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Rare system of five stars discovered

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Re: Rare system of five stars discovered

#21

Post by andygates »

restalis wrote: post #19
lagadu wrote: post #8

Ok, so objects orbit not other objects but rather centres of gravity. This means that the system in question could have planets with small orbits (like the earth's for example) orbiting that system's centre of mass despite the stars being many AUs away from it. It may be unlikely but it's certainly possible, right? Am I missing something that'd make this impossible? Because that would be incredibly cool! edit: I'm as…

"This means that the system in question could have planets with small orbits (like the earth's for example) orbiting that system's centre of mass despite the stars being many AUs away from it. It may be unlikely but it's certainly possible, right?" No, this does not mean that at all! An orbit asks for a centripetal force. In heliocentric systems this force is the gravity of the star (considering the gravity of the or…

..and if there were inhabitants, they'd be suffering unpredictable chaotic seasonality like the aliens in https://en.wikipedia.org/wiki/The_Three-Body_Problem

Re: Rare system of five stars discovered

#22

Post by leni536 »

lagadu wrote: post #15
leni536 wrote: post #12

Earlier quoted context omitted.

Orbiting around the center of gravity only can be applied for two body systems. For many body systems it can be applied too as a careful approximation (like in the article). The movement of a small planet in the middle couldn't be described by this however, since it's an approximate three body system now (the two pairs and the planet)- There could be stable point's in the middle, I don't know about that. Most certain…

Looking into it, couldn't a planet orbit one of the two stable Lagrange points between the two groups, L4 and L5? That wouldn't be "inside" the orbit though :(

Yeah, I would think that the quasi stable orbits would be L4, L5 or orbiting around any of the pairs. If you have a symmetric situation isn't the middle point exactly L1? That would be unstable.

Edit: From Wikipedia:

>The triangular points (L4 and L5) are stable equilibria, provided that the ratio of M1/M2 is greater than 24.96.

So with a symmetric situation, where M1/M2=1 they wouldn't be stable either.

Re: Rare system of five stars discovered

#23

Post by a3n »

vacri wrote: post #10

Five-star systems aren't rare at all, in fact, they're problematically common. Usually the issue is that with such a limited array of choices, people gravitate to one star or five stars, and you don't get much meaningful information from the resulting scores. Percentage-based systems give more flexibility and have a wider 'active zone', without being overwhelmingly complex - and people are much less likely to given m…

Would orbit again.

Re: Rare system of five stars discovered

#24

Post by rimunroe »

pluma wrote: post #16
mixmastamyk wrote: post #7

Earlier quoted context omitted.

Their center of gravity, say about here: o O---------------o ^ Pluto and Charon do it as well, even Earth and Moon to a small degree.

I've actually heard someone argue that because of this the moon is actually not a moon but our sister planet.

All orbits go around a common center of mass which is not the center of mass of the orbiting bodies separately. The Earth-Moon center of mass is still located within the Earth.

[edit] I forgot to mention that the distinction between a satellite/moon and another co-orbiting body had to do with the location of that barycenter being within one of their bodies, if I recall correctly.

Re: Rare system of five stars discovered

#25

Post by chiph »

andygates wrote: post #21
restalis wrote: post #19

Earlier quoted context omitted.

"This means that the system in question could have planets with small orbits (like the earth's for example) orbiting that system's centre of mass despite the stars being many AUs away from it. It may be unlikely but it's certainly possible, right?" No, this does not mean that at all! An orbit asks for a centripetal force. In heliocentric systems this force is the gravity of the star (considering the gravity of the or…

..and if there were inhabitants, they'd be suffering unpredictable chaotic seasonality like the aliens in https://en.wikipedia.org/wiki/The_Three-Body_Problem

Could a planet maintain an atmosphere for any length of time under such variable attraction?

Re: Rare system of five stars discovered

#26

Post by zhte415 »

vacri wrote: post #10

Five-star systems aren't rare at all, in fact, they're problematically common. Usually the issue is that with such a limited array of choices, people gravitate to one star or five stars, and you don't get much meaningful information from the resulting scores. Percentage-based systems give more flexibility and have a wider 'active zone', without being overwhelmingly complex - and people are much less likely to given m…

So you're saying 5-star systems are just like a binary?

Re: Rare system of five stars discovered

#27

Post by hfsktr »

I have a question that a simple search didn't answer. Do astronomers actually measure the time it takes a star/planet/whatever to orbit? Or is it simply not possible for things after a certain distance?

For example how did they figure out that Pluto takes 247 Earth years per orbit? In our solar system I imagine they could measure it since it's close enough or see it in real time but even Pluto wasn't known for 248 years to see it go around.

With so many objects being so far away I thought it wouldn't really look like it moved from our perspective.

Re: Rare system of five stars discovered

#28

Post by patrickmclaren »

hfsktr wrote: post #27

I have a question that a simple search didn't answer. Do astronomers actually measure the time it takes a star/planet/whatever to orbit? Or is it simply not possible for things after a certain distance? For example how did they figure out that Pluto takes 247 Earth years per orbit? In our solar system I imagine they could measure it since it's close enough or see it in real time but even Pluto wasn't known for 248 ye…

Objects being far away doesn't necessarily mean that our view is slowed after adjusting for our speeds, albeit delayed.

Although I doubt much at this distance is measured optically, but rather using estimates of gravitational forces, perhaps through measuring various "wobbles" within the system.

- Not a physicist.

Re: Rare system of five stars discovered

#29

Post by lagadu »

restalis wrote: post #19
lagadu wrote: post #8

Ok, so objects orbit not other objects but rather centres of gravity. This means that the system in question could have planets with small orbits (like the earth's for example) orbiting that system's centre of mass despite the stars being many AUs away from it. It may be unlikely but it's certainly possible, right? Am I missing something that'd make this impossible? Because that would be incredibly cool! edit: I'm as…

"This means that the system in question could have planets with small orbits (like the earth's for example) orbiting that system's centre of mass despite the stars being many AUs away from it. It may be unlikely but it's certainly possible, right?" No, this does not mean that at all! An orbit asks for a centripetal force. In heliocentric systems this force is the gravity of the star (considering the gravity of the or…

Dammit, I knew it sounded way too cool to be possible :(

Thanks!

Re: Rare system of five stars discovered

#30

Post by Rexxar »

jeremysmyth wrote: post #11
nitrogen wrote: post #6

Earlier quoted context omitted.

> But what could they be orbiting around? >> a mutual centre of gravity The math of gravity is fascinating. Objects can orbit each other, with nothing in the middle.

You think that's good, try this: Objects can even orbit interesting points in space that are not themselves centers of gravity: https://en.wikipedia.org/wiki/Lagrangian_point

This is linked to orbit around Lagrangian points but it's more surprising: https://en.wikipedia.org/wiki/Horseshoe_orbit
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