![]() It is spherically shaped, and only contains old stars. ![]() The bulge is housed at the center of the galaxy. These types of galaxies are classified by their 3 main components – a disk, bulge, and halo. Of all the known galaxies in the universe, 77% of them are classified as spiral galaxies. Named for their shape, spiral galaxies are the most common type of galaxy in the universe. The following image of the Whirlpool Galaxy is one of my favorites. To accomplish these detailed galaxy portraits, I take long-exposure images using a monochrome camera on an equatorial telescope mount. Over the years I have photographed several galaxies from my backyard using my camera and telescope. If you want to see some of the most incredible galaxy photos ever taken, be sure to visit the Hubble Space Telescope Image Archives: Galaxies. This shape classification of galaxies was created by Edwin Hubble in 1926 which he laid out in a diagram called the Hubble Tuning Fork, because of the diagram’s resemblance in shape to a tuning fork. The other general classifications of galaxies include spiral galaxies, elliptical galaxies, and irregular galaxies. Within galaxies, there are also planets, black holes, moons, comets, and dark matter.įor example, the Milky Way, the solar system in which we reside, is classified as a barred spiral galaxy because of its general spiral shape accompanied by a bar and disk of stars at the center. Although these are the four main types, there are various types of galaxies and the way in which they are classified is by their shape.Ī galaxy is a cluster of stars, gas, and dust that are kept together by the force of gravity. A 2008 investigation found that only 20 percent of the spiral galaxies in the distant past possessed bars, compared with about 65 percent of their local counterparts.There are four distinct types of galaxies in the universe, elliptical, spiral, barred spiral, and irregular. Recent studies have confirmed the idea that bars are a sign of galaxies reaching full maturity as the "formative years" end. The oscillating evolutionary cycle from spiral galaxy to barred spiral galaxy is thought to take on the average about two billion years. Since so many spiral galaxies have bar structures, it is likely that they are recurring phenomena in spiral galaxy development. Barred spiral galaxies with high mass accumulated in their center tend to have short, stubby bars. Past a certain size the accumulated mass of the bar compromises the stability of the overall bar structure. This effect builds over time to stars orbiting further out, which creates a self-perpetuating bar structure.īars are thought to be temporary phenomena in the lives of spiral galaxies the bar structures decay over time, transforming galaxies from barred spirals to more "regular" spiral patterns. The creation of the bar is generally thought to be the result of a density wave radiating from the center of the galaxy whose effects reshape the orbits of the inner stars. This process is also thought to explain why many barred spiral galaxies have active galactic nuclei, such as that seen in the Southern Pinwheel Galaxy. The bar is thought to act as a mechanism that channels gas inwards from the spiral arms through orbital resonance, in effect funneling the flow to create new stars. The current hypothesis is that the bar structure acts as a type of stellar nursery, fueling star birth at their centers. Among other types in Hubble's classifications for the galaxies are the spiral galaxy, elliptical galaxy and irregular galaxy.īarred galaxies are apparently predominant, with surveys showing that up to two-thirds of all spiral galaxies contain a bar. A new type, SBm, was subsequently created to describe somewhat irregular barred spirals, such as the Magellanic Cloud galaxies, which were once classified as irregular galaxies, but have since been found to contain barred spiral structures. SBb-type galaxies lie in between the two. SBa types feature tightly bound arms, while SBc types are at the other extreme and have loosely bound arms. The Milky Way Galaxy is classified as a barred spiral galaxy.Įdwin Hubble classified spiral galaxies of this type as "SB" (spiral, barred) in his Hubble sequence and arranged them into sub-categories based on how open the arms of the spiral are. Bars generally affect both the motions of stars and interstellar gas within spiral galaxies and can affect spiral arms as well. Bars are found in approximately two-thirds of all spiral galaxies. A barred spiral galaxy is a type of spiral galaxy with a central bar-shaped structure composed of stars.
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