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The main differences between elliptical and irregular galaxies is that elliptical galaxies have a discernable elongated disc like shape whereas irregular galaxies have no discernable shape, elliptical galaxies are up to 1 million light years in size whilst irregular galaxies are 20,000 light years and that elliptical galaxies are the older of the 2 galaxy types.
With that being said, there a still other differences so continue reading for a more detailed look at both galaxy types.
What Is An Elliptical Galaxy?
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Elliptical galaxies also named for their shape, being generally rounded and sometimes stretched more along one axis than another to give a cigar-type ellipse. The extent to which they are “squashed” is signified by classifying them from E0 (circular ball shape) to E7 (long, thin, cigar shape).
The largest galaxies in the known universe are elliptical although not all elliptical galaxies are formed on this scale.
They can range from giant elliptical galaxies containing a trillion stars and measuring millions of light-years across, to dwarf elliptical galaxies which may be less than 10% the size of the Milky Way or even so small that our telescopes may struggle to detect them.
While more spiral galaxies have been identified by astronomers, elliptical galaxies are actually thought to be more numerous, if less flashy and visible.
When specific sections of the sky are observed in depth, more elliptical galaxies tend to be found and if this pattern is repeated throughout the universe it would make them far more common.
What Is An Irregular Galaxy?
Irregular galaxies as their name would suggest, are galaxies distinguished by their unique shape and structure and make roughly 25% of all galaxies in the universe. In essence these galaxies don’t have a discernable shape like elliptical or spiral galaxies.
Although it isn’t quite clear how irregular galaxies were formed, there are a few hypothesis stating how they were made with the most common being that they were made as a result collisions between other galaxies.
Furthermore, these galaxies are considered middle of the pack regards to age as they’re believed to be older than spiral galaxies but younger than elliptical galaxies.
What this means is that irregular galaxies might have initially been separate, distinct spiral galaxies that ended up colliding with one another. Once this happened, the spiral shape was lost and their undiscernable shape emerged.
Being a galaxy also means they have a supermassive black hole at its center, and despite no concrete center point, it does seem to be case for the few irregular galaxies we’ve observed like NGC 6240 for example.
As for the what the different types of irregular galaxies are, the hubble classification established that irregular galaxies can fall one of type categories, either an Irr I or an Irr II.
Irr I have some semblance of a shape, but not enough to be able to be placed in either the elliptical or spiral categories. Irr II galaxies on the other hand have no are perceivable shape to them.
Are Elliptical Galaxies Smaller Than Irregular Galaxies?
No, elliptical galaxies are actually bigger than irregular galaxies.
This is because larger galaxies like spiral and of course elliptical are built to hold a discernable shape whilst irregular galaxies are not compact or designed to be in a normal regular shape but, a more scattered less obvious figure.
With that being said there is still nuance in regards to size as on average irregular galaxies are around 20,000 light years across. On the other hand elliptical galaxies can be anywhere from 10,000 light years to a million+ light years across.
It’s due to this upper range that elliptical galaxies are considered to be the largest galaxies in the world and certainly are not smaller than your typical irregular galaxy.
Similartities Between Elliptical And Irregular Galaxies
Both galaxies have supermassive black holes in their center, have millions to trillions of stars within its cluster, are made up of a variety of other dusts and clouds, they have a strong gravitational force that keeps everything together such as stars and among other components of the galaxy.
The core components of any given galaxy will be similar nevertheless, these two do function very differently from one another.
Differences Between Elliptical And Irregular Galaxies
As for what the differences between an elliptical and irregular galaxy are, they include the following:
- Elliptical galaxies have an elongated disc like oval shape whereas irregular galaxies come in a variety of unique undiscernable shapes and sizes as the name ‘irregular’ would suggest.
- Eliiptical galaxies are the largest galaxy type on avaerage where they can exceed 1 million light years in size whilst irregular galaxies tend to be around 20,000 light years across.
- Irregular galaxies don’t have a halo like structure surrounding them whilst elliptical galaxies do.
- Elliptical galaxies are the older of the two galaxies.
- Based on their size differences, although irregular galaxies aren’t necessarily dim, elliptical galaxy would be the brighter of the two.
- Irregular galaxies make up around 20 – 25% of all galaxies whereas elliptical galaxies make up less than 10%
Summary
Ultimatley what sperates the two is far less about how they function but more so based on how they look and the size differences between the two.
One has an easily distinguishable shape whilst the othe does not, ellipticals are both brighter and older than irregular galaxies and so on. In the end of it all both are galaxies and galaxies despite all the distinct differences between the two.
