Binary system


by Phy_enthusiast
Tags: binary
Phy_enthusiast
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#1
Sep22-13, 04:38 AM
P: 20
which is the first binary star system discovered ever?
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Drakkith
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#2
Sep22-13, 04:48 AM
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According to wiki it's Xi Ursae Majoris.

http://en.wikipedia.org/wiki/Xi_Ursae_Majoris
Phy_enthusiast
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#3
Sep23-13, 03:42 AM
P: 20
ok.but is it the first ever known to man???

Drakkith
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#4
Sep23-13, 03:56 AM
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Binary system


Per wiki:

Xi Ursae Majoris (Xi UMa, ξ Ursae Majoris, ξ UMa) is a star system in the constellation Ursa Major. On May 2, 1780, Sir William Herschel discovered that this was a binary star system, making it the first such system ever discovered.
I'd say that's a yes.
Phy_enthusiast
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#5
Sep23-13, 04:07 AM
P: 20
but there are ancient records that people identified some stars to be binary....even before gravity was discovered.
Drakkith
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#6
Sep23-13, 05:13 AM
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Quote Quote by Phy_enthusiast View Post
but there are ancient records that people identified some stars to be binary....even before gravity was discovered.
Those are visual binaries. Some of them have turned out to be real binary stars, but no one actually knew about gravitationally bound binary stars until 1780.
Vanadium 50
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#7
Sep23-13, 05:20 AM
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Quote Quote by Phy_enthusiast View Post
but there are ancient records that people identified some stars to be binary....even before gravity was discovered.
Please provide references for this. Especially if you are going to claim the answer you got was wrong.
snorkack
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#8
Sep23-13, 05:53 AM
P: 358
Consider the other easy binaries...
from
http://www.ianridpath.com/binaries.htm
Xi UMa/Alula Australis - semimajor separation 2,5创, period 60 years, magnitudes 4,3/4,8
for comparison:
Eta Cas - 12创, 480y, 3,5/7,4
Alpha For - 4,0创, 269y, 4,0/7,2
Castor - 6,8创, 467y, 1,9/3,0
Gamma Leo - 4,2创, 510y, 2,4/3,6
Gamma Vir - 3,6创, 169y, 3,5/3,5
Toliman - 7,6创, 80y, 0,0/1,3
Xi Boo - 4,9创, 152y, 4,8/7,0
44 Boo - 3,7创, 210y, 4,8/6
70 Oph - 4,5创, 88y, 4,2/6,2
61 Cygni - 24,3创, 678y, 5,4/6,1
Zeta Aquarii - 3,4创, 487y, 4,3/4,5

It is odd that Alula Australis should have been the first... compared to say 70 Ophiuchi and especially Toliman.
Phy_enthusiast
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#9
Sep23-13, 06:40 AM
P: 20
from ancient times it is known in indian astronomy that two stars mizar and alcor is a binary system in big dipper asterism.
Phy_enthusiast
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#10
Sep23-13, 06:42 AM
P: 20
it is probably the most ancient and first of its kind discovered in sky by early astronomers
Drakkith
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#11
Sep23-13, 06:45 AM
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Quote Quote by Phy_enthusiast View Post
from ancient times it is known in indian astronomy that two stars mizar and alcor is a binary system in big dipper asterism.
Quote Quote by Phy_enthusiast View Post
it is probably the most ancient and first of its kind discovered in sky by early astronomers
Yes, but they didn't know it was an actual binary star at the time. And by "actual" I mean two stars gravitationally bound to each other.
Phy_enthusiast
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#12
Sep23-13, 06:53 AM
P: 20
It is mentioned in indian texts that one of the star moves ahead of other over certain period of time and then the first one moves ahead of second one.this obserbvation of movement clearly indicates first sign of astronomical phenomenon of binary star.
Phy_enthusiast
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#13
Sep23-13, 06:55 AM
P: 20
This observation was made over a course of many centuries in indian astronomy.
Drakkith
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#14
Sep23-13, 07:12 AM
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Mind giving a reference?
Phy_enthusiast
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#15
Sep23-13, 07:41 AM
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You can search for Vashistha and arundhati on internet.These are the ancient indian name for Mizar and alcor.
Drakkith
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#16
Sep23-13, 01:57 PM
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Throwing them into an orbital period calculator gives me an orbital period of approximately 10 million years. Assuming I'm within even an order of magnitude, it seems unlikely that ancient indians could know they moved with each other. The time scale is simply too long. Even over 5,000 years their orbital motion would not be able to be seen.
jim mcnamara
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#17
Sep23-13, 06:30 PM
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A reference is not a "google search" for two star names. Please. We want real references here. Do you know what that means? An article written by an expert astronomer, could be a hundred years old. Observations you mention were made visually a long time ago and cannot be verified as an observation of a real gravity-bound system.

This seems like a rhetorical post to me. You assume you already know the answer, and it appears that you do not.

Thanks.
Phy_enthusiast
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#18
Sep25-13, 03:21 AM
P: 20
I dont know the answer, i suggested alcor and mizar because it was observed before william herschel discovered other binaries.I think they were first visual binaries ever discovered.But there proper motion was also studied by ancient indians.


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