Magellanic Clouds question

Ron Miller wrote:

I think I may have answered my own question. If I know that the orbit of the
two clouds is nearly circular and more or less centered on the center of the
Milky Way, and I know what the position of the clouds is in relation to the
galaxy, then I know how much the orbit is tilted... Right?

Not in principle, from their position alone. An infinite number of
circles will meet the two requirements of having their centre in
common with the Galaxy and of passing through a given Cloud. Without
further constraints the problem is like asking "What is the longitude
of the North Pole?"

Radial-velocity data for the Clouds would narrow the possibilities --
but I don't think one can exclude eccentric orbits from
consideration. An abstract from the AAS _Bulletin_ at

http://www.aas.org/publications/baas/v25n4/aas183/abs/S10808.html

suggests that the Clouds were only recently captured (having been
near M31 some 10 Gya) and are only on their second near passage
(periapsis?) to our Galaxy. Such an orbit seems unlikely to be
circular. But the Local Group taken overall seems to lie mainly near
a plane whose pole is somewhere around Castor & Pollux, inclined
perhaps 60° to the Milky Way. Assuming the Clouds' orbit to be more
or less in the same plane would narrow the possibilities, implying a
motion in the approximate direction of Virgo.

If we assume the "Magellanic Stream" to be in effect the Clouds'
trail, having positional data for a few points along it would be very
helpful in fixing the plane of their orbit. See

http://www.macalester.edu/astronomy/research/alyson/stream2.html.

(I hadn't heard of this object -- or series of objects -- before today.)

The following abstract -- or at least some of its cited references --
might be helpful, if you have a PostScript printer or viewer:

http://cadcwww.dao.nrc.ca/iau190/manuscripts/sawatakeyasu.ps.

--
Odysseus

I'm not so sure :-( Looking at it again, l and b were defined in the
text (doh!) but what you need is not where they are now, which is simply
a matter of co-ordinate conversion, but the latitude and longitude where
the orbit crosses the galactic plane. And just how accurate is that "at
right angles" ?

In message , Ron Miller
writes

Excellent! I'll check this over...it looks like just what I need.

Thanks,
R

I've been able to find a reference to the orbit being circular, and
several references say the orbit is at right angles to the plane of the
Galaxy.
Bingo - I think.
http://www-hpcc.astro.washington.edu...ore/stream/str
eam.html gives "l" and "b" for the LMC and SMC

l b
LMC 280 -33
SMC 303 -44

--
"It is written in mathematical language"
Remove spam and invalid from address to reply.

I'm not so sure :-( Looking at it again, l and b were defined in the
text (doh!) but what you need is not where they are now, which is simply
a matter of co-ordinate conversion, but the latitude and longitude where
the orbit crosses the galactic plane. And just how accurate is that "at
right angles" ?

In message , Ron Miller
writes

Excellent! I'll check this over...it looks like just what I need.

Thanks,
R

I've been able to find a reference to the orbit being circular, and
several references say the orbit is at right angles to the plane of the
Galaxy.
Bingo - I think.
http://www-hpcc.astro.washington.edu...ore/stream/str
eam.html gives "l" and "b" for the LMC and SMC

l b
LMC 280 -33
SMC 303 -44

--
"It is written in mathematical language"
Remove spam and invalid from address to reply.

Jonathan Silverlight
wrote in :

In message , Ron Miller
writes

"Ron Miller" wrote in message
...
I'm working on an illustration of the Milky Galaxy seen from some
considerable distance away. I have the relative positions of the LMC
and SMC, but I need to know what their orbits are relative to the
plane of the galaxy. That is, how much are their orbits tipped to
the plane?

Thanks in advance,
RM

I think I may have answered my own question. If I know that the orbit
of the two clouds is nearly circular and more or less centered on the
center of the Milky Way, and I know what the position of the clouds is
in relation to the galaxy, then I know how much the orbit is tilted...
Right?

I've been able to find a reference to the orbit being circular, and
several references say the orbit is at right angles to the plane of
the Galaxy.
Bingo - I think.
http://www-hpcc.astro.washington.edu...moore/stream/s
tr eam.html gives "l" and "b" for the LMC and SMC

l b
LMC 280 -33
SMC 303 -44

What are l and b, and how did people find things out before the
Internet was invented? ;-)

Confirmed with pre-internet Norton's Star Atlas (17th Ed), Map 18 Galactic
Chart!

Martin Lewicki

Jonathan Silverlight
wrote in :

In message , Ron Miller
writes

"Ron Miller" wrote in message
...
I'm working on an illustration of the Milky Galaxy seen from some
considerable distance away. I have the relative positions of the LMC
and SMC, but I need to know what their orbits are relative to the
plane of the galaxy. That is, how much are their orbits tipped to
the plane?

Thanks in advance,
RM

I think I may have answered my own question. If I know that the orbit
of the two clouds is nearly circular and more or less centered on the
center of the Milky Way, and I know what the position of the clouds is
in relation to the galaxy, then I know how much the orbit is tilted...
Right?

I've been able to find a reference to the orbit being circular, and
several references say the orbit is at right angles to the plane of
the Galaxy.
Bingo - I think.
http://www-hpcc.astro.washington.edu...moore/stream/s
tr eam.html gives "l" and "b" for the LMC and SMC

l b
LMC 280 -33
SMC 303 -44

What are l and b, and how did people find things out before the
Internet was invented? ;-)

Confirmed with pre-internet Norton's Star Atlas (17th Ed), Map 18 Galactic
Chart!

Martin Lewicki

Ron Miller wrote:
I'm working on an illustration of the Milky Galaxy seen from some
considerable distance away. I have the relative positions of the LMC and
SMC, but I need to know what their orbits are relative to the plane of the
galaxy. That is, how much are their orbits tipped to the plane?

Thanks in advance,
RM



Check out the November Astronomy magazine (pages 41-42). All you ever
wanted to know about the LG.

lightshow

Ron Miller wrote:
I'm working on an illustration of the Milky Galaxy seen from some
considerable distance away. I have the relative positions of the LMC and
SMC, but I need to know what their orbits are relative to the plane of the
galaxy. That is, how much are their orbits tipped to the plane?

Thanks in advance,
RM



Check out the November Astronomy magazine (pages 41-42). All you ever
wanted to know about the LG.

lightshow

Thanks to all for the advice. When the illustration is done, I'll post it
where everyone can view it if they wish.

R

Thanks to all for the advice. When the illustration is done, I'll post it
where everyone can view it if they wish.

R