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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Galaxy Zoo | 4/5 | https://en.wikipedia.org/wiki/Galaxy_Zoo | reference | science, encyclopedia | 2026-05-05T03:49:12.688307+00:00 | kb-cron |
=== Related === In June 2019, citizen scientists through Galaxy Zoo reported that the usual Hubble classification, particularly concerning spiral galaxies, may not be supported, and may need updating.
== Rotation of galaxies ==
One of the original aims for Galaxy Zoo was to explore which way galaxies rotated. Cosmologist Kate Land stated: "Some people have argued that galaxies are rotating all in agreement with each other, not randomly as we'd expect. We want people to classify the galaxies according to which way they're rotating and I'll be able to go and see if there's anything bizarre going on. If there are any patterns that we're not expecting, it could really turn up some surprises." In Galaxy Zoo 1, volunteers were asked to judge from the SDSS images whether the galaxies were elliptical or spiral and, if spiral, whether they were rotating in a clockwise (Z-wise) or anti-clockwise (S-wise) direction. The rotation, also called the chirality, of galaxies has been examined in several Galaxy Zoo related papers. Among the results a psychological bias was demonstrated. Galaxy Zoo scientists wanted to determine whether spiral galaxies were evenly distributed, or whether an intrinsic property of the universe caused them to rotate one way or the other. When the Science team came to analyse the results, they found an excess of anticlockwise-spinning spiral galaxies. But when the team asked volunteers to classify the same images which had then been reversed, there was still an excess of anticlockwise classifications, delegating that the human brain has real difficulty discerning between something rotating clockwise or anticlockwise. Having measured this effect, the team could adjust for it, and established that spirals near each other tended to rotate in the same direction.
== Blue ellipticals and red spirals == Mainstream astronomical theory before Galaxy Zoo held that elliptical (or 'early type') galaxies were red in color and spiral (or 'late type') galaxies were blue in color: several papers published as a result of Galaxy Zoo have proved otherwise. A population of blue ellipticals was found. These are galaxies which have changed their shape from spiral to oval, but still have young stars in them. Indeed, Galaxy Zoo came about through Schawinski's searching for blue elliptical galaxies, as near the end of 2006, he had spent most of his waking hours trying to find these rare galaxies. Blueness in galaxies means that new stars are forming. However ellipticals are almost always red, indicating that they are full of old and dead stars. Thus, blue ellipticals are paradoxical, but give clues to star-formation in different types of galaxies. Also, a population of red spirals was found. These have a different evolutionary path from normal spiral galaxies, showing red spiral galaxies can stop making new stars without changing their shape. Using Galaxy Zoo data for their sample, Tojeiro et al. 2013 found (pg.5): 13,959 red ellipticals, 381 blue ellipticals, 5,139 blue late-type spirals, 294 red late-type spirals, 1,144 blue early-type spirals, and 1,265 red early-type spirals. Chris Lintott stated: "These red spiral galaxies had been lurking in the data and no-one had spotted them. They were staring us in the face. Now we know that a third of spirals around the edges of some clusters of galaxies are red." He also stated: "These results are possible thanks to a major scientific contribution from our many volunteer armchair astronomers. No group of professionals could have classified this many galaxies alone." A team using the Hubble Space Telescope has independently verified the existence of red spirals. Meghan Gray stated: "Our two projects have approached the problem from very different directions. It is gratifying to see that we each provide independent pieces of the puzzle pointing to the same conclusion." It is thought that Red Spirals are galaxies in the process of transition from young to old. They are more massive than blue spirals and are found on the outskirts of large clusters of galaxies. Chris Lintott stated: "We think what we're seeing is galaxies that have been gently strangled, so to speak, where somehow the gas supply for star formation has been cut off, but that they've been strangled so gently that the arms are still there." The cause might be the Red Spiral's gentle interaction with a galaxy cluster. He further explained: "The kind of thing we're imagining [is that] as the galaxy moves into a denser environment, there's lot of gas in clusters as well as galaxies, and it's possible the gas from the galaxy just gets stripped off by the denser medium it's plowing into."
== Dust in galaxies ==