Francis Pease – Dark matters

Francis Pease is known for his work on measuring star diameters, but here I will have a look at his work on spectroscopy of extragalactic objects. Francis Pease’s first extragalactic works were simply publishing measured radial velocities of galaxies and communicating some details on their spectra (Pease, 1915a, 1915b, 1915c, 1916a). Pease (1916b) was closing in on a redshift anomaly, although Pease didn’t seem to notice it then. He reported observations on NGC 4594 (a.k.a. Messier 104) and noted a strange feature:

Light was thus received from points at different distances from the nucleus. An extraordinary feature is that the relation between radial velocity and distance is sensibly linear, thus:
    Velocity = -2.78 x + 1180
in which x is the distance from the center in seconds of arc.

So, it seems that Pease might have published first account here of the flat rotation curves which currently are thought to suggest the presence of dark matter, but the level of detail is so poor in Pease’s paper that it is hard to say for sure. However, in the next paper, Pease (1916c) clearly recognizes that something is not correct there. This paper is basically the same observations reported with plenty more detail. Pease gives a table of his observations, and gives the same equation for the velocity curves. He notes that the equation was obtained from least squares fit, but he also says:

Within the limits of accuracy of the measures the change of rotational velocity is linear, although there may be some variation in individual parts of the nebula.

While interpreting this result, he says:

In any event the results seem to be inconsistent with a system involving planetary motion about a central nucleus, since this would require an increase of linear velocity toward the center of the nebula.

But Pease doesn’t give any comments about possible reasons for this. Pease (1918) studied the rotation curve of the Andromeda Galaxy, M31, and found it to have a linear rotation curve as well. But whether we should start to campaign for Pease as a founder of dark matter instead of Zwicky based on these studies presented here, I’m not so sure.


Pease, 1915a, PASP, 27, 133, “The Radial Velocity of the Nebula N. G. C. 1068”

Pease, 1915b, PASP, 27, 134, “Radial Velocity of the Andromedæ Nebula”

Pease, 1915c, PASP, 27, 239, “Radial Velocities of Six Nebulæ”

Pease, 1916a, PASP, 28, 33, “The Spiral Nebula Messier 33”

Pease, 1916b, PASP, 28, 191, “The Rotation and Radial Velocity of the Spiral Nebula N. G. C. C. 4594”

Pease, 1916c, PNAS, 2, 517, “The Rotation and Radial Velocity of the Spiral Nebula N. G. C. 4594”

Pease, 1918, PNAS, 4, 21, “The Rotation and Radial Velocity of the Central Part of the Andromeda nebula”


Wikipedia: Francis Pease

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