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Exo-planet collision + Speed of sound on Mars + Fine-structure constant + SuperSecret

#1
C C Offline
James Webb Space Telescope's 1st science targets remain super secret as observatory settles in
https://www.space.com/james-webb-space-t...ons-secret

In the first year of its scientific operations, the James Webb Space Telescope will study small galaxies orbiting the Milky Way, look for the oldest stars in the universe or peer inside mysterious remnants of an exploded star. Its very first science targets, however, remain top secret.


Astronomers See the Wreckage Where Planets Crashed Into Each Other in a Distant Star System
https://www.universetoday.com/155134/ast...ar-system/

EXCERPTS: HD 166191 is a ten million-year-old star about 330 light-years from the Sun. It’s caught astronomers’ attention because it’s a protoplanetary disk transitioning to a debris disk. Years of observations showed a post-collision debris cloud passing in front of the star, giving scientists a novel look at collisions and their aftermath.

The study is titled “A Star-sized Impact-produced Dust Clump in the Terrestrial Zone of the HD 166191 System.” The lead author is Kate Su, an astronomer at Steward Observatory in the University of Arizona. The paper is available online at The Astrophysical Journal.

“By looking at dusty debris disks around young stars, we can essentially look back in time and see the processes that may have shaped our solar system,” Su said in a press release.

The team of astronomers started watching HD 166191 back in 2015. They observed the young solar system more than 100 times between 2015 and 2019. The system is too young to have fully-grown planets, but planetesimals and maybe even dwarf planets are bound to be orbiting the star. Unfortunately, they’re too small and distant to see in telescopes.

But planetesimals are the building blocks of planets. And those blocks don’t accrete in an orderly fashion. Instead, they crash into each other, sometimes shattering into smaller chunks, sometimes melding together to eventually form larger rocky planets.

Those collisions produce dust clouds that are visible in infrared. [...] To produce that much dust, the objects in the collisions had to be as large as dwarf planets. ... “Learning about the outcome of collisions in these systems, we may also get a better idea of how frequently rocky planets form around other stars,” said study lead author Kate Su. Astronomers will keep watching HD 166191 to see how the system develops... (MORE - missing details)


The Speed of Sound on Mars Is Strangely Different, Scientists Reveal
https://www.sciencealert.com/we-now-know...rseverance

EXCERPTS: The speed of sound is not a universal constant. It can change, depending on the density and temperature of the medium through which it travels; the denser the medium, the faster it goes. That's why sound travels about 343 meters (1,125 feet) per second in our atmosphere at 20 degrees Celsius, but also at 1,480 meters per second in water, and at 5,100 meters per second in steel.

Mars' atmosphere is a lot more tenuous than Earth's, around 0.020 kg/m3, compared to about 1.2 kg/m3 for Earth. That alone means that sound would propagate differently on the red planet.

[...] The results back up predictions made using what we know of the Martian atmosphere, confirming that sounds propagate through the atmosphere near the surface at roughly 240 meters per second.

However, the quirk of Mars' shifting soundscape is something completely out of the blue, with conditions on Mars leading to a quirk not seen anywhere else.

"Due to the unique properties of the carbon dioxide molecules at low pressure, Mars is the only terrestrial-planet atmosphere in the Solar System experiencing a change in speed of sound right in the middle of the audible bandwidth (20 Hertz to 20,000 Hertz)," the researchers write.

At frequencies above 240 Hertz, the collision-activated vibrational modes of carbon dioxide molecules do not have enough time to relax, or return to their original state. The result of this is that sound travels more than 10 meters per second faster at higher frequencies than it does at low ones.

This could lead to what the researchers call a "unique listening experience" on Mars, with higher-pitched sounds arriving sooner to the listener than lower ones.

Given that any human astronauts traveling to Mars anytime soon will need to be wearing pressurized spacesuits with comms equipment, or living in pressurized habitat modules, this is unlikely to pose an immediate problem – but it could be a fun concept for science-fiction writers to tinker with... (MORE - missing details)


Life as we know it would not exist without this highly unusual number
https://www.space.com/fine-structure-con...se-mystery

EXCERPTS:: The fine-structure constant is a seemingly random number with no units or dimensions, which has cropped up in so many places in physics, and seems to control one of the most fundamental interactions in the universe.

[...] Its name is the fine-structure constant, and it's a measure of the strength of the interaction between charged particles and the electromagnetic force. The current estimate of the fine-structure constant is 0.007 297 352 5693, with an uncertainty of 11 on the last two digits. The number is easier to remember by its inverse, approximately 1/137.

If it had any other value, life as we know it would be impossible. And yet we have no idea where it comes from... ([url=https://www.space.com/fine-structure-constant-universe-mystery][/url])

https://youtu.be/kNjkBeQ-OAw

https://www.youtube-nocookie.com/embed/kNjkBeQ-OAw
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#2
Kornee Offline
(Mar 25, 2022 05:45 PM)C C Wrote: Life as we know it would not exist without this highly unusual number
https://www.space.com/fine-structure-con...se-mystery

EXCERPTS:: The fine-structure constant is a seemingly random number with no units or dimensions, which has cropped up in so many places in physics, and seems to control one of the most fundamental interactions in the universe.

[...] Its name is the fine-structure constant, and it's a measure of the strength of the interaction between charged particles and the electromagnetic force. The current estimate of the fine-structure constant is 0.007 297 352 5693, with an uncertainty of 11 on the last two digits. The number is easier to remember by its inverse, approximately 1/137.

If it had any other value, life as we know it would be impossible. And yet we have no idea where it comes from... ([url=https://www.space.com/fine-structure-constant-universe-mystery][/url])

https://youtu.be/kNjkBeQ-OAw

https://www.youtube-nocookie.com/embed/kNjkBeQ-OAw
On a whim decided to watch the linked to YT vid:
3:17 to 3:39 he makes an incorrect or at best misleading assertion. Which is obviously false as a general rule. Why? Because the Bohr model inner electron speed/c ratio will be a function of nuclear charge. The higher the charge, the higher that ratio becomes. It's a consequence of (classical) partitioning between PE drop and KE gain in orbital dynamics. -ΔPE = 2ΔKE.

This is reflected in the quantized (atom) case as higher frequency innermost shell photon emission/absorption events as atomic number (thus nuclear charge) goes up. Very well known!
Without bothering to find which specific atomic element corresponds to his fine structure constant 'rule' (hydrogen?), one is reminded not to blindly trust what an authority figure spouts.

PS: At ~ 4:10 mark he casually mentions hydrogen as the case on an energy calculation basis. Which implies that is the true and uniquely true example as per speed ratio assertion in 3:17 to 3:39. Since Bohr model speed and KE are directly linked, this added example is actually superfluous and not a separate relationship re fine structure constant popping up here and there and everywhere.

Then, at ~ 5:58 to 6:10, he blunders again by confusing arbitrarily defined units of measurement with dimensional constants. Nonsense. To be fair he does go on to in essence say it all right, but it's best to just avoid introducing confusion and contradiction in the first place.
Overall I liked his take and especially the great and sometimes humorous use of visuals!
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#3
Kornee Offline
PS2: One more peeve. Sutter goes on about how mysterious it is that the fine structure constant is dimensionless, but that is nonsense. It is dimensionless i.e. a pure ratio by construction!
There are any number of other dimensionless constants that are so by construction. Just take ratios! Wikipedia makes the proper distinction between 'ordinary' dimensionless constants and
'universal' dimensionless constants - ones that, so far, cannot be derived from more fundamental principles:
https://en.wikipedia.org/wiki/Dimensionl...l_constant
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#4
Yazata Offline
(Mar 25, 2022 05:45 PM)C C Wrote: James Webb Space Telescope's 1st science targets remain super secret as observatory settles in
https://www.space.com/james-webb-space-t...ons-secret

In the first year of its scientific operations, the James Webb Space Telescope will study small galaxies orbiting the Milky Way, look for the oldest stars in the universe or peer inside mysterious remnants of an exploded star. Its very first science targets, however, remain top secret.

I assume that there's a process where astronomers apply to get observation time on Webb. Given Webb's design capabilities (assuming it works, which is looking more likely by the day) time on Webb is going to be a highly desirable quantity and the battle to get it is probably going to be pretty competitive. Lots of astronomers aren't going to be pleased that their project wasn't chosen.

So I can see why its managers might not want to get into that can of worms right now, while Webb is still being deployed and calibrated.
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