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Red Shift Distances Using Hubble Constant
Hubble's Constant usage seems to vary among objects in Wikipedia with both an accepted distance and velocity. The H value is easily calculated with V / D. A small random sample reveals different H values are being used. A different H selection means this object's calculated distance is not consistent with others.
Astronomers claim Hubble's Law can translate a red shift into a distance but it appears astronomers use varying values of Hubble's Constant for different objects.
This constant converts a velocity (in km/s) into distance (Mpc), where Distance = Velocity / H
From Wikipedia:
'
The Hubble constant is about 70 (km/s)/Mpc.
More recent measurements from the Planck mission published in 2018 indicate a lower value of 67.66±0.42% although, even more recently, in March 2019, a higher value of 74.03±1.42% has been determined using an improved procedure involving the Hubble Space Telescope. The two measurements disagree at the 4.4-sigma level, beyond a plausible level of chance.
'
Astronomers must select an H value when a red shift value is obtained. Its value has been changing. There are no defined criteria for this selection of H.
Here are several objects with their red shift velocity and the accepted distance (data from Wikipedia), with the corresponding H value that was used for that 'published' combination.
Sometimes Wikipedia has both Mly and Mpc or just one.
In the following:
Z = red shift; V = km/s, D= Mpc
accepted values of Z and D for M104
The exercise is:
1) calculate the H from the values provided
2) calculate the D with H = 72 (midpoint of 70 and 74)
3) calculate the D with the integer value of the calculated H
This provides 3 values of D to compare.
M104 Z = 0.003416 V = 1024 at D = 9.55 so from V/D H= 107.23
D calculated from Z:
M104 Z = 0.003416 so V = 1024.8 with H = 72 then D = 14.23
M104 Z = 0.003416 so V = 1024.8 with H=107 then D = 9.58
M104 used a higher H than 'normal' 70 or the 'latest' 74.
accepted values of Z and D for M60
M60 Z = 0.003726 V = 1108 at D = 17.8 so from V/D H= 62.25
D calculated from Z:
M60 Z = 0.003726 so V = 1117.8 with H = 72 then D = 15.53
M60 Z = 0.003726 V = 1117.8 with H = 62 then D = 18.0
M60 used H lower than 'normal' 70 or the 'latest' 74.
accepted values of V and D for Hoag's Object
Hoag's Object V = 12740 at D = 187.9 so from V/D H= 67.8
D calculated from V:
Hoag's Object V = 12740 with H=70 then D = 182.0
Hoag's Object used H near 'normal' 70 or the 'latest' 74.
accepted values of Z and D for Abell 133
Abell 133 Z = 0.00566 V = 16968 at D = 234 so from V/D H= 72.51
D calculated from Z:
Abell 133 Z = 0.00566 V = 16968 with H = 72 then D = 235.83
Abell 133 used H higher than 'normal' 70 but lower than the 'latest' 74.
accepted values, Z & D for 3C 273
3C 273 Z = 0.158339 so V = 47501.7 at D = 749 so from V/D H= 63.42
D calculated from Z:
3C 273 Z = 0.158339 so V = 47501.7 with H = 70 then D = 678.6
3C 273 Z = 0.158339 so V = 47501.7 with H = 63 then D = 754
3C 273 used H lower than 'normal' 70 or the 'latest' 74.
accepted values, Z & D for NGC 67
NGC 67 Z = 0.020734 so V = 6220 at D = 84.3 so from V/D H= 73.77
D calculated from Z:
NGC 67 Z = 0.020734 so V = 6220 with H = 70 then D = 88.9
NGC 67 Z = 0.020734 so V = 6220 with H = 73 then D = 85.2
NGC 67 used H lower than 'normal' 70 but almost the 'latest' 74.
A sample of 6 found none to use 70, the accepted value according to Wikipedia. Even if Wikipedia has the wrong value for H these 6 in the sample do not use the same H value.
There are concerted efforts to take measurements to find the most accurate value of H.
This small sample indicates that accepted H value or its latest H value are rarely used.
I did not continue checking further objects. A sample of 6 might be small but all used different values.
Using different values of H obviously affects the distance.
After this simple exercise I have little confidence in distances provided, sometimes with a decimal point indicating precision.
A much larger sample is required to see if any pattern of the H selection can be discerned. I did not bother.
Anyone can do the simple V/D to see the H being used.
I expected to find one H value was being used consistently.
That is not the case.
Perhaps this is trivial but I expect consistency with critical values.
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