Re: [math-fun] 7 earth-size planets identified in orbit around a dwarf star
Dan Asimov <asimov@msri.org> wrote:
Not just one, but seven Earth-size planets that could potentially harbor life have been identified orbiting a tiny star not too far away, offering the first realistic opportunity to search for biological signs of alien life outside of the solar system.
They're almost certainly tidally locked. It's an interesting question whether winds would keep the permanent dark side warm enough that the atmosphere, or at least any water vapor in it, wouldn't all freeze out there, making life impossible. As Stephen Baxter pointed out in his novel _Proxima_, set on a similar planet around Proxima Centauri, dwarf stars are projected to last trillions of years, not mere billions like our sun. (Interestingly, he just made up that planet, but it has since been discovered, like Jonathan Swift's two small moons of Mars.) Most stars that can be seen without a telescope have a very high intrinsic brightness, which means they last only millions of years, almost certainly not long enough for advanced life to evolve on planets around them. Getting back to math, Wikipedia says "The orbits of planets b-g are nearly in resonance, having ... nearest-neighbor period ratios (proceeding outward) of about 8/5, 5/3, 3/2, 3/2 and 4/3 ...." I'm sure everyone here recognizes the signifance of first three ratios.
Is there a theory that explains why 8:5 has a larger basin of attraction than 7:4, say? Jim Propp On Thursday, February 23, 2017, Keith F. Lynch <kfl@keithlynch.net> wrote:
Dan Asimov <asimov@msri.org <javascript:;>> wrote:
Not just one, but seven Earth-size planets that could potentially harbor life have been identified orbiting a tiny star not too far away, offering the first realistic opportunity to search for biological signs of alien life outside of the solar system.
They're almost certainly tidally locked. It's an interesting question whether winds would keep the permanent dark side warm enough that the atmosphere, or at least any water vapor in it, wouldn't all freeze out there, making life impossible.
As Stephen Baxter pointed out in his novel _Proxima_, set on a similar planet around Proxima Centauri, dwarf stars are projected to last trillions of years, not mere billions like our sun. (Interestingly, he just made up that planet, but it has since been discovered, like Jonathan Swift's two small moons of Mars.)
Most stars that can be seen without a telescope have a very high intrinsic brightness, which means they last only millions of years, almost certainly not long enough for advanced life to evolve on planets around them.
Getting back to math, Wikipedia says "The orbits of planets b-g are nearly in resonance, having ... nearest-neighbor period ratios (proceeding outward) of about 8/5, 5/3, 3/2, 3/2 and 4/3 ...." I'm sure everyone here recognizes the signifance of first three ratios.
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* James Propp <jamespropp@gmail.com> [Feb 24. 2017 08:05]:
Is there a theory that explains why 8:5 has a larger basin of attraction than 7:4, say?
Jim Propp
[...]
? contfrac(8/5) [1, 1, 1, 2] ? contfrac(7/4) [1, 1, 3] So at least 8/5 is closer to the most irrational value, (sqrt(5)+1)/2: ? contfrac((sqrt(5)+1)/2) [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...] To the cont-fractionists on this list: is the implied measure of irrationality by comparing simple continued fractions OK? Best regards, jj
Hello, is there a name for these 7 new planets ? funny : isn't there anybody that had the idea to name them after the 7 dwarfs ? That is : Doc, Grumpy, Happy, Sleepy, Dopey, Bashful, Sneezy ?? well, maybe it is not suitable for a planet's name. Any other inspired suggestions ? Best regards, Simon Plouffe Le 2017-02-25 à 18:57, Joerg Arndt a écrit :
* James Propp <jamespropp@gmail.com> [Feb 24. 2017 08:05]:
Is there a theory that explains why 8:5 has a larger basin of attraction than 7:4, say?
Jim Propp
[...] ? contfrac(8/5) [1, 1, 1, 2] ? contfrac(7/4) [1, 1, 3]
So at least 8/5 is closer to the most irrational value, (sqrt(5)+1)/2: ? contfrac((sqrt(5)+1)/2) [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...]
To the cont-fractionists on this list: is the implied measure of irrationality by comparing simple continued fractions OK?
Best regards, jj
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Yes, they're named TRAPPIST-1b, TRAPPIST-1c, TRAPPIST-1d, TRAPPIST-1e, TRAPPIST-1f, TRAPPIST-1G, and TRAPPIST-1h. Best wishes, Adam P. Goucher
Sent: Saturday, February 25, 2017 at 6:10 PM From: "Simon Plouffe" <simon.plouffe@gmail.com> To: math-fun@mailman.xmission.com Subject: Re: [math-fun] 7 earth-size planets identified in orbit around a dwarf star
Hello,
is there a name for these 7 new planets ?
funny : isn't there anybody that had the idea to name them after the 7 dwarfs ? That is : Doc, Grumpy, Happy, Sleepy, Dopey, Bashful, Sneezy ?? well, maybe it is not suitable for a planet's name.
Any other inspired suggestions ?
Best regards,
Simon Plouffe
Le 2017-02-25 à 18:57, Joerg Arndt a écrit :
* James Propp <jamespropp@gmail.com> [Feb 24. 2017 08:05]:
Is there a theory that explains why 8:5 has a larger basin of attraction than 7:4, say?
Jim Propp
[...] ? contfrac(8/5) [1, 1, 1, 2] ? contfrac(7/4) [1, 1, 3]
So at least 8/5 is closer to the most irrational value, (sqrt(5)+1)/2: ? contfrac((sqrt(5)+1)/2) [1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, ...]
To the cont-fractionists on this list: is the implied measure of irrationality by comparing simple continued fractions OK?
Best regards, jj
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participants (5)
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Adam P. Goucher -
James Propp -
Joerg Arndt -
Keith F. Lynch -
Simon Plouffe