Objective classification of spiral galaxies

In summary, the conversation discusses the subjectivity of the Hubble classification of galaxies and the search for a more objective method of observing and comparing the morphological types of galaxies. The En number formula is provided as an objective method for elliptical galaxies, but the conversation acknowledges the lack of a similar method for spiral galaxies. Suggestions are made to look at color-mass diagrams for a more objective classification scheme.
  • #1
henrco
47
2
I have question that has been troubling me and I was hoping someone may be able to help me.

I've always thought the Hubble classification of galaxies was a bit subjective. I was recently looking at some images online of galaxies and I was wondering how you might objectively observe and compare the morphological types of galaxies, from CCD images.With Elliptical galaxies you can derive the En number where the number n describes the apparent axial ratio (b/a) by the formula: n=10 [1 – (b/a)], (1) where a and b represent the length of the semi‐major and semi‐minor axis, respectively, of the galaxy. So that's pretty objective.However how do you objectively do the same for Spiral galaxies? After numerous searches I haven't found a method that is similar to the one for elliptical galaxies above.
 
Astronomy news on Phys.org
  • #2
The Hubble classification is quite subjective. If you want a more objective classification scheme, try looking at these color-mass diagrams, which effectively separate galaxies into ellipticals and spirals.
 

1. What is the purpose of objective classification of spiral galaxies?

The purpose of objective classification of spiral galaxies is to provide a standardized and systematic way of categorizing these galaxies based on their physical properties. This allows scientists to better understand the diversity and evolution of spiral galaxies.

2. How is objective classification of spiral galaxies different from subjective classification?

Objective classification of spiral galaxies involves using quantitative measurements and statistical analysis to categorize galaxies, while subjective classification relies on visual examination and personal interpretation. Objective classification is considered more reliable and unbiased compared to subjective classification.

3. What are the criteria used for objective classification of spiral galaxies?

The criteria used for objective classification of spiral galaxies include the shape and structure of the galaxy's spiral arms, the size and brightness of the central bulge, and the overall size and shape of the galaxy. Other factors such as the presence of bars, rings, and dust lanes may also be considered.

4. How do scientists use objective classification of spiral galaxies in their research?

Scientists use objective classification of spiral galaxies to study the properties, evolution, and relationships between different types of galaxies. It also allows for the identification of rare or unusual galaxies that may provide new insights into the formation and evolution of the universe.

5. What are the limitations of objective classification of spiral galaxies?

Objective classification of spiral galaxies may not capture the full complexity and diversity of these galaxies, as it is based on a limited set of criteria and may not account for individual variations. Additionally, it may be difficult to distinguish between different types of spiral galaxies, leading to potential misclassifications.

Similar threads

A Advice needed for exposure time computation for galaxies
    • Astronomy and Astrophysics
Replies
2
Views
1K
I Why use velocity dispersion in Faber Jackson relation
    • Astronomy and Astrophysics
Replies
1
Views
1K
A Do Large Galaxies Exist Without Central Supermassive Black Holes?
    • Astronomy and Astrophysics
Replies
1
Views
2K
Has the Number of Galactic Revolutions Influenced Spiral Galaxy Formation?
    • Astronomy and Astrophysics
Replies
5
Views
2K
I Too Much Dark Matter In CEG Mrk 1216
    • Astronomy and Astrophysics
Replies
2
Views
2K
Are Flat, Coplanar Orbits Only Found in Spiral Galaxies?
    • Astronomy and Astrophysics
Replies
4
Views
2K
I Deur Gravitational self-interaction Doesn't Explain Galaxy Rotation Curves
    • Beyond the Standard Models
3
Replies
72
Views
5K
The most simple explanation for origination of spiral galaxies?
    • Astronomy and Astrophysics
Replies
4
Views
4K
Galactic & cosmological numbers
    • Astronomy and Astrophysics
Replies
4
Views
3K
Why do stars orbit around a spiral galaxy in a rosette shape?
    • Astronomy and Astrophysics
Replies
3
Views
3K

Hot Threads

Recent Insights

Back
Top