Nebulae

The central star of the Ring Nebula, also known as Messier 57, is a white dwarf. A white dwarf is a dense, compact stellar remnant that is left behind after a star like our Sun exhausts its nuclear fuel and sheds its outer layers.

The Horsehead Nebula was discovered by Mrs. Williamina Fleming on Harvard College Observatory Bache Telescope plate B2312, noted by Professor E. C. Pickering in his Harvard Annals publication of new objects discovered by photography at Harvard in Cambridge, Massachusetts, published in 1890. The discovery was made by her on June 27, 1888, and the plate was exposed on February 6, 1888. It was Mrs. Fleming's job to examine and analyze the photographs for details and possible new objects. Professor Pickering also reported that his brother, William, had immediately speculated that the nebula consisted of dark, obscuring matter: and thus from the very beginning, the correct scientific nature of the phenomenon was comprehended.

However, though the large bright nebula IC-434, upon which the Horsehead is superimposed on Earth's line of sight, was catalogued in 1895 (with a mistaken attribution to "Pickering", not Fleming), the Horsehead itself was not generally acknowledged in astronomical catalogues for some years, until Edward E. Barnard included it as his item no. 33 in a paper containing a list of 182 dark 'markings', published in 1919. Though others photographed the Horsehead after 1891, Barnard was apparently the first person to observe and study it visually, in 1913.

Stephen Waldee, a California amateur astronomer and researcher, turned up the forgotten and unacknowledged facts in the old Harvard publication and -- with the cooperation of Martha Hazen, Curator of Harvard's Historical Photographs -- the original plate, during a research project in 1989/90. The saga of Mrs. Fleming's work on the nebula and other such objects discovered in Harvard's early photographic program was chronicled and published over the next few years, in a joint Waldee-Hazen paper, a magazine article, and eventually a large research website. Mrs. Fleming's work was finally professionally recognized (unfortunately not her Horsehead discovery!) in 1908, with the publication of the second Index Catalogue; she found no fewer than 59 gaseous nebulae on various Harvard photographs made in Massachusetts and Arequipa, Peru. In addition she discovered novae and hundreds of variable stars. But her seminal discovery of the Horsehead was not understood prior to the Waldee-Hazen paper of 1990. -- Stephen R. Waldee

Gravitational force pulled the particles of gas and dust together, causing the solar nebula to shrink and eventually form the solar system.

Planetary nebulae are formed from the ejected outer layers of certain types of stars, such as red giants, during the late stages of their evolution. Despite their name, they have nothing to do with planets. They often have complex and beautiful shapes due to interactions with the surrounding interstellar medium.

Some examples of different nebulae include the Orion Nebula, the Crab Nebula, the Eagle Nebula, and the Helix Nebula. These nebulae vary in size, shape, and composition, but they are all vast clouds of dust, gas, and plasma in space.

Becuase nebulae tell us how stars get formed so the composition, density and size of a nebulae cloud says a lot about its age, likelihood of stars forming and the type of stars that might form.

No, the solar nebula was primarily composed of hydrogen and helium, with trace amounts of other elements like carbon and iron. The solar system formed from the gravitational collapse of this nebula, leading to the formation of the Sun and planets.

I had taken a course on the universe at UCR and my professor, a graduate of MIT, said that it took approximately 30 days for the moon to form after a planetoid collided with Earth. Yes, days haha

The Greek root "nebula" means cloud or mist. It is often used in scientific terms related to astronomy, referring to a cloud in outer space consisting of gas or dust.