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In 1923, following the Great Debate, it became clear that many "nebulae" were in fact galaxies far from the Milky Way. Slipher and Edwin Hubble continued to collect the spectra from many different nebulae, finding 29 that showed emission spectra and 33 that had the continuous spectra of star light. [18]
Box Nebula NGC 6445: 1786 4.5 11.2 Sagittarius: Eye of Sauron Nebula M 1-42: 10 14 Sagittarius
About 3000 planetary nebulae are now known to exist in our galaxy, [47] out of 200 billion stars. Their very short lifetime compared to total stellar lifetime accounts for their rarity. They are found mostly near the plane of the Milky Way, with the greatest concentration near the Galactic Center. [48]
The following well-known nebulae are listed for the purpose of comparison. Orion Nebula: 20 ly (6.132 pc) [64] Diffuse Nebula: The closest major star formation region to Earth. [65] Crab Nebula: 11 ly (3.4 pc) [66] Supernova remnant: The remnant of a supernova that occurred in 1054 AD. [67] Bubble Nebula: 6 [68]-10 [69] [70] ly (1.84-3.066 pc ...
This video clip shows a visualization of the three-dimensional structure of the Pillars of Creation. Closer view of one pillar. Pillars of Creation is a photograph taken by the Hubble Space Telescope of elephant trunks of interstellar gas and dust in the Eagle Nebula, in the Serpens constellation, some 6,500–7,000 light-years (2,000–2,100 pc; 61–66 Em) from Earth. [1]
1750 – Thomas Wright discusses galaxies and the flattened shape of the Milky Way and speculates nebulae as separate. [11] 1755 – Immanuel Kant drawing on Wright's work conjectures that our galaxy is a rotating disk of stars held together by gravity, and that the nebulae are separate such galaxies; he calls them Island Universes.
The evolving star may eject some portion of its atmosphere to form a nebula, either steadily to form a planetary nebula or in a supernova explosion that leaves a remnant. Depending on the initial mass of the star and the presence or absence of a companion, a star may spend the last part of its life as a compact object ; either a white dwarf ...
Galaxies, averaging an estimated 100 million stars, [3] range in size from dwarfs with less than a thousand stars, [4] to the largest galaxies known – supergiants with one hundred trillion stars, each orbiting its galaxy's center of mass. Most of the mass in a typical galaxy is in the form of dark matter, with only a few percent of that mass ...