Starship Asterisk*

Ann wrote: ↑Fri Dec 21, 2018 7:39 am

neufer wrote: ↑Fri Dec 21, 2018 4:26 am
(Unless, of course, a many layered meteor is simply
doing a Salome seven veils strip routine for us.)[/list]

A many layered meteor is doing a Salome seven veils strip routine for us! I like it! Many meteors are indeed seen changing colors! So they are burning off one layer after another in glorious technicolor, aren't they?

Ann wrote: ↑Fri Dec 21, 2018 7:39 am

neufer wrote: ↑Fri Dec 21, 2018 4:26 am
(Unless, of course, a many layered meteor is simply
doing a Salome seven veils strip routine for us.)

A many layered meteor is doing a Salome seven veils strip routine for us! I like it! Many meteors are indeed seen changing colors! So they are burning off one layer after another in glorious technicolor, aren't they?

neufer wrote: ↑Fri Dec 21, 2018 4:26 am
(Unless, of course, a many layered meteor is simply
doing a Salome seven veils strip routine for us.)[/list]

Chris Peterson wrote: ↑Thu Dec 20, 2018 7:44 pm

Ann wrote: ↑Thu Dec 20, 2018 7:04 pm
Okay. Here is another voice - or the same one as the one we heard in the picture that I posted in the other thread? - that claims that iron makes yellow trails and magnesium makes blue-green ones. I don't know which claim is correct!

None of them. And all of them. All of these elements produce multiple emission lines which show up nicely in spectra. And even more dominant are the emission lines from gases in the atmosphere. Combine them all and what we see is typically a very desaturated color- white with a yellow cast or white with a green cast being most common. For the most part, the color that you perceive a meteor to be cannot be used to tell you much of anything about its composition. It tells you more about its altitude and speed than anything else. To determine its composition (and that composition will change with time as the volatile elements burn away and the refractory ones remain) you really need to see the spectrum, not the perceived color.

• The transition from oxygen atom green emission
  to nitrogen molecule red & blue emission at
  100 km (the true edge of space) seems rather obvious.
  
  (Unless, of course, a many layered meteor is simply
  doing a Salome seven veils strip routine for us.)

https://en.wikipedia.org/wiki/Aurora#Visual_forms_and_colors wrote:
Red: At the highest altitudes, excited atomic oxygen emits at 630 nm (red); low concentration of atoms and lower sensitivity of eyes at this wavelength make this color visible only under more intense solar activity. The low number of oxygen atoms and their gradually diminishing concentration is responsible for the faint appearance of the top parts of the "curtains". Scarlet, crimson, and carmine are the most often-seen hues of red for the auroras.

Green: At lower altitudes, the more frequent collisions suppress the 630-nm (red) mode: rather the 557.7 nm emission (green) dominates. Fairly high concentration of atomic oxygen and higher eye sensitivity in green make green auroras the most common. The excited molecular nitrogen (atomic nitrogen being rare due to high stability of the N₂ molecule) plays a role here, as it can transfer energy by collision to an oxygen atom, which then radiates it away at the green wavelength. (Red and green can also mix together to produce pink or yellow hues.) The rapid decrease of concentration of atomic oxygen below about 100 km is responsible for the abrupt-looking end of the lower edges of the curtains. Both the 557.7 and 630.0 nm wavelengths correspond to forbidden transitions of atomic oxygen, slow mechanism that is responsible for the graduality (0.7 s and 107 s respectively) of flaring and fading.

Blue: At yet lower altitudes, atomic oxygen is uncommon, and molecular nitrogen and ionized molecular nitrogen take over in producing visible light emission, radiating at a large number of wavelengths in both red and blue parts of the spectrum, with 428 nm (blue) being dominant. Blue and purple emissions, typically at the lower edges of the "curtains", show up at the highest levels of solar activity. The molecular nitrogen transitions are much faster than the atomic oxygen ones.

Ann wrote: ↑Thu Dec 20, 2018 7:04 pm Okay. Here is another voice - or the same one as the one we heard in the picture that I posted in the other thread? - that claims that iron makes yellow trails and magnesium makes blue-green ones. I don't know which claim is correct!

Ann wrote: ↑Thu Dec 20, 2018 6:11 am The reason why I didn't comment was that I thought I had made a good point about the colors of meteors in a recent APOD discussion thread. But when I checked my post, the picture I posted had disappeared.
...

Ann

Ann wrote: ↑Thu Dec 20, 2018 6:11 am
The reason why I didn't comment was that I thought I had made a good point about the colors of meteors in a recent APOD discussion thread. But when I checked my post, the picture I posted had disappeared.

• 1) Go to their profile (by tapping on their 'user name' at the right of their posts)
  
  2) Tap on "Search user’s posts"
  
  3) Check through recent posts manually... or search for significant word (i.e., 'meteors').

MarkBour wrote: ↑Thu Dec 20, 2018 5:33 am

Ann wrote: ↑Thu Dec 20, 2018 4:52 am Thanks, Mark, I really appreciate it!

Although the kitten was sweet, too.

Ann

Any time, Ann. I thought you might remark on the colors in this image, which I think were quite beautiful.
Perhaps no commentary was needed, but I'm not sure if any processing was needed to end up with those rich colors.

Of course there's a band called "Meteor Cat" which can be seen here.

Ann wrote: ↑Thu Dec 20, 2018 4:52 am Thanks, Mark, I really appreciate it!

Although the kitten was sweet, too.

Ann

MarkBour wrote: ↑Wed Dec 19, 2018 7:58 pm

Odysseus wrote: ↑Wed Dec 19, 2018 4:27 pm

Antony Rawlinson wrote: ↑Wed Dec 19, 2018 12:36 pm The link purporting to show the start of the ionisation trail, under the text "can be seen" is a bit of a disappointment. Is it April 1?

I was a little disappointed as well, but it also made me smile.

Just to be clear (if I'm right) I believe the caption was simply referring to the APOD itself when noting
"... a wind-blown ionization trail ... the start of which can be seen here."
whereas, if they had meant for you to follow a link to find a better image of the start of the trail, it would have been best marked up as:
"... the start of which can be seen here."
Besides, there were two good links to ionization tails/trails/trains already in that sentence.

MarkBour wrote: ↑Wed Dec 19, 2018 7:58 pm

Odysseus wrote: ↑Wed Dec 19, 2018 4:27 pm

Antony Rawlinson wrote: ↑Wed Dec 19, 2018 12:36 pm
The link purporting to show the start of the ionisation trail, under the text "can be seen" is a bit of a disappointment. Is it April 1?

I was a little disappointed as well, but it also made me smile.

Just to be clear (if I'm right) I believe the caption was simply referring to the APOD itself when noting
"... a wind-blown ionization trail ... the start of which can be seen here."

whereas, if they had meant for you to follow a link to find a better image of the start of the trail,
it would have been best marked up as: "... the start of which can be seen here."

https://www.etymonline.com/word/see#etymonline_v_23104 wrote:
<<SEE (v.) Old English seon "to see, look, behold; observe, perceive, understand; experience, visit, inspect" (past tense seah, past participle sewen), from Proto-Germanic *sehwanan (source also of Old Saxon, Old High German sehan, Middle High German, German sehen, Old Frisian sia, Middle Dutch sien, Old Norse sja, Gothic saihwan). Thus see might originally mean "follow with the eyes."

Used in Middle English to mean "behold in the imagination or in a dream" (c. 1200), "to recognize the force of (a demonstration)," also c. 1200. Sense of "escort" (as in to see (someone) home) first recorded 1607 in Shakespeare. Meaning "to receive as a visitor" is attested from c. 1500. Gambling sense of "equal a bet" is from 1590s. See you as a casual farewell first attested 1891. Let me see as a pausing statement is recorded from 1510s.>>

Odysseus wrote: ↑Wed Dec 19, 2018 4:27 pm

Antony Rawlinson wrote: ↑Wed Dec 19, 2018 12:36 pm The link purporting to show the start of the ionisation trail, under the text "can be seen" is a bit of a disappointment. Is it April 1?

I was a little disappointed as well, but it also made me smile.

Odysseus wrote: ↑Wed Dec 19, 2018 4:27 pm

Antony Rawlinson wrote: ↑Wed Dec 19, 2018 12:36 pm
The link purporting to show the start of the ionisation trail, under the text "can be seen" is a bit of a disappointment. Is it April 1?

I was a little disappointed as well...

Antony Rawlinson wrote: ↑Wed Dec 19, 2018 12:36 pm The link purporting to show the start of the ionisation trail, under the text "can be seen" is a bit of a disappointment. Is it April 1?