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Procyon
2005-Apr-14, 11:43 AM
hey guys this is my first post!

"Science has at last discovered that the Sun is not a dead centre, with planets and comets wheeling around it but itself stationary. It is now ascertained that the Sun is also in motion, around some other and vastly mightier centre. Astronomers are not
fully agreed as to what or where that centre is."

i read that last night and wondered.... do we have an answer for this today? i suppose it's not the centre of the milky way?

Timing
2005-Apr-14, 12:05 PM
Procyon,

From different sources I learned that our Solar system cycles around Alcyone, a central Star in the Pleiades. It takes around 25.920 years for our Sun to cycle around Alcyone. Alcyone itself cycles around the Centre of our Universe in around 259.200 years.
If this is what you're asking for..... let me know

Timing
2005-Apr-14, 12:11 PM
now I'm registered....

Procyon
2005-Apr-14, 12:20 PM
I take it Alcyone is one bigass star!

John L
2005-Apr-14, 02:28 PM
Actually the sun does orbit around the center of the Milky Way galaxy about every 220 million years. The sun does not orbit any other stars, and as there is no center of the universe I can't imagine how the sun could orbit it every 259 years. Where did you get those figures, Timing?

Timing
2005-Apr-14, 02:36 PM
Did some calculations:
Distance between Sun and Alcyone is 365 lightyears,
Means 3453192 bln km,
Means a Cycle around Alcyone takes 21697045,24 bln km,

Means the Sun should have to move 26543,55 km's per second to be able to cycle around Alcyone in 21.960. This is rather fast I would say.

You can find a lot of assumptions on Alcyone being a Central Star but I must admit that after doing these calculations....

Anyway, is there anyone sharing the idea of a spinning universe with inside it, a spinning solar system and who has some facts or theories?

GOURDHEAD
2005-Apr-14, 06:57 PM
In addition to orbiting the center of the MW, the sun sinusoidally moves within the MW's disk in cycles with periods of approximately 26 million years. Looks like about ten of these every "galactic year". How have we assured ourselves that the sun is not gravitationally locked with some other stars orbiting a common center as the group orbits the MW center? The gravitational properties of the disk seems to herd the disk stars to stay within the confines of the disk, although I read some time ago that Arcturus' orbit intersects the sun's orbit at an appreciable angle. Is it considered to be a disk star or just out of synchronicity with the sun's motion?

antoniseb
2005-Apr-14, 08:00 PM
Originally posted by GOURDHEAD@Apr 14 2005, 06:57 PM
How have we assured ourselves that the sun is not gravitationally locked with some other stars orbiting a common center as the group orbits the MW center?
For one thing, take a look at the gravitational force that an object with a few solar masses has on the sun at a distance of fifty light years. Nothing is locked.

Shoemoodoshaloo
2005-Apr-14, 11:49 PM
As far as I can add, there are two things the sun orbits. One is the center of the solarsystem. Since gravity is a force between the planets and the sun, the planets are tugged inward and the sun is tugged outward. So the sun does rotate around the center of the solarsystem, but it's probably such a small rotation that the sun seems like it's wobbling.

The sun orbit the milky was every 220 million years I think. It was stated before in a previous post. If you know the equation of G, you'd know that if another star was 50 million light years, then you take that distance squared and get a huge number that makes the force of gravity very small. As stated before, "Nothing is locked".

GOURDHEAD
2005-Apr-15, 06:21 PM
For one thing, take a look at the gravitational force that an object with a few solar masses has on the sun at a distance of fifty light years. Nothing is locked. Agreed with respect to the 50 light year object, but there are objects much closer and not necessarily seen. I have assumed that the closed globular clusters of stars are gravitationally locked as a group and revolve about a common center as they orbit the MW thus allowing their individual paths through the MW to describe a fanciful set of epicycles.

If we take 12 billion years as the age of the MW, and approximately 0.25 billion years as the sun's galactic year, the sun or what became incorporated into it has made approximately 50 trips around the galaxy. As this stuff cycles through the latitudinal center of the MWs disk, there should be a damping to the latitudinal displacement over time. Since the sun cycles through the disk about 10 times each revolution, there have been approximately 500 such cycles. Does anyone know how the amplitude of the disk cycling has changed over time?

alainprice
2005-Apr-15, 09:54 PM
If the sun were free falling around the milky way's supermassive BH, would it not easily orbit any object? Even being locked in a galactic orbit, the sun can still orbit another star cluster, no matter how small the force may be.
However, due to the sheer number of gravitational influences, it's much easier to find a stable orbit for the sun and call it a day.

Wasn't it previously stated that the sun crosses the galactic plane regularly? If that is so, it either crosses it twice per orbit around the BH, or crosses more frequently. For it to cross the galactic plane more than that, would it not be logical to assume the sun is orbiting an object within 100 LY of us?

djkma
2005-Apr-16, 12:42 AM
I find it interesting that someone believes we are in orbit around another massive star. Don't you think we would have noticed the patterns of the stars relative to us to properly discern this? I believe we are going up and down through the disk of the MW, but I don't know how long this takes. Is this starting the proposal that there is a massive star in the disk and we are going around it. Anyways, Come on Ice Age. I bet the meteor showers kick butt. Is there a pattern of high levels of impacts from meteors, and if so what is the timing?

TheThorn
2005-Apr-16, 12:49 AM
Originally posted by GOURDHEAD@Apr 14 2005, 06:57 PM
I read some time ago that Arcturus' orbit intersects the sun's orbit at an appreciable angle. Is it considered to be a disk star or just out of synchronicity with the sun's motion?
Arcturus is a very interesting star, one of my favourites. It's a "thick disk" star. It travels a couple of thousand ly above and below the disk, and is just passing by at the moment. A half-million years ago it wasn't visible to the naked eye, is nearing its closest approach to us in the next thousand years or so, and a half million years from now it will be invisible to the naked eye again.

There are at least 53 other stars in the area that have similar motion called the "Arcturus Group". Their orbits are highly elliptical as well as inclined. Some scientists have speculated that they may be left overs from a small galaxy that the Milky Way canibalized several billion years ago.

It's even interesting just as a star. It's about the same mass as the sun, but over 200 times as bright, because it has left the main sequence, which means it's a lot older than the sun. It's "burning" helium at the moment, so it's nearing the end of it's life.

http://www.solstation.com/stars2/arcturus.htm

MACHO
2005-Apr-16, 10:39 AM
ha.Mr.timing .If the sun moved at such a speed then it would be gravitationally distorted and a mass greater than a blackhole.food for thought. :lol: :P

Mr. Smartypants gamer guy
2005-Apr-16, 10:10 PM
yea, and very very few ideas come to mind of things that could ever have more gravity than a blk hole...

Guest
2005-Apr-18, 12:04 PM
there are many mysteries of matter man cannot imagine,he is reaching to the limit of knowledge ,but he never handles it.

qraal
2005-Apr-19, 03:44 AM
Hi All

The Sun orbits the Galactic Centre which is some ~ 26,000 light years away, and the core Black Hole is pretty close to the centre itself. While it masses 3 million or so times the mass of the Sun it's not quite true to say that we're held in our orbit by its gravity - in fact all of the mass interior to the Sun's orbit keeps it in place and in motion in a vast wobbly ellipse. The total mass required is pretty easy to figure out by w = sqrt(G*M/R^3), with w = 2*pi/T, with a T of 225 million years and an R of ~ 26,000 ly (2.46 x 10^20 metres), the mass within is ~ 88 billion solar masses. Oddly enough it's mostly not the disk of the Galaxy we see, but is mostly unseen Dark Matter distributed spherically about the Core.

Incidentally the Sun's Hill Sphere - the zone in which it exclusively controls an object's motion - is roughly ~ 1.1 light years in radius. Beyond that and the Galaxy's gravity becomes dominant. The Sun-Galaxy Lagrange 1 & 2 points are roughly 9.9 light years away on the Sun-Galaxy vector.

qraal

PS Black Hole gravity is no bigger than any other object of the same mass, but black hole mass is packed in a space much, much smaller. Close to the object the field is much "denser" than in any other comparable mass - what matters to anyone close by is field strength not the total field.

gavwvin
2005-Apr-19, 07:35 AM
Distance between Sun and Alcyone is 365 lightyears,
Means 3453192 bln km,
Means a Cycle around Alcyone takes 21697045,24 bln km,

the formula for calculating time period / distance / mass (T squared = 4 pi squared r cubed over GM) is based on the assumption that the smaller mass is actually in orbit- you can't calculate time period just because you have two objects with mass and distance between them. If that were the case I could calculate my time period of orbit around you, as we both have a mass and there's a distance between us.

eburacum45
2005-Apr-19, 08:23 PM
We are actually orbiting the entire mass of the Galaxy, including the black hole at the centre and all the stars, interstellar dust and gas, smaller black holes and neutron stars; and perhaps most importantly of all- the invisible dark matter in our galaxy (at least all that dark matter interior to our orbit)...

alainprice
2005-Apr-19, 10:51 PM
Black hole originators are more massive than black holes.

Imagine the sun were doomed to become a BH. Right before it does, it will shed some material, and then collapse. It has no more gravity as a black hole than it did as a star. It's actually weaker as a black hole, having lost mass.