12 ms·

Jupiter has 10 more moons we didn't know about

249 points by oedmarap 8y ago

codeduck 8y ago
Title should read "At least" A planet as massive as Jupiter will have captured lots(1) of objects. 1. Terry Pratchett Troll counting system.
- Jaruzel 8y ago
  I'm gonna paste this in because pterry was a god (small G), and there should be no point ever where a reference to him shall go unnoticed. ‘Everyone knows trolls can’t even count up to four!’ (In fact, trolls traditionally count like this: one, two, three, many, and people assume this means they can have no grasp of higher numbers. They don’t realise that many can BE a number. As in: one, two, three, many, many-one, many-two, many-three, many many, many-many-one, many-many-two, many-many-three, many many many, many-many-many-one, many-many-many-two, many-many-three, LOTS.)
  - fabricexpert 8y ago
    Presumably because trolls only have 4 fingers on each hand?
    - rainbowmverse 8y ago
      There are finger-based counting systems with more than one number per finger. Our average of 10 fingers can handle a lot more than 10 numbers. https://en.wikipedia.org/wiki/Finger-counting https://en.wikipedia.org/wiki/Finger-counting
      - tejtm 8y ago
        And less than a digit per err digit (thumbs included) If I recall there was a Native American base 8 counting system which utilized the space between fingers holding sticks or strings as place holders. Made for a handy octal abacus.
  - dzdt 8y ago
    I take "lots" in that quote to be 100 (base 4) or 16 (base 10). Then Jupiters 79 moons would be counted as "oodles-many-many-many-three" -- assuming "oodles" as 1000 (base 4) or 64 (base 10).
cup-of-tea 8y ago
I wonder if discovering lots of tiny moons will lead to a new definition for moon like what happened with the planets.
- JFFalcon 8y ago
  Yes, perhaps these will be reclassified as satellites and moons will have to be large enough to form spheres under their own gravity. That would mean that Mars would have no moons though.
  - fvdessen 8y ago
    Can you expand a bit on why a satellite would need the planet's gravity to keep a spherical shape ?
    - mnw21cam 8y ago
      No, we're talking about a satellite forming into a sphere under its own gravity, not the planet's. Given a large enough lump of matter, gravity will overcome structural strength and force the material to flow into a roughly spherical shape. On Earth, this happens with the maximum mountain height being a few kilometers, but on Mars' moons, which are much smaller, the gravity is far too weak to overcome the rock's structure, and they are basically strange shaped rock things.
      - saagarjha 8y ago
        Is the maximum height of mountains on Earth really due to gravity or a limit imposed by geological weathering?
        rsynnott 8y ago
        A bit of one, a bit of the other, AFAIK. Of course, having geological weathering is also a function of gravity; small objects don't have the atmosphere for it.
        deleted 8y ago
walrus01 8y ago
For reference: https://en.wikipedia.org/wiki/Moons_of_Jupiter https://en.wikipedia.org/wiki/Moons_of_Jupiter Its gravitational field is so huge that it is basically the vacuum cleaner of the solar system. Also a lot of things that are not in orbit of it are occasionally significantly perturbed in their solar orbits, by Jupiter, such as a number of long period comets.
- tomp 8y ago
  How exactly does that work though? An orbit can't just change from a parabola into an ellipse, without the influence of external forces. Is something slowing down these object so that Jupiter "catches" them? (Rings?)
  - Symmetry 8y ago
    You're right that in a two body system this is totally impossible. But for a three body system of Jupiter, the Sun, and our new moon then ballistic capture will baaaasically get you into orbit and then it only takes a small further interaction with another planet, another moon, or whatever to get into orbit the rest of the way.
    - ars 8y ago
      > the Sun Jupiter is in a stable orbit about the Sun, I don't think you can use the Sun as the 3rd body, you need another moon or other object.
      - Symmetry 8y ago
        The important thing, as far as I understand it, is the way the future moon slowly transitions from being primarily under the gravitational influence of the Sun to primarily under the orbital influence of Jupiter. We've actually used ballistic transport to transition probes from orbit around the Earth to basically in orbit around the Moon with just a tiny braking burn at the far side instead of the serious burn that a Holman Transfer orbit would require. And the Moon is in a stable orbit around the Earth and doesn't have any further satellites.
rezeroed 8y ago
"All the newfound moons are small, between about 1 and 3 kilometres across. Seven of them travel in remote orbits more than 20 million kilometres away from Jupiter" As a layman with no astronomical credibilty I'd call those satellites, not moons.
- nikbackm 8y ago
  https://www.spaceanswers.com/solar-system/what-is-the-smallest-size-a-satellite-can-become-a-moon/ https://www.spaceanswers.com/solar-system/what-is-the-smalle...
  - baxtr 8y ago
    From the above article: So as it stands, a moon is simply any natural body in orbit around a planet or other non-stellar object (so asteroids can have moons, and it’s even possible for a moon to have its own moon, although none have been discovered so far).
- maxerickson 8y ago
  Behemoth ISS is 0.0728 kM across. But moon anyway mostly just means natural satellite.
- baseethrowaway 8y ago
  Natural satellite == moon. "Natural satellite" is a subset of "satellite", thus what you'd call them is correct by definition. Let's let the astronomers with credibility play and name the objects.
  - dalbasal 8y ago
    Do astronomers get as fiery about taxanomy as biologists do? I kind of had the impression they're easy going about naming, just more wary of upsetting young enthusiests. I heard there were many sternly worded letters from 9 year olds, after the demotion of Pluto. Slightly related, are all the particles in (eg) Saturn's rings wver referred to as moons?
Shazbaht 8y ago
This is a great example of the hubris of scientists that non-scientists can’t stand. Most believe Pluto is a planet. Moons are rocks in orbit around planets, etc. Why the obsession to change these names? Brings painful thoughts of our future if this is what they care about.
- oblio 8y ago
  Science evolves. Backwards compatibility is good, but then again, the imperial system :D Sometimes it's a good idea to break with the past. Regarding Pluto: https://www.youtube.com/watch?v=BKoRt-6pjAE&vl=en https://www.youtube.com/watch?v=BKoRt-6pjAE&vl=en
  - Arnt 8y ago
    The metric system has broken with its own past, though. The breaks were true breaks, not just elaborations, but they were executed with great care for compatibility. 1m has been defined in four or five different ways, depending on how you count. There's a lesson here: There is a middle ground between preserving legacy and causing problems by deprecation.
    - danso 8y ago
      So what are the “problems by deprecation” you see in the current context of redefining Pluto as not a planet? Having to reprint interplanetary tourism guides?
      - Arnt 8y ago
        It's just another minor thing to complain about for the people who like to complain about science. Nothing minor is major. Some of them are minor and worthwhile, some are minor and not.
- wool_gather 8y ago
  The hubris of revising technical definitions that they themselves created to describe their own work? What are you on about? "Most believe Pluto is a planet" because they were told that by scientists in the first place. Without astronomers, "most" wouldn't even know Pluto existed.
walrus01 8y ago
Fun fact, asteroids in the belt can also have natural satellites: https://en.m.wikipedia.org/wiki/87_Sylvia https://en.m.wikipedia.org/wiki/87_Sylvia
wlesieutre 8y ago
Other recent articles I saw about this said twelve, this one says ten. Anyone know why? https://www.npr.org/2018/07/17/629396121/galileo-would-be-stunned-jupiter-now-has-79-moons https://www.npr.org/2018/07/17/629396121/galileo-would-be-st... If you look at Wikipedia's list and sort by year of discovery, 10 would include the ones in 2018 and 2017, while 12 includes two more in 2016. All 12 are discovered by Sheppard et al. Perhaps those two aren't news anymore?
- bmm6o 8y ago
  Right, they are talking about roughly the same discoveries but some include 2 more: https://astronomy.stackexchange.com/questions/26999/did-we-discover-10-or-12-new-moons-of-jupiter https://astronomy.stackexchange.com/questions/26999/did-we-d...
largespoon 8y ago
Just like I predicted!
sk_hazratali 8y ago
Great news. The planet now has 79 known moons, including a tiny oddball on a collision course with its neighbours. https://www.sherekhudahazratali.com/2017/01/hazrat-abdul-qadir-jilani-ra-quotes.html https://www.sherekhudahazratali.com/2017/01/hazrat-abdul-qad...
joshe 8y ago
The eighth moon sounds exciting... "it travels in the same region of space as the retrograde moons, but in the opposite direction... That means it could easily smash into the retrograde moons, pulverising itself into oblivion." Setting up science nerds for thousands of years of suspense!
- MrLeap 8y ago
  Wouldn't it be a spooky experience to stand on one moon, and have another pass close enough for you to touch it? If they were of similar mass my intuition is that you'd go weightless while it was happening. Might be best to be harnessed during something like that. While I'm thinking about spooky space stories. Jupiter creeps me right the hell out. Thinking about being on one of its moons where Jupiter takes up a HUGE percentage of your visible sky and is just screaming radiation at you. Personify the gas giant a little and you've got a decent proxy for hell. https://solarsystem.nasa.gov/resources/184/simulated-view-from-europas-surface-artists-concept/?category=planets_jupiter https://solarsystem.nasa.gov/resources/184/simulated-view-fr...
  - joshe 8y ago
    That would be amazing, it looks like Europa travels at 14 km/s or 31,000 mph. With no atmosphere there would be no sound or pressure wave. And the bodies are probably small enough to not shatter because of the gravity interaction. Escape velocity is about 36,000 mph. So you could see a huge Manhattan size chunk of rock flying at you at rocket speeds. Would be amazing to see it pass by 100 feet above you.
    - ars 8y ago
      > Would be amazing to see it pass by 100 feet above you. At those speeds, and the necessary angle, I'm not convinced you would be able to see it at all. The actual encounter would last for too short of a time to see (like trying to see a bullet in flight), and their motion would take them out of your field of view, unless the planet you were on was rotating very fast.
carrja99 8y ago
Incredible.
albemuth 8y ago
Awesome, new Eclipse IDE versions!
atulatul 8y ago
This reminds me of the discussion(s) on BBC QI (Quite Interesting) about 'how many moons does the earth have'. A video from QI official channel: https://www.youtube.com/watch?reload=9&v=7qZWM8Aatb8 https://www.youtube.com/watch?reload=9&v=7qZWM8Aatb8 And a compilation of updates over the years. It has Stephen Fry discussing the topic but in recent seasons Sandy Toksvig discussed the topic as well : https://www.youtube.com/watch?v=sGgmmX-dzgU https://www.youtube.com/watch?v=sGgmmX-dzgU
lamarpye 8y ago
There goes the neighborhood.
krylon 8y ago
Is it time to have a Pluto moment for moons? In the end, all such labels are arbitrary, but an calling an object of 2 or 3 km radius a moon feels wrong to me, somehow. Plus, without a lower boundary, pretty much every single chunk of ice in Saturn's rings would count as a moon, so having a formalized definition might come in handy. ;-)
- autokad 8y ago
  well, I certainly think pluto is more of a planet than these are moons
  - dmoy 8y ago
    I think they mean to make a formal definition of moon that would exclude some of the new Jupiter moons, similar to the new formal definition of planet excluding Pluto from being a planet.
- Brockenstein 8y ago
  I got it! Dwarf moons.
- bargl 8y ago
  There is a movement to make anything that isn't a sun capable of being a planet based on only it's own physical characteristics not that of it's location in space. https://www.sciencealert.com/nasa-scientists-have-proposed-a-new-definition-for-planets-and-it-could-change-everything https://www.sciencealert.com/nasa-scientists-have-proposed-a...
- Symmetry 8y ago
  There really isn't any equivalent of the asteroid/planet split that exists for non-moons. We've known about small, non-spherical moons for over a century and nobody has seriously advocated giving a different name for them and the big spherical ones: Luna, Callisto, Ganymede, Europa, Io, Titan, and Triton. But yeah, astronomers will certianly need to figure out some distinction between chunks of ring and discrete moons.
pressurefree 8y ago
its beans and rice not beans and pig feet

249 points by oedmarap 8y ago

Title should read "At least" A planet as massive as Jupiter will have captured lots(1) of objects. 1. Terry Pratchett Troll counting system.

Jaruzel 8y ago
I'm gonna paste this in because pterry was a god (small G), and there should be no point ever where a reference to him shall go unnoticed. ‘Everyone knows trolls can’t even count up to four!’ (In fact, trolls traditionally count like this: one, two, three, many, and people assume this means they can have no grasp of higher numbers. They don’t realise that many can BE a number. As in: one, two, three, many, many-one, many-two, many-three, many many, many-many-one, many-many-two, many-many-three, many many many, many-many-many-one, many-many-many-two, many-many-three, LOTS.)
- fabricexpert 8y ago
  Presumably because trolls only have 4 fingers on each hand?
  - rainbowmverse 8y ago
    There are finger-based counting systems with more than one number per finger. Our average of 10 fingers can handle a lot more than 10 numbers. https://en.wikipedia.org/wiki/Finger-counting https://en.wikipedia.org/wiki/Finger-counting
    - tejtm 8y ago
      And less than a digit per err digit (thumbs included) If I recall there was a Native American base 8 counting system which utilized the space between fingers holding sticks or strings as place holders. Made for a handy octal abacus.
- dzdt 8y ago
  I take "lots" in that quote to be 100 (base 4) or 16 (base 10). Then Jupiters 79 moons would be counted as "oodles-many-many-many-three" -- assuming "oodles" as 1000 (base 4) or 64 (base 10).

cup-of-tea 8y ago

I wonder if discovering lots of tiny moons will lead to a new definition for moon like what happened with the planets.

JFFalcon 8y ago
Yes, perhaps these will be reclassified as satellites and moons will have to be large enough to form spheres under their own gravity. That would mean that Mars would have no moons though.
- fvdessen 8y ago
  Can you expand a bit on why a satellite would need the planet's gravity to keep a spherical shape ?
  - mnw21cam 8y ago
    No, we're talking about a satellite forming into a sphere under its own gravity, not the planet's. Given a large enough lump of matter, gravity will overcome structural strength and force the material to flow into a roughly spherical shape. On Earth, this happens with the maximum mountain height being a few kilometers, but on Mars' moons, which are much smaller, the gravity is far too weak to overcome the rock's structure, and they are basically strange shaped rock things.
    - saagarjha 8y ago
      Is the maximum height of mountains on Earth really due to gravity or a limit imposed by geological weathering?
      - rsynnott 8y ago
        A bit of one, a bit of the other, AFAIK. Of course, having geological weathering is also a function of gravity; small objects don't have the atmosphere for it.
      - deleted 8y ago

walrus01 8y ago

For reference: https://en.wikipedia.org/wiki/Moons_of_Jupiter https://en.wikipedia.org/wiki/Moons_of_Jupiter Its gravitational field is so huge that it is basically the vacuum cleaner of the solar system. Also a lot of things that are not in orbit of it are occasionally significantly perturbed in their solar orbits, by Jupiter, such as a number of long period comets.

tomp 8y ago
How exactly does that work though? An orbit can't just change from a parabola into an ellipse, without the influence of external forces. Is something slowing down these object so that Jupiter "catches" them? (Rings?)
- Symmetry 8y ago
  You're right that in a two body system this is totally impossible. But for a three body system of Jupiter, the Sun, and our new moon then ballistic capture will baaaasically get you into orbit and then it only takes a small further interaction with another planet, another moon, or whatever to get into orbit the rest of the way.
  - ars 8y ago
    > the Sun Jupiter is in a stable orbit about the Sun, I don't think you can use the Sun as the 3rd body, you need another moon or other object.
    - Symmetry 8y ago
      The important thing, as far as I understand it, is the way the future moon slowly transitions from being primarily under the gravitational influence of the Sun to primarily under the orbital influence of Jupiter. We've actually used ballistic transport to transition probes from orbit around the Earth to basically in orbit around the Moon with just a tiny braking burn at the far side instead of the serious burn that a Holman Transfer orbit would require. And the Moon is in a stable orbit around the Earth and doesn't have any further satellites.

rezeroed 8y ago

"All the newfound moons are small, between about 1 and 3 kilometres across. Seven of them travel in remote orbits more than 20 million kilometres away from Jupiter" As a layman with no astronomical credibilty I'd call those satellites, not moons.

nikbackm 8y ago
https://www.spaceanswers.com/solar-system/what-is-the-smallest-size-a-satellite-can-become-a-moon/ https://www.spaceanswers.com/solar-system/what-is-the-smalle...
- baxtr 8y ago
  From the above article: So as it stands, a moon is simply any natural body in orbit around a planet or other non-stellar object (so asteroids can have moons, and it’s even possible for a moon to have its own moon, although none have been discovered so far).
maxerickson 8y ago
Behemoth ISS is 0.0728 kM across. But moon anyway mostly just means natural satellite.
baseethrowaway 8y ago
Natural satellite == moon. "Natural satellite" is a subset of "satellite", thus what you'd call them is correct by definition. Let's let the astronomers with credibility play and name the objects.
- dalbasal 8y ago
  Do astronomers get as fiery about taxanomy as biologists do? I kind of had the impression they're easy going about naming, just more wary of upsetting young enthusiests. I heard there were many sternly worded letters from 9 year olds, after the demotion of Pluto. Slightly related, are all the particles in (eg) Saturn's rings wver referred to as moons?

Shazbaht 8y ago

This is a great example of the hubris of scientists that non-scientists can’t stand. Most believe Pluto is a planet. Moons are rocks in orbit around planets, etc. Why the obsession to change these names? Brings painful thoughts of our future if this is what they care about.

oblio 8y ago
Science evolves. Backwards compatibility is good, but then again, the imperial system :D Sometimes it's a good idea to break with the past. Regarding Pluto: https://www.youtube.com/watch?v=BKoRt-6pjAE&vl=en https://www.youtube.com/watch?v=BKoRt-6pjAE&vl=en
- Arnt 8y ago
  The metric system has broken with its own past, though. The breaks were true breaks, not just elaborations, but they were executed with great care for compatibility. 1m has been defined in four or five different ways, depending on how you count. There's a lesson here: There is a middle ground between preserving legacy and causing problems by deprecation.
  - danso 8y ago
    So what are the “problems by deprecation” you see in the current context of redefining Pluto as not a planet? Having to reprint interplanetary tourism guides?
    - Arnt 8y ago
      It's just another minor thing to complain about for the people who like to complain about science. Nothing minor is major. Some of them are minor and worthwhile, some are minor and not.
wool_gather 8y ago
The hubris of revising technical definitions that they themselves created to describe their own work? What are you on about? "Most believe Pluto is a planet" because they were told that by scientists in the first place. Without astronomers, "most" wouldn't even know Pluto existed.

walrus01 8y ago

Fun fact, asteroids in the belt can also have natural satellites: https://en.m.wikipedia.org/wiki/87_Sylvia https://en.m.wikipedia.org/wiki/87_Sylvia

wlesieutre 8y ago

Other recent articles I saw about this said twelve, this one says ten. Anyone know why? https://www.npr.org/2018/07/17/629396121/galileo-would-be-stunned-jupiter-now-has-79-moons https://www.npr.org/2018/07/17/629396121/galileo-would-be-st... If you look at Wikipedia's list and sort by year of discovery, 10 would include the ones in 2018 and 2017, while 12 includes two more in 2016. All 12 are discovered by Sheppard et al. Perhaps those two aren't news anymore?

bmm6o 8y ago
Right, they are talking about roughly the same discoveries but some include 2 more: https://astronomy.stackexchange.com/questions/26999/did-we-discover-10-or-12-new-moons-of-jupiter https://astronomy.stackexchange.com/questions/26999/did-we-d...

largespoon 8y ago

Just like I predicted!

sk_hazratali 8y ago

Great news. The planet now has 79 known moons, including a tiny oddball on a collision course with its neighbours. https://www.sherekhudahazratali.com/2017/01/hazrat-abdul-qadir-jilani-ra-quotes.html https://www.sherekhudahazratali.com/2017/01/hazrat-abdul-qad...

joshe 8y ago

The eighth moon sounds exciting... "it travels in the same region of space as the retrograde moons, but in the opposite direction... That means it could easily smash into the retrograde moons, pulverising itself into oblivion." Setting up science nerds for thousands of years of suspense!

MrLeap 8y ago
Wouldn't it be a spooky experience to stand on one moon, and have another pass close enough for you to touch it? If they were of similar mass my intuition is that you'd go weightless while it was happening. Might be best to be harnessed during something like that. While I'm thinking about spooky space stories. Jupiter creeps me right the hell out. Thinking about being on one of its moons where Jupiter takes up a HUGE percentage of your visible sky and is just screaming radiation at you. Personify the gas giant a little and you've got a decent proxy for hell. https://solarsystem.nasa.gov/resources/184/simulated-view-from-europas-surface-artists-concept/?category=planets_jupiter https://solarsystem.nasa.gov/resources/184/simulated-view-fr...
- joshe 8y ago
  That would be amazing, it looks like Europa travels at 14 km/s or 31,000 mph. With no atmosphere there would be no sound or pressure wave. And the bodies are probably small enough to not shatter because of the gravity interaction. Escape velocity is about 36,000 mph. So you could see a huge Manhattan size chunk of rock flying at you at rocket speeds. Would be amazing to see it pass by 100 feet above you.
  - ars 8y ago
    > Would be amazing to see it pass by 100 feet above you. At those speeds, and the necessary angle, I'm not convinced you would be able to see it at all. The actual encounter would last for too short of a time to see (like trying to see a bullet in flight), and their motion would take them out of your field of view, unless the planet you were on was rotating very fast.

carrja99 8y ago

Incredible.

albemuth 8y ago

Awesome, new Eclipse IDE versions!

atulatul 8y ago

This reminds me of the discussion(s) on BBC QI (Quite Interesting) about 'how many moons does the earth have'. A video from QI official channel: https://www.youtube.com/watch?reload=9&v=7qZWM8Aatb8 https://www.youtube.com/watch?reload=9&v=7qZWM8Aatb8 And a compilation of updates over the years. It has Stephen Fry discussing the topic but in recent seasons Sandy Toksvig discussed the topic as well : https://www.youtube.com/watch?v=sGgmmX-dzgU https://www.youtube.com/watch?v=sGgmmX-dzgU

lamarpye 8y ago

There goes the neighborhood.

krylon 8y ago

Is it time to have a Pluto moment for moons? In the end, all such labels are arbitrary, but an calling an object of 2 or 3 km radius a moon feels wrong to me, somehow. Plus, without a lower boundary, pretty much every single chunk of ice in Saturn's rings would count as a moon, so having a formalized definition might come in handy. ;-)

autokad 8y ago
well, I certainly think pluto is more of a planet than these are moons
- dmoy 8y ago
  I think they mean to make a formal definition of moon that would exclude some of the new Jupiter moons, similar to the new formal definition of planet excluding Pluto from being a planet.
Brockenstein 8y ago
I got it! Dwarf moons.
bargl 8y ago
There is a movement to make anything that isn't a sun capable of being a planet based on only it's own physical characteristics not that of it's location in space. https://www.sciencealert.com/nasa-scientists-have-proposed-a-new-definition-for-planets-and-it-could-change-everything https://www.sciencealert.com/nasa-scientists-have-proposed-a...
Symmetry 8y ago
There really isn't any equivalent of the asteroid/planet split that exists for non-moons. We've known about small, non-spherical moons for over a century and nobody has seriously advocated giving a different name for them and the big spherical ones: Luna, Callisto, Ganymede, Europa, Io, Titan, and Triton. But yeah, astronomers will certianly need to figure out some distinction between chunks of ring and discrete moons.

pressurefree 8y ago

its beans and rice not beans and pig feet