Spiral galaxies with a jumper - spiral galaxies with a jumper ("bar") of bright stars emerging from the center and crossing the galaxy in the middle. The spiral branches in such galaxies begin at the ends of the jumpers, while in ordinary spiral galaxies they exit directly from the nucleus.
In his classification, Edwin Hubble typed such galaxies as “SB” and divided them into three subcategories, depending on how tightly twisted the spiral branches are. Type SBa is characterized by the most densely twisted branches, while in type SBc they are practically not twisted. The intermediate type of bridged spiral galaxies is denoted as SBb. Later, to describe some irregular spirals with a jumper, a fourth subcategory, SBm , was introduced. This subcategory includes the Magellanic Clouds , which were previously considered irregular galaxies , but subsequently discovered the structural features of spiral galaxies with a jumper.
In 2005, when working with the Spitzer space telescope and based on earlier observations, it was found that the Milky Way should also be attributed to spiral galaxies with a jumper. The hypothesis of a jumper in our galaxy was put forward on the basis of numerous data from radio telescopes. However, only thanks to images from Spitzer operating in the infrared range, this assumption was firmly confirmed.
Content
Jumpers
Spiral galaxies with a jumper are quite numerous. Observations show that approximately two-thirds of spiral galaxies have a jumper [1] . According to existing hypotheses, jumpers are centers of star formation , supporting the birth of stars in their centers. It is assumed that through orbital resonance , they pass gas from spiral branches through themselves. This mechanism provides the influx of building material for the birth of new stars [2] . Based on this hypothesis, one can also explain why many spiral galaxies with a jumper have active nuclei .
The appearance of the jumper is associated with compaction waves emanating from the center of the galaxy and changing the orbits of the nearest stars. This process creates the conditions for further perturbation of stellar motions, due to which self-supporting jumpers arise [3] . Another possible reason for the appearance of jumpers is the tidal interactions of galaxies.
Jumpers are probably a temporary phenomenon in the life of spiral galaxies. Gradually, the jumper collapses, and the galaxy turns from a spiral with a jumper into a regular spiral. The longevity of the jumper is determined by its mass. Spiral galaxies with a jumper, which have collected a large amount of matter in their center, have short highly stable jumpers. Based on the fact that many spiral galaxies have a jumper, it can be concluded that this stage is important in the evolution of a spiral galaxy.
Bulge
In the process of studying the core of the Milky Way, scientists discovered that the bulge of our galaxy has an elongated shape. This led to the idea that all galaxies with jumpers have an elongated bulge. When observing distant spiral galaxies, the axis of rotation of which is perpendicular to the axis of view, that is, when the galaxy is turned to us by an edge, the elongation of the bulge can be easily detected. This makes it possible to easily attribute a similar galaxy to either a conventional spiral or a spiral with a jumper.
Examples
| Title | Type of | Constellation |
|---|---|---|
| M58 | Sbc | Virgo |
| M91 | SBb | Veronica's hair |
| M109 | SBb | Big Dipper |
Sources
- ↑ PB Eskridge, JA Frogel. What is the True Fraction of Barred Spiral Galaxies? (Eng.) // Astrophysics and Space Science : journal. - 1999. - Vol. 269/270 . - P. 427-430 .
- ↑ JH Knapen, D. Pérez-Ramírez, S. Laine. Circumnuclear regions in barred spiral galaxies - II. Relations to host galaxies (Eng.) // Monthly Notice of the Royal Astronomical Society: journal. - 2002. - Vol. 337 , no. 3 . - P. 808-828 .
- ↑ F. Bournaud, F. Combes. Gas accretion on spiral galaxies: Bar formation and renewal ( Astronomy and Astrophysics : journal. - 2002. - Vol. 392 . - P. 83-102 .