a shadow) surrounded by a bright ring-like structure. The new view captures light bent by the powerful gravity of the black hole, which is four million times more massive than our Sun.

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A nice article describing Webb's instruments and what sorts of targets each will look at, written by Jonathan Gardner, Webb deputy senior project scientist, NASA’s Goddard Space Flight Center. Seventeen Modes to Discovery: Webb Space Telescope’s Final Commissioning ActivitiesThere are 17 different instruments modes. This observatory is going to do a shitload more than just take pretty pictures!!!

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With the telescope optics and instruments aligned, the Webb team is now commissioning the observatory’s four powerful science instruments. There are 17 different instrument “modes” to check out on our way to getting ready for the start of science this summer. Once we have approved all 17 of these modes, NASA’s James Webb Space Telescope will be ready to begin scientific operations!

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In this article we’ll describe the 17 modes, and readers are encouraged to follow along as the Webb team checks them off one by one on the Where is Webb tracker. Each mode has a set of observations and analysis that need to be verified, and it is important to note that the team does not plan to complete them in the order listed below. Some of the modes won’t be verified until the very end of commissioning.

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For each mode we have also selected a representative example science target that will be observed in the first year of Webb science. These are just examples; each mode will be used for many targets, and most of Webb’s science targets will be observed with more than one instrument and/or mode. The detailed list of peer-reviewed observations planned for the first year of science with Webb ranges from our solar system to the most distant galaxies.

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There is also an amazing diagram showing the light paths to the various instruments.

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The beam of light coming from the telescope is then shown in deep blue entering the instrument through the pick-off mirror located at the top of the instrument and acting like a periscope.
Then, a series of mirrors redirect the light toward the bottom of the instruments where a set of 4 spectroscopic modules are located. Once there, the beam of light is divided by optical elements called dichroics in 4 beams corresponding to different parts of the mid-infrared region. Each beam enters its own integral field unit; these components split and reformat the light from the whole field of view, ready to be dispersed into spectra. This requires the light to be folded, bounced and split many times, making this probably one of Webb’s most complex light paths.
To finish this amazing voyage, the light of each beam is dispersed by gratings, creating spectra that then projects on 2 MIRI detectors (2 beams per detector). An amazing feat of engineering!

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It's Brooks Robinson's birthday.

42 years ago, I remember that day vividly. I was at a nearby creek marking specimens of the dragonfly species Epitheca canis for a male territoriality study. I heard or felt thudding, like distant thunder, but had no idea what had happened. We are about 80 airmiles from the mountain. When I got home later in the afternoon my wife was glued to the TV and they were showing recorded videos and live feeds. It was amazing to see helicopter images of a pickup covered in ash with dead bodies in the bed. The stories and photography were amazing. People in Spokane had a couple feet of ash on the ground and no sign when it would stop. They were lucky it was a small eruption. There are places in central Oregon where the pumice deposits from Mt. Mazama are more than 100 feet thick.

I was in Montana that day. They told us the visibility was so bad in Missoula that police were stopping traffic.I live about 850 mi ENE of Mt. St. Helens and we were told not to wash our cars because trying to remove the fine ash would ruin the finish.

A new type of fossil may correct some misunderstandings of past climate and geological history. Scientists Discover “Ghost” Fossils – “Completely Unexpected”

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An international team of scientists from University College London (UCL), the Swedish Museum of Natural History, Natural History Museum (London), and the University of Florence has found a remarkable type of fossilization that has remained almost entirely unnoticed until now.

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The fossils are microscopic imprints, or “ghosts,” of single-celled plankton, called coccolithophores, that lived in the seas millions of years ago, and their discovery is revolutionizing our understanding of how climate change affects plankton in the oceans.

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Coccolithophores are important in today’s oceans, providing much of the oxygen we breathe, supporting marine food webs, and locking carbon away in seafloor sediments. They are a type of microscopic plankton that surround their cells with hard calcareous plates, called coccoliths, and these are what normally fossilize in rocks.

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Declines in the abundance of these fossils have been documented from multiple past global warming events, suggesting that these plankton were severely affected by climate change and ocean acidification. However, a study published today in the journal Science presents new global records of abundant ghost fossils from three Jurassic and Cretaceous warming events (94, 120, and 183 million years ago), suggesting that coccolithophores were more resilient to past climate change than was previously thought.

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“The discovery of these beautiful ghost fossils was completely unexpected,” says Dr. Sam Slater from the Swedish Museum of Natural History. “We initially found them preserved on the surfaces of fossilized pollen, and it quickly became apparent that they were abundant during intervals where normal coccolithophore fossils were rare or absent – this was a total surprise!”

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“Normally, paleontologists only search for the fossil coccoliths themselves, and if they don’t find any then they often assume that these ancient plankton communities collapsed,” explains Professor Vivi Vajda (Swedish Museum of Natural History). “These ghost fossils show us that sometimes the fossil record plays tricks on us and there are other ways that these calcareous nannoplankton may be preserved, which need to be taken into account when trying to understand responses to past climate change.”

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NASA says JWST will release its first full spectrum pics on July 12. These are still test pics, and the buzz is these are going to be exceptional, but this is the last of them. Everything after that is for the science.And it's been hit by a small boulder. Everyone says that is minor and not unexpected and they even call it a micrometeoroid. It's a damn boulder.Ok, they are the smart guys, but the scope hasn't been up there all that long and it's already got a ding? That probability spread seems a little front loaded to me. This thing is supposed to last forever, give or take 15 years. That is the existential dread I fear most for this scope and I cringe everytime I think of it.James Webb Space Telescope suffers 1st noticeable micrometeoroid impact just months into flight