Explanation: Where are all of these meteors coming from? In terms of direction on the sky, the pointed answer is the constellation of Gemini. That is why the major meteor shower in December is known as the Geminids -- because shower meteors all appear to come from a radiant toward Gemini. Three dimensionally, however, sand-sized debris expelled from the unusual asteroid 3200 Phaethon follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the constellation of Gemini. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Gemini. Featured here, a composite of many images taken during the 2020 Geminids meteor shower shows over 200 bright meteorss that streaked through the sky during the night December 14. The best meteor shower in November, the Leonids, peaks tonight and tomorrow. Unfortunately, this year, dim meteors during the early-morning peak will be hard to see against a sky lit by a bright gibbous moon. Still, a few bright Leonid meteors should be visible each hour.
KING RICHARD II: Down, down I come; like glistering Phaethon,
Wanting the manage of unruly jades.
<<3200 Phaethon is an active Apollo asteroid 5.8 km in diameter with an orbit that brings it closer to the Sun than any other named asteroid. For this reason, it was named after the Greek myth of Phaëthon, son of the sun god Helios. Shortly after its discovery, Fred Whipple observed that the "orbital elements of 1983 TB shown on IAUC 3879 are virtually coincident with the mean orbital elements of 19 Geminid meteors photographed with the super-Schmidt meteor cameras". In other words, Phaethon is the long-sought parent body of the Geminids meteor shower of mid-December. In 2018, observations revealed that Phaethon was blue in color. This is extremely rare, as most asteroids tend to be grey or red. In 2020, polarimentric study revealed Phaeton has a surface with steep slopes covered by a mix of regolith with larger pebbles. Phaethon's composition fits the notion of its cometary origin; it is classified as a F-type asteroid because it is composed of dark material.
Phaethon is an asteroid whose orbit more closely resembles that of a comet; it has been referred to as a "rock comet". In recent studies performed by NASA's STEREO spacecraft, dust tails have been observed, and in 2010, Phaethon was detected ejecting dust. It is possible that the Sun's heat is causing fractures similar to mudcracks in a dry lake bed. This occurs because Phaethon's orbit takes it closer to the Sun than any other named asteroid (0.14 AU at perihelion) causing extreme heating and enough solar radiation pressure to push any separated pieces off the asteroid's surface. Since its discovery, several other objects were found exhibiting mixed cometary and asteroidal features, such as 133P/Elst–Pizarro, leading to a new class of objects dubbed "active asteroids".>>
With downright payment, show'd unto my father.
Now Phaethon hath tumbled from his car,
And made an evening at the noontide prick.
<<In Ovid's Metamorphoses, Phaethon is the son of Clymene and the sun-god Sol, who would often boast about being the son of the sun-god. Phaethon, challenged by Epaphus and his playmates, sought assurance from his mother that his father was Sol indeed. She gave him the requested assurance and told him to turn to his father for confirmation. He asked his father for some proof that would demonstrate his relationship with the sun. When the god swore by the river Styx to grant him whatever he wanted, he insisted on being allowed to drive the sun chariot for a day. Sol tried to talk him out of it by telling him that not even Jupiter (the king of the gods) would dare to drive it, as the chariot was fiery hot and the horses breathed out flames. He said: The first part of the track is steep, and one that my fresh horses at dawn can hardly climb. In mid-heaven it is highest, where to look down on earth and sea often alarms even me and makes my heart tremble with awesome fear. The last part of the track is downwards and needs sure control. Then even Tethys herself, who receives me in her submissive waves, is accustomed to fear that I might dive headlong. Moreover, the rushing sky is constantly turning, and drags along the remote stars, and whirls them in rapid orbits. I move the opposite way, and its momentum does not overcome me as it does all other things, and I ride contrary to its swift rotation. Suppose you are given the chariot. What will you do? Will you be able to counter the turning poles so that the swiftness of the skies does not carry you away? Perhaps you conceive in imagination that there are groves there and cities of the gods and temples with rich gifts. The way runs through the ambush, and apparitions of wild beasts! Even if you keep your course, and do not steer awry, you must still avoid the horns of Taurus the Bull, Sagittarius the Haemonian Archer, raging Leo and Lion's jaw, Scorpio's cruel pincers sweeping out to encircle you from one side, and Cancer's crab-claws reaching out from the other. You will not easily rule those proud horses, breathing out through mouth and nostrils the fires burning in their chests. They scarcely tolerate my control when their fierce spirits are hot, and their necks resist the reins. Beware, my boy, that I am not the source of a gift fatal to you, while something can still be done to set right your request!
Phaethon, however, was adamant, and thus Sol was forced to relent. When the day came, the fierce horses that drew the chariot felt that it was empty because of the lack of the sun-god's weight and went out of control. Terrified, Phaethon dropped the reins. The horses veered from their course, scorching the earth, burning the vegetation, changing much of Africa into a desert, drying up rivers and lakes and shrinking the sea. Earth cried out to Jupiter who was forced to intervene by striking Phaethon with a lightning bolt. Like a falling star, Phaethon plunged blazing into the river Eridanus.>>
King Henry VI, part III: II, vi
CLIFFORD: O Phoebus, hadst thou never given consent
That Phaethon should cheque thy fiery steeds,
Thy burning car never had scorch'd the earth!
Re: APOD: Geminids from Gemini (2021 Nov 16)
Posted: Tue Nov 16, 2021 5:10 pm
by Ann
TheZuke! wrote: ↑Tue Nov 16, 2021 2:33 pm
Thanks for the ANNotation, ANN!
I was unable to find Castor and Pollux in such a busy, topsy-turvy composite!
EDIT: I would like a file of your ANNotations, that would make skyhopping much more enjoyable!
Thanks a million, Zuke! Unfortunately I don't keep any sort of file. Yes, I save my annotated images, but I don't add any explanations to them.
The best way to see my annotations is probably to just save the posts here where I have posted annotated images and explanations.
TheZuke! wrote: ↑Tue Nov 16, 2021 2:33 pm
Thanks for the ANNotation, ANN!
I was unable to find Castor and Pollux in such a busy, topsy-turvy composite!
EDIT: I would like a file of your ANNotations, that would make skyhopping much more enjoyable!
Thanks a million, Zuke! Unfortunately I don't keep any sort of file. Yes, I save my annotated images, but I don't add any explanations to them.
The best way to see my annotations is probably to just save the posts here where I have posted annotated images and explanations.
Ann
I suppose you could make the image and annotations self-contained by adding a text box that includes the annotations.
TheZuke! wrote: ↑Tue Nov 16, 2021 2:33 pm
Thanks for the ANNotation, ANN!
I was unable to find Castor and Pollux in such a busy, topsy-turvy composite!
EDIT: I would like a file of your ANNotations, that would make skyhopping much more enjoyable!
Thanks a million, Zuke! Unfortunately I don't keep any sort of file. Yes, I save my annotated images, but I don't add any explanations to them.
The best way to see my annotations is probably to just save the posts here where I have posted annotated images and explanations.
Ann
I suppose you could make the image and annotations self-contained by adding a text box that includes the annotations.
Sure! That would be me! I'm glad if I can separate my pictures from my documents...
But thanks for your suggestion, which is a very good one, except I'm me...
Sure! That would be me! I'm glad if I can separate my pictures from my documents...
But thanks for your suggestion, which is a very good one, except I'm me...
Ann
I don't mean to pry, but what type of computer do you use to do your Annotations? Windows? Mac? Linux? Something else?
I'm using Windows. And the drive(?) - what do you call it? - that I use is Opera, and also Google Chrome.
Ann
Well, Opera and Chrome are both web browsers. As for the "drive" you mentioned, maybe that's Google Drive, and maybe you're using Google Docs' editing tools? I just tried it for the first time, and it seemed opaque to me and non-intuitive, but I didn't spend a lot of time at it.
I don't mean to pry, but what type of computer do you use to do your Annotations? Windows? Mac? Linux? Something else?
I'm using Windows. And the drive(?) - what do you call it? - that I use is Opera, and also Google Chrome.
Ann
Well, Opera and Chrome are both web browsers. As for the "drive" you mentioned, maybe that's Google Drive, and maybe you're using Google Docs' editing tools? I just tried it for the first time, and it seemed opaque to me and non-intuitive, but I didn't spend a lot of time at it.
No, sorry, I just used the word "drive" when I meant "web browser. Forget about the "drive". As for editing tools, I'm happy as long as I can download images and annotate them.
My interest in spending any appreciable amount of time trying to figure out editing tools is... most limited.
I'm using Windows. And the drive(?) - what do you call it? - that I use is Opera, and also Google Chrome.
Ann
Well, Opera and Chrome are both web browsers. As for the "drive" you mentioned, maybe that's Google Drive, and maybe you're using Google Docs' editing tools? I just tried it for the first time, and it seemed opaque to me and non-intuitive, but I didn't spend a lot of time at it.
No, sorry, I just used the word "drive" when I meant "web browser. Forget about the "drive". As for editing tools, I'm happy as long as I can download images and annotate them.
My interest in spending any appreciable amount of time trying to figure out editing tools is... most limited.
Well, Opera and Chrome are both web browsers. As for the "drive" you mentioned, maybe that's Google Drive, and maybe you're using Google Docs' editing tools? I just tried it for the first time, and it seemed opaque to me and non-intuitive, but I didn't spend a lot of time at it.
No, sorry, I just used the word "drive" when I meant "web browser. Forget about the "drive". As for editing tools, I'm happy as long as I can download images and annotate them.
My interest in spending any appreciable amount of time trying to figure out editing tools is... most limited.
Ann
Ok, but what editing tool do you use?
Heck, what do I know?
I take screenshot. Then I open something called Paint 3D. What's that? I have no idea, as long as I can use it. I copy my screenshot into Paint 3D, and then I use an editing tool that is available.
No, sorry, I just used the word "drive" when I meant "web browser. Forget about the "drive". As for editing tools, I'm happy as long as I can download images and annotate them.
My interest in spending any appreciable amount of time trying to figure out editing tools is... most limited.
Ann
Ok, but what editing tool do you use?
Heck, what do I know?
I take screenshot. Then I open something called Paint 3D. What's that? I have no idea, as long as I can use it. I copy my screenshot into Paint 3D, and then I use an editing tool that is available.
Perfect! Paint 3D is indeed an image editor and is a Microsoft's built-in app that comes with Windows. And with Paint 3D, you can click the "Text" button to insert a text box and type in whatever text you want. If it's a lot of text, type it in elsewhere and then copy/paste into the text box. Like as in this result:
I take screenshot. Then I open something called Paint 3D. What's that? I have no idea, as long as I can use it. I copy my screenshot into Paint 3D, and then I use an editing tool that is available.
Perfect! Paint 3D is indeed an image editor and is a Microsoft's built-in app that comes with Windows. And with Paint 3D, you can click the "Text" button to insert a text box and type in whatever text you want. If it's a lot of text, type it in elsewhere and then copy/paste into the text box. Like as in this result:
APOD November 16 2021 annotated.png
Oooo-kay. I'll try it when I feel up to it. Maybe next time. If I feel like annotating the upcoming APOD, I'll probably refrain from it, because I don't have that much time today, and annotating takes quite some time in the first place, and then figuring out how to insert text into the image.
It took me ages to figure out how to "scale down" a too-large APOD so that I could insert it into a post at Starship Asterisk* without uploading the image to my computer first. I kept pestering poor bystander for help, and after he had first explained it he then sighed every time I asked him again, "I don't understand why you don't get it".
But thanks, Johnny! I really appreciate it!
Ann
Re: APOD: Geminids from Gemini (2021 Nov 16)
Posted: Fri Nov 19, 2021 3:07 pm
by TheZuke!
Thanks Ann!
I've saved your ANNotated image to my Pictures folder!
(Edit: I hope it wasn't too much work for you)
Re: APOD: Geminids from Gemini (2021 Nov 16)
Posted: Fri Nov 19, 2021 3:16 pm
by TheZuke!
So, does this "cometeor" cross the Earth's orbital path at the (relatively) same location every time (well, considering that the "cometeor" and the Earth are moving with The Sun on its journey around the Milky Way)?
Or are these pebbles the remains of just one crossing?
If a large piece should hit the Earth, would it no longer be considered a pebble, but a Bam-Bam?
Re: APOD: Geminids from Gemini (2021 Nov 16)
Posted: Fri Nov 19, 2021 4:09 pm
by johnnydeep
TheZuke! wrote: ↑Fri Nov 19, 2021 3:16 pm
So, does this "cometeor" cross the Earth's orbital path at the (relatively) same location every time (well, considering that the "cometeor" and the Earth are moving with The Sun on its journey around the Milky Way)?
Or are these pebbles the remains of just one crossing?
...
I would say the answers are "yes" and "no" respectively. The orbit of comet 3200 Phaeton is pretty stable (I assume) and is completely within (*) the inner solar system. From Wikipedia:
Aphelion 2.4028 AU (359 million km)
Perihelion 0.13998 AU (20.9 million km)
Semi-major axis 1.2714 AU (190 million km)
Eccentricity 0.88990
Orbital period 523.6 days (1.434 yr)
The Earth passes through the debris trail every year, and the comet leaves more debris every 523 days.
(*) By "within" I only mean within the orbit of Jupiter (which is 4.95 AU x 5.46 AU). 3200 Phaeton apparently still enters the asteroid belt on every orbit:
Geminids from Gemini
I'm glad if I can separate my pictures from my documents... 
