Dual Suns

[Helio]

Yes, the radial velocity (RV) in the first (left) table gives the measured velocities, so they are the actual velocities towards (neg.) or away (+) from, us, in kps.

The second table shows what happens if we remove our assumption that the expansion rate is included in the first table. This requires, of course, reducing the radial velocity by 70 kps (it may prove a little less someday) but this is per million parsecs (3.26 million lyrs), so for, say, half that distance, only 35kps would be reduced, thus distance must be part of the calculation.

I used a scatter graph, which doesn't require one to sort by distance before plotting.

I look forward to the likely nicer graph you are considering.

Note that the table has only about 1/2 of the actual number of galaxies in our Local Group, so there may be more data out there that would improve the results.

 

[Catastrophe]

OK, thanks Helio.

I have a rough graph using one of the others, but now I will try to produce a nice, tidy one using the radial velocity.

Cat

 

[Catastrophe]

OK. I have a rough graph ready for redrawing. Just one thing - what are the units of radial velocity? Are they czB?

Cat :

 

[Helio]

OK. I have a rough graph ready for redrawing. Just one thing - what are the units of radial velocity? Are they czB?

kps (km/sec).

 

[Catastrophe]

Helio, Thanks. What was all this stuff about czB anyway?

Cat

 

[Catastrophe]

https://imgur.com/a/orzeEMj

View: https://imgur.com/a/orzeEMj

 

[Catastrophe]

OK. Here is the graph of speed km/sec vs distance megaparsecs.
I have added the "Hubble" line from zero (as they do) slope 73.8 (latest figure I found. Slight difference won't affect the picture too much.

Thanks to Helio for providing the data.

There are two interesting points, as I see it.
1) You have the "Hubble line) showing some galaxies following "Hubbles law" albeit very approximately.
2) you have (in red) those galaxies which seem to show only connection with distance. This seems reasonable for a "local group".

However, it should be pointed out that some of the "Hubble line" points are also present on the "distance" connection.

My suggestion is that, at low distances, the "Hubble line" breaks down, and proximity (gravity) takes over. Distance is limited (Local Group) but velocities (positive or negative) can vary widely.

If Helio would kindly consider providing more data, I will willingly add it to the graph.

Any comments welcomed.

Cat

 

[Catastrophe]

Having 'slept on it' (I am in UK), there are a few other points I can mention.

The value oh Hubble constant I used seemed a little high, I have Googled again and got:

The most recent precise measurements of the distances and movements of distant, exploding stars suggest a Hubble constant of 69.8 km/s/Mpc, but other reports have pushed the value as high as 74 km/s/Mpc.

Actually it makes very little difference on the graph. The line goes through zero origin (Hubble's Law). If you look to the upper right of the dot near the centre, almost exactly on the line*, you will see a small dot. This is at 73.8 on the y axis. If you want to use a different "Hubble constant", simply draw through the origin (0,0) to a point above or below my dot replacing my dot with your chosen value. N.B. For clarification, * 'My dot' is exactly on the line. The dot "almost exactly on the line" refers to the large dot close to the line. The line, if you remember, was drawn through the origin to the point I used in the line's construction.

Fill in any appropriate value based on your chosen Hubble constant, and you will see that the small variation in the line scarcely affects the situation at all, and certainly not the conclusions.

Cat

 

[Catastrophe]

Hmmm. Not my clearest description, let me try again.
To construct a line corresponding to alternative values of the Hubble constant, start from the origin and go along the x axis to 1.0 - and then go up the y axis to your chosen value, i.e., corresponding to my 73.8 - draw a line through the origin to your chosen point, and that is the corresponding Hubble's law line.

Cat

 

[Catastrophe]

Helio, what I did was to produce my rough graph - that was not rough in terms of accuracy. Just extra lines to help getting the points correct, writing names of galaxies against points, hoping some didn't overlap - things like that. This graph was on a graph paper pad. I then made the new graph by pushing a pin through the galaxy points. This ensured that they were correct and saved a lot of time. If you want the precursor graph put up here, to identify the galaxy points, I can do that. Also change Hubble constant line if you wish (on new graph).

The conclusion that the 'Hubble line' gives way to regional constraint was not unexpected. Obviously 'changeover' points of different galaxies will depend on gravity. There is some work to be done on correlating possibly 'deviant' points with galaxy mass, for example.

Anyway, I am at your bidding to further this important work.

Cat

 

[Helio]

You

OK. Here is the graph of speed km/sec vs distance megaparsecs.
I have added the "Hubble" line from zero (as they do) slope 73.8 (latest figure I found. Slight difference won't affect the picture too much.

Thanks to Helio for providing the data.

There are two interesting points, as I see it.
1) You have the "Hubble line) showing some galaxies following "Hubbles law" albeit very approximately.

These galaxies won't match the H-L constant because they are gravitationally bound to the barycenter of the Local Group. The data is only a snapshot of their motions toward or away from us. [Perhaps some Bayesian math can be used here to better work with probabilistic nature of the data.]

The question is whether these radial motions indicate they are influenced by the Hubble Flow (expansion) or not. If we assume the H-L constant must be applied to the radial results of the data, because expansion locally (Local Group) must apply, and we find that there is a tiny net outward movement. Then when we subtract this expansion effect and find that there is a net inward movement, does this suggest the expansion does affect our Local Group's orbital behavior? I think it does slightly favor that expansion better explains the data.

 

[Catastrophe]

To me, it looks like a hockey stick. The straight handle being the Hubble line, which bends over as the gravitational attractions 'pull the line away from straight, until only the distance is important.

I agree that it needs more data, if you want me to graph it. There is more I can do with this meanwhile.

Cat

 

[Helio]

To me, it looks like a hockey stick. The straight handle being the Hubble line, which bends over as the gravitational attractions 'pull the line away from straight, until only the distance is important.

I'm not understanding your view. Your graph shows that the galaxies are about evenly split above and below 0 kps, so that the HL line shows that the farthest galaxy is moving away slightly faster than the HL constant, so it seems to indicate the expansion helps explain that greater motion. Yet there are several other slightly less distant galaxies that have blueshifts.

What is interesting to me is the comparison of the net radial motion of all the galaxies, which I think favors the expansion explanation for what we see -- slight net expansion vs. contraction if we remove the HL constant.

 

[Phillip Huggan]

There is also Proxima C to consider. A small star orbiting where planets are projected to in a single or double big central star system. Remove the belching Alpha B and it is a two star system. Our neighbour isn't likely to hold big planets orbiting the star orbiting the central star. But another system may have an Oort cloud of planets with planets orbiting stars orbiting the central star. They aren't very stable planets. You need the multi-cellular life to happen quickly; no time for ice ball Earth, there.
I envision a pressurized cage with hollow tubes around a Brown Dwarf or white dwarf (3000AD). It might be improved in orbit around a quiet star that provides solar power.

 

[Catastrophe]

"I envision a pressurized cage with hollow tubes around a Brown Dwarf or white dwarf (3000AD)."

Sorry, are these natural, or some sort of artificial structure like:

Mystery of 'Alien Megastructure' Star Has Been Cracked (nationalgeographic.com


Cat

 

[Phillip Huggan]

Yes, that could be one square ring of the shopping cart cage. Cut an axis through it and add 6 more 30 degrees apart at 90 degrees perpendicular to the axis. Each tube is 1-10km in diameter. Life lives inside the tubes. The structure should be stable w/regard to the star/dwarf's gravity. The tubes rotate for G. It would clean out an Oort cloud. A wobbly spirograph orbit around the star/dwarf would give seasons as the distance to the star would change. After rotating around tether ships near Ice Moons, I'm not sure if this comes next or something else first. Maybe Webb can find a Nitrogen atmosphere near Earth's mass.

 

[Catastrophe]

It would clean out an Oort cloud.

This might take billions of years. Consider the diameter of a circle from the star, then multiply by π to get the circumference, then 'flesh out' the circumference to a torus, or maybe a spherical entity of great thickness. Then consider the contents of such an entity. Quite some undertaking!

Cat

 

[Phillip Huggan]

The manufacturing I envision won't work at 1.5g, probably. Big planets would be an issue. Below about 6nm, surface stress of particles "anneals" away most defects. It will be easy to make things out of nanowire than ball milling friction as the basic contruction step or weaving expensive carbon-allotropes. I guess you add ribbon rolling and folding payloads, and you get 1500x the weight in partially completed products. Many parts of rolling infrastructure won't be self-created. I'm assuming this is a little before fusion and a GUT to start...we should probably go for fusion and extremely delay a GUT, and either of those might make the station obsolete before it is ready. If we don't go for those two technologies, this would be a good use for a stable brown dwarf with toxic smaller planets. If it is too big, I'll look into really small including artificial heat sources and get the dimensions down to tens or hundreds of kms long at north-south axis.