Spiral nebula

Spiral Nebula
Related Category: Astronomy: General
see galaxy.
More on Spiral Nebula
Galaxy - large aggregation of stars, gas, and dust, typically containing billions of stars.

SPIRAL NEBULAE AND GLOBULAR CLUSTERS
We have just seen how astronomers' attempts to probe the Galactic disk by optical means are frustrated by the effects of the interstellar medium, whereas looking in other directions, out of the Milky Way plane, ...

spiral nebula: Nebulous object with a spiral appearance observed in early telescopes; later recognized as a spiral galaxy.

Spiral Nebula
A spiral galaxy - not really a nebula at all (although many do appear nebulous).
Spiritualism ...

Question Mark Spiral Nebula
It was soon followed by M99
North America Nebula Wikipedia
Pelican Nebula Wikipedia ...

1922 - Vesto Slipher summarizes his findings on the spiral nebulae's systematic redshifts
1922 - Alexander Friedmann finds a solution to the Einstein field equations which suggests a general expansion of space ...

In 1912 Vesto Slipher measured the first Doppler shift of a "spiral nebula" (spiral nebula is the obsolete term for spiral galaxies), and soon discovered that almost all such nebulae were receding from Earth.

In the 1910s, Vesto Slipher and later Carl Wilhelm Wirtz interpreted the red shift of spiral nebulae as a Doppler shift that indicated they were receding from Earth.

Spiral nebulae have the remarkable characteristic of avoiding the galactic plane, and it has been suggested that the space outside the limits of the stellar universe is filled with them.

In 1914 Vesto Slipher (lived 1870--1963) announced his results from the spectra of over 40 spiral galaxies (at his time people thought the ``spiral nebulae'' were inside the Milky Way).

The other fellow, Heber Curtis (1872-1942), studied the spiral nebulae quite a bit, so he was really the expert when it came to those things.

Shapley believed that the Milky Way was vastly greater in size than previous estimates, and that spiral nebulae were a part of it. On the other hand, Curtis believed that spiral nebulae were in fact island Universes, that lay beyond the Milky Way.

The zone of avoidance gave rise to an important question in the early part of the twentieth century, when astronomers were trying to figure out exactly what spiral nebulae were.

Curtis, held a great debate about the nature of these "spiral nebulae". Were they objects within the Milky Way, or were they communities of stars distinct from our Galaxy?

This settled the question as to whether or not the spiral nebula were galaxies. Hubble was able to observe Cepheids in other galaxies as well and so obtain distances to them.

He became a proponent of the "island universes" hypothesis, which held that the spiral nebulae were actually independent galaxies.

We thought they were in our galaxy and were called spiral nebulae. Today, we mainly use two methods to measure the distances to other galaxies. The first one is the Cepheid variables that we have talked about in Chapter 13.

In the 1920s and 1930s, Edwin Hubble had become famous for discovering that the spiral nebulae were in fact galaxies beyond ours, and that the Universe was expanding.

He thus established conclusively that these "spiral nebulae" were in fact other galaxies and not part of our Milky Way. This was a momentous discovery and dramatically expanded the scale of he known Universe.

In 1923, Edwin Hubble showed that the "spiral nebulae" that were presumed to be within our galaxy, the Milky Way, were actually other galaxies that lay far beyond our.

Photography turned up myriads of such spiral nebulae, particularly with work around 1900 by Keeler and Curtis with the 36" Crossley reflector at Lick Observatory.

Studies conducted by the American astronomer Edwin Hubble resolved in 1924 the question as to the nature of the spiral nebulae, showing them to be individual galaxies like the Milky Way but located at very great distances.

Hypothesis, maintained in the nineteenth and early twentieth century, that the spiral nebulae are not galaxies but are instead whirlpools of gas from which new systems of stars and planets are condensing. Compare Island Universe Theory [F88] ...

Until the early twentieth century, astronomers thought the Milky Way was the sole constituent of the universe. Then they discovered that the spiral nebulae -- fuzzy objects found all over the night sky -- are large systems of stars.

See also: Nebula, Galaxies, Galaxy, Universe, Distance