What can I image in 5 minutes?

"Mark McIntyre" wrote in message
...
: Androcles wrote:
: "Mark McIntyre" wrote in message
: ...
: : Androcles wrote:
: : So the Seven Sisters is an optical septuplet?
: :
: : Yes.
:
: I should have added that this is commonly called an asterism, or, if
: large enough, a constellation.

Ah... astrology spam. Pictures in the fire, pictures in the clouds,
pictures in the stars. I was under the mistaken impression
that these were sci. newsgroups but maybe Kelleher is talking
to the right people after all.


: Then all stars are doubles. No matter which star you look at
: there is another within 30 arc seconds of it.
:
: Indeed. I guess the point is, how many appear single stars visually but
: resolve into a pair at moderate resolution?

Visually meaning less than 6th magnitude?
:
: From the Moon, yes. They must a be double city.
:
: Indeed. From the moon, London, Croydon and Slough would appear one city
: too. Thats kinda the point.

Bad example. Croydon is inside the M25, Slough outside on the M4.
http://apod.nasa.gov/apod/image/0304/london_iss_c1.jpg
Crawley would be seen before Slough and so would Dagenham,
even tiny Sheerness, they emit more light. Can't tell with Dartford,
it is under cloud cover in the image.

:
: Ok, and so is Bumf**k, Alabama.
:
: Childish.

That's the point. Double stars (and lists of) are a childish concept,
nothing more than astrology spam of no import or significance
whatsoever. Meaningless drivel to be given as much weight as
Kelleher's nonsense or any other crackpot's silly ideas.

"Mark McIntyre" wrote in message
...
: Androcles wrote:
:
: No binary but Sirius has ever "appeared close together".
:
: Nonsense.

Name just one, then.


:
:
: Yes, Sirius is a binary, 8 light years distant and a 50 year period.
: That makes it the only double by the dictionary definition, or else
: ALL stars are doubles since they all appear close to another somewhere.
:
: Gibberish.
I agree, "double" stars are nothing but gibberish.

:
: Absolutely NOT. The ONLY binary resolved in a telescope is
: Sirius and that only because A and B are well separated and the
: system is nearby.
:
: You now seem to be trolling. Into the bitbucket with you, my bucko..

I can't help your ignorance if you don't want to learn.

:
: : And no, this is NOT taken from wikipedia...
:
: I don't care where you got it, I'm not about to call Mars
: and Jupiter a double planet just because I've seen them
: "close together",
:
: On the other hand, if mars and jupiter remained visually close together
: for 100 years, what would you say?

I'd say
In hypothetical sentences introduced by 'if' and referring to
past time, where conditions are to be deemed 'unfulfilled',
the verb will regularly be found in the pluperfect subjunctive,
in both protasis and apodosis.
-- Donet, "Principles of Elementary Latin Syntax"

There is no "if", Mars and Jupiter have different orbits.
You now seem to be trolling. Into the bitbucket with you, my bucko..



: Assume you have no means of measuring
: their distance away (ie put yourself in the shoes of the astronomers who
: first catalogued doubles).

Be a troll, you mean?
No, I won't do that.


: so I'm asking what this strange fascination
: with "double" stars is and will continue to put "double" in
: quotation marks until supplied with a satisfactory answer.
:
: Allow me to put another word on quotes - "dork".

Oh, is that what you are.
**** off, dork.
*plonk*

In article ,
Mark McIntyre wrote:

(/are/ there any binary systems that can be resolved with the naked eye? )

*Any* binary system can be resolved by the naked eye if only viewed
from a close enough distance. :-)

As seen from the Earth, we have the Alfa Centauri system, where
Proxima Centauri resides some 3 degrees away from Alfa Centauri AB in
our sky. If only Proxima had been a more sun-like star rather than an
extremely faint red dwarf, then the Alfa Centauri system (AB)+C would have
been extremely easy to resolve with the naked eye.

Of course we also have Epsilon Lyrae, where the wide pair (AB)+(CD) resides
some 3 arc minutes from one another and can be resolved by people with
keen eyesight. Epsilon Lyrae is often used by skywatchers as a test of
their eyesight. And this is a physical pair, not an optical double.

The easier pair Alfa Capricorni, with the two components some 7 arc minutes
from one another, is an optical pair though.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

In article ,
Mark McIntyre wrote:
Androcles wrote:

I don't care where you got it, I'm not about to call Mars
and Jupiter a double planet just because I've seen them
"close together",

On the other hand, if mars and jupiter remained visually close together
for 100 years, what would you say? Assume you have no means of measuring
their distance away (ie put yourself in the shoes of the astronomers who
first catalogued doubles).

"for 100 years" is asking far too much! After all, that's some 8
times the orbital period of Jupiter or some 55 times the orbital
period of Mars.

As a comparison, 100 years is only one 2.5-millionth of the typical
orbital period of most stars we can see in our sky with modest optical
aid. And if we divide the orbital period of Jupiter with 2.5 million,
we get the very short time span of 2.5 minutes. And if two bright
planets are in a close conjunction, they will remain so for much
longer than 2.5 minutes, and during that time span, we do have an
apparent "double planet" in our sky. Most people would probably refer
to it as a "double star" though, since most people are unable to
distinguish a star from a planet in the sky.

Quite naturally, when enough time (thousands of years) have passed for
the two components of an optical double star to drift well away from
one another, the observers of that time will no longer refer to it as
an optical double star.

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

Paul Schlyter wrote:
In article ,
Mark McIntyre wrote:
Androcles wrote:

I don't care where you got it, I'm not about to call Mars
and Jupiter a double planet just because I've seen them
"close together",
On the other hand, if mars and jupiter remained visually close together
for 100 years, what would you say? Assume you have no means of measuring
their distance away (ie put yourself in the shoes of the astronomers who
first catalogued doubles).

"for 100 years" is asking far too much! After all, that's some 8
times the orbital period of Jupiter or some 55 times the orbital
period of Mars.

Thats my point - Jupiter and Mars don't give the *appearance* of being
close together for more than a few days.


Quite naturally, when enough time (thousands of years) have passed for
the two components of an optical double star to drift well away from
one another, the observers of that time will no longer refer to it as
an optical double star.



--
Mark McIntyre

CLC FAQ http://c-faq.com/
CLC readme: http://www.ungerhu.com/jxh/clc.welcome.txt

"Paul Schlyter" wrote in message
...
: In article ,
: Mark McIntyre wrote:
:
: (/are/ there any binary systems that can be resolved with the naked
eye? )
:
: *Any* binary system can be resolved by the naked eye if only viewed
: from a close enough distance. :-)

If it IS a binary, sure.


:
: As seen from the Earth, we have the Alfa Centauri system, where
: Proxima Centauri resides some 3 degrees away from Alfa Centauri AB in
: our sky.

Widely separated and nearby. I admit I overlooked that system.


If only Proxima had been a more sun-like star rather than an
: extremely faint red dwarf, then the Alfa Centauri system (AB)+C would have
: been extremely easy to resolve with the naked eye.
:
: Of course we also have Epsilon Lyrae, where the wide pair (AB)+(CD)
resides
: some 3 arc minutes from one another and can be resolved by people with
: keen eyesight.
Epsilon Lyrae is often used by skywatchers as a test of
: their eyesight. And this is a physical pair, not an optical double.

Widely separated and nearby. Period?

:
: The easier pair Alfa Capricorni, with the two components some 7 arc
minutes
: from one another, is an optical pair though.

And so of no significance other than serendipity.
Oh look, here are two stars only 7 arc minutes apart, it must be an
optical double.
Oh look, here is the sun. It must be daytime.

In article ,
Androcles wrote:

"Paul Schlyter" wrote in message
...
: In article ,
: Mark McIntyre wrote:
:
: (/are/ there any binary systems that can be resolved with the naked
eye? )
:
: *Any* binary system can be resolved by the naked eye if only viewed
: from a close enough distance. :-)

If it IS a binary, sure.

:-) ...can you name even one binary system which isn't binary? g


: As seen from the Earth, we have the Alfa Centauri system, where
: Proxima Centauri resides some 3 degrees away from Alfa Centauri AB in
: our sky.

Widely separated and nearby. I admit I overlooked that system.

If only Proxima had been a more sun-like star rather than an
: extremely faint red dwarf, then the Alfa Centauri system (AB)+C would have
: been extremely easy to resolve with the naked eye.
:
: Of course we also have Epsilon Lyrae, where the wide pair (AB)+(CD)
resides
: some 3 arc minutes from one another and can be resolved by people with
: keen eyesight.
Epsilon Lyrae is often used by skywatchers as a test of
: their eyesight. And this is a physical pair, not an optical double.

Widely separated and nearby. Period?

That period is unknown but must be very long: at least hundreds of thousands
of years, probably more. So far, no relative motion has been detected in that
wide pair. Even the two narrow pairs of Epsilon Lyrae each have an orbital
period of the order of a thousand years.

: The easier pair Alfa Capricorni, with the two components some 7 arc
minutes
: from one another, is an optical pair though.

And so of no significance other than serendipity.
Oh look, here are two stars only 7 arc minutes apart, it must be an
optical double.
Oh look, here is the sun. It must be daytime.

You can use Epsilon Lyrae and Alfa Capricorni as two good examples of
how to distinguish an optical pair from a physical pair: the relative motion
in the wide pair of Epsilon Lyrae is too small to be detectable for us,
but in Alfa Capricorni the relative motion is quite obvious.




--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

"Paul Schlyter" wrote in message
...
: In article ,
: Androcles wrote:
:
: "Paul Schlyter" wrote in message
: ...
: : In article ,
: : Mark McIntyre wrote:
: :
: : (/are/ there any binary systems that can be resolved with the naked
: eye? )
: :
: : *Any* binary system can be resolved by the naked eye if only viewed
: : from a close enough distance. :-)
:
: If it IS a binary, sure.
:
::-) ...can you name even one binary system which isn't binary? g

Oddly and amusingly as it may seem to you, yes.
A binary system is only a binary if
a) it has two stars.
b) the stars are orbiting a common barycentre.
c) it can be resolved into two stars OR the velocity
of at least one of the pair can be measured spectroscopically.
The wild conjecture of an 18-year-old kid isn't sufficient
evidence for finding a binary system.
Do you agree?

:
: : As seen from the Earth, we have the Alfa Centauri system, where
: : Proxima Centauri resides some 3 degrees away from Alfa Centauri AB in
: : our sky.
:
: Widely separated and nearby. I admit I overlooked that system.
:
: If only Proxima had been a more sun-like star rather than an
: : extremely faint red dwarf, then the Alfa Centauri system (AB)+C would
have
: : been extremely easy to resolve with the naked eye.
: :
: : Of course we also have Epsilon Lyrae, where the wide pair (AB)+(CD)
: resides
: : some 3 arc minutes from one another and can be resolved by people with
: : keen eyesight.
: Epsilon Lyrae is often used by skywatchers as a test of
: : their eyesight. And this is a physical pair, not an optical double.
:
: Widely separated and nearby. Period?
:
: That period is unknown but must be very long: at least hundreds of
thousands
: of years, probably more. So far, no relative motion has been detected in
that
: wide pair. Even the two narrow pairs of Epsilon Lyrae each have an
orbital
: period of the order of a thousand years.

Ok, so it is mere serendipity, there is nothing special about the stars
or about their relationship, the only link is a line of three points the
observer happens to be on. It would be strange indeed if such
a relation did NOT exist given the vast number of stars available.

:
: : The easier pair Alfa Capricorni, with the two components some 7 arc
: minutes
: : from one another, is an optical pair though.
:
: And so of no significance other than serendipity.
: Oh look, here are two stars only 7 arc minutes apart, it must be an
: optical double.
: Oh look, here is the sun. It must be daytime.
:
: You can use Epsilon Lyrae and Alfa Capricorni as two good examples of
: how to distinguish an optical pair from a physical pair: the relative
motion
: in the wide pair of Epsilon Lyrae is too small to be detectable for us,
: but in Alfa Capricorni the relative motion is quite obvious.

Part of my original post was to point out that optical pairs are of
no particular interest to science. Where there is relative motion we
have reason to investigate a relationship, and the closer the pair are
the faster that motion will be. If you have no motion then it is unlikely
that you have a binary. Of course you could be looking at the
plane of the orbit face-on, but if the system is eclipsing then
you have to be looking at it edge-on or nearly so and the motion
easily detectable, particularly if the so-called binary has a short
period measured in hours rather than years.

In article ,
Androcles wrote:

"Paul Schlyter" wrote in message
...
: In article ,
: Androcles wrote:
:
: "Paul Schlyter" wrote in message
: ...
: : In article ,
: : Mark McIntyre wrote:
: :
: : (/are/ there any binary systems that can be resolved with the naked
: eye? )
: :
: : *Any* binary system can be resolved by the naked eye if only viewed
: : from a close enough distance. :-)
:
: If it IS a binary, sure.
:
::-) ...can you name even one binary system which isn't binary? g

Oddly and amusingly as it may seem to you, yes.
A binary system is only a binary if
a) it has two stars.
b) the stars are orbiting a common barycentre.
c) it can be resolved into two stars OR the velocity
of at least one of the pair can be measured spectroscopically.
The wild conjecture of an 18-year-old kid isn't sufficient
evidence for finding a binary system.
Do you agree?

If the system isn't a binary, then the question whether it's a binary
or not has already been answered. There are no binary non-binaries,
don't you agree?

: : Of course we also have Epsilon Lyrae, where the wide pair (AB)+(CD)
: resides
: : some 3 arc minutes from one another and can be resolved by people with
: : keen eyesight.
: Epsilon Lyrae is often used by skywatchers as a test of
: : their eyesight. And this is a physical pair, not an optical double.
:
: Widely separated and nearby. Period?
:
: That period is unknown but must be very long: at least hundreds of
: thousands of years, probably more. So far, no relative motion has
: been detected in that wide pair. Even the two narrow pairs of Epsilon
: Lyrae each have an orbital period of the order of a thousand years.

Ok, so it is mere serendipity, there is nothing special about the stars
or about their relationship, the only link is a line of three points the
observer happens to be on. It would be strange indeed if such
a relation did NOT exist given the vast number of stars available.

You're overlooking a few things here....

An optical pair, where the two unrelated stars just happen to be nearly
along the same line of sight as seen from us, will almost certainly have
both different distances and different proper motions. Which means the
two stars will have different parallaxes as well as, relative to one
another, a quite noticeable motion.

The two pairs of Epsilon Lyrae are both, as far as we can tell, at the
same distance. They also share the same proper motion relative to
the background of fainter stars. It is extremely unlikely that this
is due to serendipity - it's vastly more likely that it's because the
two pairs are gravitationally bound to one another.

You accepted that Proxima Centauri is a physical member of the Alfa
Centauri system, even though it resides 3 degrees away from the
Alfa Centauri A+B pair. The reason Proxima is considered a physical
member of this system is that it resides at nearly the same distance
(in this case somewhat closer: 4.2 ly compared to 4.3 ly for the A+B
pair) *and* that Proxima shares the proper motion of the A+B pair.
If Proxima would have a quite different proper motion compared to
the Alfa Centauri A+B pair, then Proxima's velocity relative to
the A+B pair would exced the escape velocity, and Proxima would then
not be a physical member of that system, but merely a star which happened
to pass by.

So the absence of detectable relative motion of the two pairs in
Epsilon Lyrae is a clear indication that the two pairs *are*
gravitationally bound to one another, since the relative velocity
then does not exceed the velocity of escape. Two stars passing
near one another by chance almost always do so with a relative
velocity much larger than some fraction of a kilometer per second.
And if they initially happened to be very far apart *and* almost at
rest relative to one another, then they would never get close to one
another - right?


: : The easier pair Alfa Capricorni, with the two components some 7 arc
: minutes
: : from one another, is an optical pair though.
:
: And so of no significance other than serendipity.
: Oh look, here are two stars only 7 arc minutes apart, it must be an
: optical double.
: Oh look, here is the sun. It must be daytime.
:
: You can use Epsilon Lyrae and Alfa Capricorni as two good examples of
: how to distinguish an optical pair from a physical pair: the relative
motion
: in the wide pair of Epsilon Lyrae is too small to be detectable for us,
: but in Alfa Capricorni the relative motion is quite obvious.

Part of my original post was to point out that optical pairs are of
no particular interest to science. Where there is relative motion we
have reason to investigate a relationship, and the closer the pair are
the faster that motion will be. If you have no motion then it is unlikely
that you have a binary.

I strongly disagree with you here. A very wide binary with a period
of a million years or so will have undetectable motion to us at our
present state of astrometric measurements. In time we will of course
also be able to detect also the very slow relative motion of these pairs,
but we're not there yet.

A very wide pair with an easily detectable relative motion will not be
a binary, for one simple reason: even if the stars are close to one
another in space, their relative velocities will exceed their mutual
excape velocity. Therefore, after their close encounter they will
wander away from one another into space, and not orbit one another in
a closed orbit.

A close binary will of course have a fast motion, here we agree. But
we were discussing wide pairs he binaries resolvable with the naked
eye. That excludes close binaries.

Of course you could be looking at the
plane of the orbit face-on, but if the system is eclipsing then
you have to be looking at it edge-on or nearly so and the motion
easily detectable, particularly if the so-called binary has a short
period measured in hours rather than years.

.....and such a binary won't be resolvab with the naked eye either....

--
----------------------------------------------------------------
Paul Schlyter, Grev Turegatan 40, SE-114 38 Stockholm, SWEDEN
e-mail: pausch at stockholm dot bostream dot se
WWW: http://stjarnhimlen.se/

In article ,
Androcles wrote:
Meaningless drivel to be given as much weight as
Kelleher's nonsense or any other crackpot's silly ideas.

Mr Pot, meet Mr Kettle.

-- Richard
--
:wq