Barred spiral galaxy

A barred spiral galaxy, or shortly called barred galaxy, is a spiral galaxy with a more or less straight band of bright stars. This " bar" extends from the center of the galaxy up into different distances, in some cases almost to the edge. The spiral arms are based on the ends of the beam.

Edwin Hubble classified these types of spiral galaxies as " SB" (English " Barred Spiral " ), and divided them according to the expression of the bar and the spiral arms into three subcategories:

• SBa galaxies have a large bar-shaped core, the spiral arms are almost closed ring.
• SBb galaxies have strongly emphasized arms and a weaker core
• SBc galaxies have S -shaped arms that are only slightly curved. Instead of a core, they only have a central bulge.

It was later added a fourth category:

• SBm galaxies are dwarf barred spiral galaxies. The large Magellanic Cloud is one according to recent findings probably to this group.

Barred spiral galaxies are relatively frequent. Studies show that up to 2 /3 of all spiral galaxies have a bar structure. The Milky Way is a barred spiral galaxy also.

The area of ​​the bar represents an active star formation region dar. This gas flows from the form to the stars of the spiral arms towards the center of the galaxy.

The beam structure is the result of a density wave that propagates radially from the center of the galaxy and affects the orbits of the inner star. It is possible that the structure forms but also a result of mutual gravitational disturbances of galaxies.

It is believed that barred spirals represent only a temporary stage in the evolution of galaxies. The barred spirals form from the passage of time to " normal " spiral galaxies.

Videos

• How are bar - galaxies? from the TV - series alpha Centauri (about 15 minutes). First aired on Dec. 7. 2005.

• Galaxy