Edward Fath – early spectroscopy of galaxies

Although I’m concentrating on Fath’s extragalactic work, I’ll mention a paper among his early works as a curiosity; Steppins & Fath (1906), titled “The Use of Astronomical Telescopes in Determining the Speeds of Migrating Birds”.

Fath (1909) measured spectra of spiral galaxies, but he wasn’t able to determine their redshifts. He noted that by that time, general concensus was that spiral galaxies have continuous spectrum and that there were only two studies casting doubt on that. Both of them were inconclusive according to Fath. Fath then discussed the spectra of individual objects. He noted on the Andromeda galaxy (M31):

It contains little more than the spectrum of nucleus, which is not of a stellar character.

Some other objects he measured were NGC 1068 (of which there seemed to be a debate ongoing if it even is a spiral galaxy, or “spiral nebula” as they were called back then), NGC 3031 and NGC 4736. On NGC 5194, he said:

Photographically it is faint. Because of this it is not a promising object for spectrographic analysis, but it seemed best to make an attempt. … The plate showed nothing.

Well, you can’t succeed every time… He summed up his research on the question of the spectrum of spiral galaxies:

No spiral nebula investigated has a truly continuous spectrum.

Fath then proceeded to interesting discussion on the possible explanation for the spectrum of spiral galaxies. He notes that the spectrum usually comes only from the nuclei of spiral galaxies and resembles stellar spectrum, then he says:

The hypothesis that the central portion of a nebula like the famous one in Andromeda is a single star may be rejected at once unless we wish to modify greatly the commonly accepted ideas as to what constitutes a star.

He says that a possible explanation would be a star cluster at the center but asks:

Is it reasonable to assume that in a condensed cluster we should have stars of one spectral type strongly predominating?

He mentioned that there weren’t enough spectral measurements of star clusters to determine the answer to this question, so he proceeded to measure a few star clusters himself. He found out that one spectral type can predominate strongly. He then considered a parallax measurement of Andromeda galaxy and noted that the value of the parallax leads to the impossibly small sizes of hypothesized star cluster members. So, Fath is left with a hypothesis that to his knowledge is only one that can explain the spectrum, but other evidence rather conclusively show that the hypothesis is not likely to be valid.

Fath (1910) discussed some aspects of the distribution of spiral galaxies in the sky. Fath (1911) continued with spiral galaxy spectra. He gave some new spectral information on individual objects, and then suggested a preliminary spectral type division for all nebulae. Fath (1913) was his third paper on the subject, and here he only discussed individual objects.

Although Fath showed that the spectrum of spiral galaxies is not continuous but that it contains spectral lines, he didn’t discuss the possibility of measuring the redshifts of galaxies.

Links

Not much information is available on Edward Fath, but here’s at least something:

A Science Not Earthbound: A Brief History of Astronomy at Carleton College, page 11

References

Fath, 1909, LicOB, 5, 71, “The spectra of some spiral nebulae and globular star clusters”

Fath, 1910, PA, 18, 544, “The Distribution of Nebulae and Globular Star Clusters”

Fath, 1911, ApJ, 33, 58, “The spectra of spiral nebulae and globular star clusters”

Fath, 1913, ApJ, 37, 198, “The spectra of spiral nebulae and globular star clusters”

Stebbins & Fath, 1906, Sci, 24, 49, “The Use of Astronomical Telescopes in Determining the Speeds of Migrating Birds”

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: