April 14, 2024 Dear Friends, On this day, 20 years ago and a billion miles from here, Cassini slipped into the large torus of space inhabited by many dozens of small icy bodies, all moving on highly irregular orbits around Saturn. The largest of this flock, Phoebe, at ~133 miles across, was first noticed in 1899. But the remainder weren’t discovered until the eve of the 21
Curiously enough, I have imaged Albiorix and Siarnaq with my 0.4m telescope on La Palma.
Not sure that I have enough SNR at a reasonable cadence to reproduce the light curves. What are their rotational periods? Three days may be possible but 6 hours almost certainly not.
From there, you can go to a webpage for each moon. Tilmann Denk has determined the orbital periods for the two you mentioned: one is 13h20m, the other is 10h11min. Have fun!
I never realised that these objects existed before reading your post. You learn something new every day. I look forward to learning more as your narration of the mission continues. Thank you Carolyn
Nicely explained thanks; I've always liked the irregulars. "We wanted to understand how these outer irregular satellites of Jupiter, at that time known to be only 9 in number, came to be. " But in the 70's we knew of Leda, Himalia, Lysithea and Elara (the 4 progrades, whose names end wit 'a') and Ananke, Carme, Pasiphae and Sinope (the 4 retogrades, whose names end with 'e'). Which one is the 9th?
Josea ... Well, with the help of my colleagues Scott Sheppard (who, with his collaborators, was responsible for discovering most of the irregulars in the outer solar system, including those at Saturn) and Tilmann Denk (the person featured in my post), I can report to you the history of the 9th satellite of the 1970s. It was first sighted in 1975 -- given the designation -- S/1975 J 1 -- but was lost. Two other IAU circulars were issued the same year, reporting some object that *might* be the 9th Jovian irregular. But it wasn't until 2000 that Sheppard and company found an object that was proven to be the one discovered in 1975. Here are the relevant 4 IAU circulars:
Hello. Our paper was published in 1977. The 9th object must have been only very recently discovered because we gave no physical attributes for it. I'm checking on this now. I'll let you know what I find.
Curiously enough, I have imaged Albiorix and Siarnaq with my 0.4m telescope on La Palma.
Not sure that I have enough SNR at a reasonable cadence to reproduce the light curves. What are their rotational periods? Three days may be possible but 6 hours almost certainly not.
Fabulous! Go to https://tilmanndenk.de/outersaturnianmoons/
From there, you can go to a webpage for each moon. Tilmann Denk has determined the orbital periods for the two you mentioned: one is 13h20m, the other is 10h11min. Have fun!
Looks like Albiorix may be possible. Longish period and largish amplitude. Well worth trying, perhaps, when Saturn is once again well placed.
Thanks!
Wonderful discovery!!! Always considered myself slightly “irregular”… and so, find them endearing as well! Thanks Your awesome!!
Hey!!! Wonderful to hear from you! Where are you now? What's your next move?
Thanks Carolyn. Your work helps make our broken little blue dot better.
Now that makes me really happy!
I never realised that these objects existed before reading your post. You learn something new every day. I look forward to learning more as your narration of the mission continues. Thank you Carolyn
You are most welcome! Hope you enjoy the ride from here.
Nicely explained thanks; I've always liked the irregulars. "We wanted to understand how these outer irregular satellites of Jupiter, at that time known to be only 9 in number, came to be. " But in the 70's we knew of Leda, Himalia, Lysithea and Elara (the 4 progrades, whose names end wit 'a') and Ananke, Carme, Pasiphae and Sinope (the 4 retogrades, whose names end with 'e'). Which one is the 9th?
Josea ... Well, with the help of my colleagues Scott Sheppard (who, with his collaborators, was responsible for discovering most of the irregulars in the outer solar system, including those at Saturn) and Tilmann Denk (the person featured in my post), I can report to you the history of the 9th satellite of the 1970s. It was first sighted in 1975 -- given the designation -- S/1975 J 1 -- but was lost. Two other IAU circulars were issued the same year, reporting some object that *might* be the 9th Jovian irregular. But it wasn't until 2000 that Sheppard and company found an object that was proven to be the one discovered in 1975. Here are the relevant 4 IAU circulars:
1975:
http://www.cbat.eps.harvard.edu/iauc/02800/02845.html
http://www.cbat.eps.harvard.edu/iauc/02800/02855.html
http://www.cbat.eps.harvard.edu/iauc/02800/02899.html
2000:
http://www.cbat.eps.harvard.edu/iauc/07500/07525.html
At the moment, Jupiter has 87 known irregular moons. Saturn, with 122, wins!
Fascinating, thanks! t's Themisto: prograde, but smaller orbit than the 'classic' 4 progrades.
Image here http://www.astropalma.com/Projects/Satellites/themisto.html
So it would appear!
Irregulars. Makes me want to hug them!
Ha! My instant thought after seeing the word 'Irregulars': she's going to say, 'Makes me want to eat more fiber!'
Haha! I happen to adore moons. They’re so unappreciated. We must explore them! Plus there’s the cuteness factor!
Hello. Our paper was published in 1977. The 9th object must have been only very recently discovered because we gave no physical attributes for it. I'm checking on this now. I'll let you know what I find.
Superb and easily understood explanation!
Thank you very much!