Astronomy Question: APOD = Astronomy Picture of the Day The APOD { http://apod.n

Question

Astronomy Question:

APOD = Astronomy Picture of the Day

The APOD { http://apod.nasa.gov/apod/ap151119.html } for 2015 November 19 shows a detailed image of the nearby "peculiar elliptical" galaxy Centaurus A. This galaxy doesn't look like an elliptical to me! I thought elliptical galaxies are "red and dead". The explanation says that this galaxy is "forged in a collision of two otherwise normal galaxies", and contains "young blue star clusters" and "star-forming regions". Can you describe a simple scenario in which a collision might end up producing a galaxy that looks like this one?

Explanation / Answer

An elliptical galaxy is a type of galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile. Unlike flat spiral galaxieswith organization and structure, they are more three-dimensional, without much structure, and their stars are in somewhat random orbits around the center.

Here are two physical types of ellipticals; the giant ellipticals, whose shapes result from random motion which is greater in some directions than in others (anisotropic random motion), and the "disky" normal and low luminosity ellipticals, which have nearly isotropic random velocities but are flattened due to rotation.

Dwarf elliptical galaxies have properties that are intermediate between those of regular elliptical galaxies and globular clusters. Dwarf spheroidal galaxies appear to be a distinct class: their properties are similar to those of irregulars and late spiral-type galaxies.

Every massive elliptical galaxy is to contain a supermassive black hole at its center.The mass of the black hole is tightly correlated with the mass of the galaxy, via the M–sigma relation

When two spirals collide, they lose their familiar shape, morphing into the less-structured elliptical galaxies

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.