by neufer » Fri Sep 17, 2021 6:08 pm
johnnydeep wrote: ↑Fri Sep 17, 2021 4:27 pm
1. How can we be sure this was caused by an impact and not by some other mechanism? Stupid question I'm sure, and I'll bet the answer is that there simply is no other known mechanism!
2. This event seems to be different than the ones resulting from the breakup of comet Shoemaker-Levy 9. Did those impacts flash white like this one (presumably seen in visible light here)? I know they all left dark "scars" that later for weeks, but what did they look like upon impact?
"If it walks like a duck and it quacks like a duck, then it must be a duck"
... but locating the tiny late asteroid wouldn't hurt.
https://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9#Impacts wrote:
Comet Shoemaker–Levy 9 was a comet that broke apart in July 1992 and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects. Although the impacts took place on the side of Jupiter hidden from Earth, Galileo, then at a distance of 1.6 AU from the planet, was able to see the impacts as they occurred. Jupiter's rapid rotation brought the impact sites into view for terrestrial observers a few minutes after the collisions.
The first impact occurred at 20:13 UTC on July 16, 1994, when fragment A of the nucleus entered Jupiter's southern hemisphere at a speed of about 60 km/s. Instruments on Galileo detected a fireball that reached a peak temperature of about 24,000 K, compared to the typical Jovian cloudtop temperature of about 130 K, before expanding and cooling rapidly to about 1,500 K after 40 seconds. The plume from the fireball quickly reached a height of over 3,000 km. A few minutes after the impact fireball was detected, Galileo measured renewed heating, probably due to ejected material falling back onto the planet. Earth-based observers detected the fireball rising over the limb of the planet shortly after the initial impact.
Despite published predictions, astronomers had not expected to see the fireballs from the impacts and did not have any idea how visible the other atmospheric effects of the impacts would be from Earth. Observers soon saw a huge dark spot after the first impact. The spot was visible even in very small telescopes, and was about 6,000 km across. This and subsequent dark spots were thought to have been caused by debris from the impacts, and were markedly asymmetric, forming crescent shapes in front of the direction of impact.
Over the next six days, 21 distinct impacts were observed, with the largest coming on July 18 at 07:33 UTC when fragment G struck Jupiter. This impact created a giant [Earth sized] dark spot over 12,000 km across, and was estimated to have released an energy equivalent to 6,000,000 megatons of TNT.>>
[quote=johnnydeep post_id=316751 time=1631896054 user_id=132061]
1. How can we be sure this was caused by an impact and not by some other mechanism? Stupid question I'm sure, and I'll bet the answer is that there simply is no other known mechanism!
2. This event seems to be different than the ones resulting from the breakup of comet Shoemaker-Levy 9. Did those impacts flash white like this one (presumably seen in visible light here)? I know they all left dark "scars" that later for weeks, but what did they look like upon impact?[/quote]
[c][b][i]"[color=#0000FF]If it walks like a duck and it quacks like a duck, then it must be a duck[/color]"[/i][/b]
... but locating the tiny late asteroid wouldn't hurt.[/c][quote=https://en.wikipedia.org/wiki/Comet_Shoemaker%E2%80%93Levy_9#Impacts]
[float=right][img3=A sequence of Galileo images, taken several seconds apart, showing the appearance of the fireball of fragment W on the dark side of Jupiter]https://upload.wikimedia.org/wikipedia/commons/1/1b/SL9ImpactGalileo.jpg[/img3][img3=Hubble Space Telescope images of a fireball from the first impact appearing over the limb of the planet]https://upload.wikimedia.org/wikipedia/commons/f/f5/Impact_fireball_appears_over_the_limb_of_Jupiter.jpg[/img3][/float]
Comet Shoemaker–Levy 9 was a comet that broke apart in July 1992 and collided with Jupiter in July 1994, providing the first direct observation of an extraterrestrial collision of Solar System objects. Although the impacts took place on the side of Jupiter hidden from Earth, Galileo, then at a distance of 1.6 AU from the planet, was able to see the impacts as they occurred. Jupiter's rapid rotation brought the impact sites into view for terrestrial observers a few minutes after the collisions.
The first impact occurred at 20:13 UTC on July 16, 1994, when fragment A of the nucleus entered Jupiter's southern hemisphere at a speed of about 60 km/s. Instruments on Galileo detected a fireball that reached a peak temperature of about 24,000 K, compared to the typical Jovian cloudtop temperature of about 130 K, before expanding and cooling rapidly to about 1,500 K after 40 seconds. The plume from the fireball quickly reached a height of over 3,000 km. A few minutes after the impact fireball was detected, Galileo measured renewed heating, probably due to ejected material falling back onto the planet. Earth-based observers detected the fireball rising over the limb of the planet shortly after the initial impact.
Despite published predictions, astronomers had not expected to see the fireballs from the impacts and did not have any idea how visible the other atmospheric effects of the impacts would be from Earth. Observers soon saw a huge dark spot after the first impact. The spot was visible even in very small telescopes, and was about 6,000 km across. This and subsequent dark spots were thought to have been caused by debris from the impacts, and were markedly asymmetric, forming crescent shapes in front of the direction of impact.
Over the next six days, 21 distinct impacts were observed, with the largest coming on July 18 at 07:33 UTC when fragment G struck Jupiter. This impact created a giant [Earth sized] dark spot over 12,000 km across, and was estimated to have released an energy equivalent to 6,000,000 megatons of TNT.>>
[/quote]