by: Rose Zimmerman

Main Points  Shape  Classification  Properties  Large Magellanic Cloud  Small Magellanic Cloud  Dwarf Irregular Galaxy  Stars of an Irregular Galaxy  Where Irregular Galaxies are found  The Hubble Sequence  Hertzsprung-Russell Diagram  Percentage

Shape  Irregular galaxies are often chaotic in shape, with no central bulge or spiral arms.  Although they used to have a more familiar shape, a dramatic collision with another galaxy has distorted their shape.

How are irregular galaxies formed?  Irregular galaxies don't start out being irregular, most start out as regular galaxies such as spirals or ellipticals that are then twisted into different shapes by the gravitational influence of collisions. Dwarf Irregular Galaxy Irregular Galaxy

Classifications There are two types of classifications that scientists use to classify irregular galaxies…  Irr-I Galaxy which have some structure but are distorted enough to not be elliptical or spiral.  Irr-II Galaxy doesn’t have any structure. Irr-I Galaxy Irr-II Galaxy

Properties of Irregular Galaxies  Solar masses that range from 10 8 to (1/1000 mass of spiral or elliptical galaxies)  Diameters from 1 to 10 kpc  Blue magnitudes from -13 to -20  Don’t have many systematic features

Stars of an Irregular Galaxy Irregular galaxies are usually made up of young stars which are blue. They also are very hot stars and lots of gas and dust. Blue Stars that make up an Irregular Galaxy.

Where are Irregular Galaxies found? Irregular galaxies are usually found in groups or clusters, where collisions and near-misses between galaxies are common. In a few irregular galaxies, astronomers can't figure out why they look so strange. Galaxy collision cause of irregular galaxy

Magnetic Field  Magnetic fields are an important component of the interstellar medium, especially in low-mass galaxies like irregulars where the magnetic pressure may be significant. However, few irregular galaxies have observed magnetic field structures.

Percentage  Only 3% of galaxies are irregular.

Large Magellanic Cloud If you live near the equator you are able to see the Large Magellanic Cloud (LMC) is an irregular-shaped galaxy seen in the southern irregular shape could have been caused by the collision of two other galaxies. Large Magellanic Cloud located near the constellation Dorado and 163,00 light years away.

Small Magellanic Cloud The Small Magellanic Cloud is a dwarf irregular galaxy that is about 200,000 light years from the milky way making it look as if it is a detached part of our galaxy. Astronomers think that the Small Magellanic Cloud was once a spiral galaxy but changed because of the gravity in the Milky Way. Small Magellanic Cloud in the constellation of Tucana

Dwarf Irregular Galaxy Sagittarius Dwarf Irregular Galaxy  Small  Unstructured  Irregular shape  Gas-rich  Metal poor  Have varying levels of star formation

The Hubble Sequence  The Hubble sequence is a morphological classification scheme for galaxies invented by Edwin Hubble in Hubble’s scheme divides regular galaxies into 3 broad classes – ellipticals, lenticulars and spirals - based on their visual appearance (originally on photographic plates). A fourth class contains galaxies with an irregular appearance. To this day, the Hubble sequence is the most commonly used system for classifying galaxies, both in professional astronomical research and in amateur astronomy.  ype The Hubble Sequence used to identify the type of galaxy

Hertzsprung-Russell diagram  The graph showing the absolute magnitude plotted against the surface temperature for a group of stars. The Hertzsprung-Russell Diagram can be used to find out what types of stars make up an irregular galaxy.

Pictures….

Work Cited        