Photographs STAR Moving 4800 MILES A SECOND (May, 1930)

This article is interesting for a number of reasons. One of the most interesting is that M.L Humasen was a high-school dropout who got a job as a janitor at Mt. Wilson Observatory where the was later made a member of the astronomical staff . He went on to take many of the observation that Edwin Hubble used to formulate Hubble’s Law. It’s odd that in the interview Humasen says he doesn’t believe the universe is “blowing up” which is precisely what Hubble’s Law says, though a bit less dramatically.

I’m a little confused about calling the object a star. N.G.C 4800 is actually a galaxy. Hubble was the one who proved, in the early 1920′s that these distant objects were outside the Milky Way and were in fact galaxies. Since they also refer to it as a nebula (which was sort of a catch-all term for blurry stellar objects at the time) I’m going to guess that it was just the reporter who decided it was a star.

I don’t know enough about solar spectra to be sure, but it seems like you wouldn’t be able to make a direct comparison of the spectra from a whole galaxy to that of one star. Incidentally N.G.C 4800 is actually 97.14 million light years away not the 50 million the article states.

Photographs STAR Moving 4800 MILES A SECOND

Sitting with his eye glued to a telescopic camera for 45 hours, M. L. Humason, Mt. Wilson astronomer, has succeeded in setting a record for long distance photographs. The nebula on which he trained his camera is 50,000,000 light years away from the earth.

FOR 45 hours in total darkness, Milton L. Humason, member of the astronomical staff at the Mt. Wilson observatory at Pasadena, California, trained the world’s largest telescope toward a far distant point in the heavens and obtained a photograph of a nebula 50,000,000 light years away from the earth—a total of 300 quintillion miles.

While the actual picture of the nebula shows it to be only a pin point among other and less distant stars, what Mr. Humason actually pictured was one of the brightest nebulae in the heavens.

Due to the distance, the amount of light which reached his photographic plate from this nebula is so faint that ordinary telescopes cannot photograph its spectrum. Even the 100-inch telescope had to be held on it all night every night for a week before the inflowing waves of light could be gathered together in the world’s largest reflector and funnelled into an image strong enough to record the spectrum on a photographic plate.

While the nebula has no name, it is known as N. G. C. 4860, which merely means that it is number 4860 in the Mt. Wilson new general catalogue.

Mr. Humason worked in total darkness, because light from any other source than the object would have spoiled the picture. He pointed the telescope toward the object and a driving clock held it in the proper position despite the earth’s rotation. Without the driving clock the telescope would have moved with Mt. Wilson out of alignment.

While the driving clock is as accurate as clock works can be made, Mr. Humason kept his eyes constantly on the slit through which the focused light passes to the prisms and the camera, and corrected any wanderings of the image.

“The light entered the barrel of the telescope striking the 100-inch reflector at the lower end and was reflected back to a smaller mirror at the top,” Mr. Humason explains.

“This reflected the light down the tube again, bringing it to a focus at a slit under the eyes of the observer. Passing through the slit the focused light would strike a series of prisms which broke it into colors, and that is the spectrum I photographed. Falling for a long time on a sensitive photographic plate, even this very faint light finally made an impression.”

The spectrum of the nebulae, when compared with the spectrum of the sun, revealed that the object is moving away from the earth at a speed of 4800 miles a second.

“Interpreting this in the established way,” says Mr. Humason, “it would look as if the whole universe were exploding, scattering into space, entire nebulae flying away faster than shells from a cannon, but I don’t believe the universe is blowing up.”

While photographing this rapidly receding nebulae, Mr. Humason had to control the focus and the comparison spectrum, keep the temperature of the spectrograph exactly right throughout the night. Sitting in total darkness with his eyes on a slit of dim light little larger than a pin head, he worked levers and pushed buttons for seven nights without moving the photographic plate or losing sight of the faintly luminous spot in the sky. Here Mr. Humason brought romance of the heavens down to earth.

Mr. Humason and his fellow astronomers have been unable to determine whether the huge velocity—4800 miles a second —is real, or whether the indication comes from a slowing down of the light waves due to distortion in space, or to forces acting on the waves during their long journey to earth.

By the taking of this long distance photograph and other experiments at Mt. Wilson, the astronomers are attempting to test Einstein’s contention that the entire universe of space and time are curved. They are attempting to test it not mathematically, but by actual observation.

Mr. Humason’s long distance photograph goes to the very heart of the problem. The light by which the photograph was taken comes from the remotest region of the universe. It is not local light, not light radiated from within our own galaxy. It originates far outside.

4 comments
  1. GaryM says: January 26, 201210:30 am

    The caption writer seems uncertain whether that’s one nebula or multiple nebulae.

  2. Jari says: January 26, 201211:08 am

    Charlie: Galaxies are mostly composed of hydrogen, just like a main sequence star. In this case hydrogen’s spectral lines are redshifted compared to the sun and you can calculate the radial velocity of the galaxy.

  3. Charlie says: January 27, 20128:00 am

    Jari: I think they are similar, but different stars give off different spectra and without a pretty modern telescope I think all you’d see is the combined spectra of all of the light emitted from the galaxy. http://outreach.atnf.cs…

    I think you could probably just pick out the hydrogen lines and just use those, but I’m not entirely sure.

  4. Jari says: January 27, 201211:19 am

    Charlie: Yes, the light from a galaxy is a sum of all it’s stars and other glowing things. And then you can pick eg. H-alpha line from the spectra, like in that article you linked. H-alpha line in the Sun’s spectra slightly under 660 nm, while in those examples, that you linked, it have redshifted to the longer wavelengths : http://www.regulusastro…

Submit comment

You must be logged in to post a comment.