Starship Asterisk*

There was no public expression of outrage a few years ago when cannibalism was depicted in a television commercial for M&M brand candy. That gave the green light to astronomers.

[quote="alexpirie"]Just wondering if anyone else finds the anthropomorphization of physical processes as in galaxies eating one another and practicing cannabalism or losing a struggle as in today's APOD (11/27/08 Galaxies in the River) a little odd? For some reason this just struck me as peculiar for the first time...not sure what to suggest as an alternative, but maybe there is a more accurate way to describe what is going on for the benefit of the non-astronomers like myself.[/quote]
Speaking as an astronomer, it certainly does not bother me. There is nowhere near enough room in an APOD caption to describe the process in rich scientific detail; putting a slightly poetic or literary spin on things is welcome (and science has a long history of doing just that, although it has fallen out of favor in recent decades). That said, it is important that the APOD captions also provide good links to sources providing more rigorous detail- something that they usually do.

For the layman:

As far as I know, when a small galaxy travels near a large galaxy, it can have one of four basic outcomes (each one the effect of gravity):

(1) The small galaxy's path, shape, and composition may be affected to some degree by the passage. The large galaxy's path, shape, and composition may be affected to a lesser degree. Their passage is relatively [b]fast and separated[/b], and after the passage they go off separately into space.

(2) The small galaxy's path, shape, and composition may be affected to some degree. The large galaxy's path, shape, and composition may be affected to a lesser degree. Their passage is at a relatively [b]moderate speed with moderate separation[/b], and the small galaxy goes into a roughly elliptical orbit around the large galaxy that may be stable for one to thousands of passes.

(3) The small galaxy's path, shape, and composition are affected greatly. The large galaxy's path, shape, and composition are affected more as the smaller galaxy spirals closer. Their passage is at a relatively [b]slow speed with small separation[/b]; the small galaxy spirals into the larger galaxy and merges into it as it does so.

(4) The small galaxy's path, shape, and composition are affected greatly. The large galaxy's path, shape, and composition are affected more as the smaller galaxy passes through. Their passage is at a relatively [b]high speed with small separation[/b]; the small galaxy passes through the larger galaxy and exchanges material as it does so.

In the case of today's APOD, I think we might be somewhere between (2) and (3).

For two galaxies of more equal size or more than two galaxies, the possible outcomes become more numerous, more complicated, and favor more large-scale deformation. Galaxies may pass through each other multiple times before they merge completely.

Galaxies exist in galaxy clusters. Each galaxy, except as perturbed by the gravity of other galaxies that pass by, pursues an independent elliptical path focused at the center of the galaxy cluster. Each elliptical path has a different size (and therefore a different orbital period and speed), has a different eccentricity (is more elongated or more circular), and is set at a different angle in a different plane, though they all are bound by their common gravity to the same center. As a result, galaxies can pass each other at all angles, each resulting in a unique outcome.

If that's too simplistic or not entirely correct, somebody please expand upon this.

---

And what's with Judy's tooth?

Well...we are only human after all. We express things in terms that most people can grasp so that more people will understand what we are trying to say. There is likely several appropriate mathematical formulae that apply but most lay-people wouldn't gain a complete understanding of what was being said. We, being human, do tend to anthropomorphize our descriptions of processes because we want to be understood by the most people possible. Though I must agree, WRT galactic interractions, terms like canibalism would imply that all star systems are devoured in the process. It is more likely that 99+% of the stellar systems, globular clusters, and stellar clusters remain intact and relatively unscathed in the [i][b][u]assimilation[/u][/b][/i] process. Perhaps assimilation is a better term than canibalism.

Just wondering if anyone else finds the anthropomorphization of physical processes as in galaxies eating one another and practicing cannabalism or losing a struggle as in today's APOD (11/27/08 Galaxies in the River) a little odd? For some reason this just struck me as peculiar for the first time...not sure what to suggest as an alternative, but maybe there is a more accurate way to describe what is going on for the benefit of the non-astronomers like myself.

http://antwrp.gsfc.nasa.gov/apod/ap081127.html

[url=http://antwrp.gsfc.nasa.gov/apod/image/0811/NGC1532_gendler.jpg][img]http://j3000.com/x/apod/crop_apod_081127.jpg[/img][/url]

This is after some retouching.
Viewer caution: It might be false color.

[url=http://www.timelesstrinkets.com/SixtiesSeventies/Images/JetsonsJudyPinkCar.jpg][img]http://www.timelesstrinkets.com/SixtiesSeventies/Images/JetsonsJudyPinkCar.jpg[/img][/url]

It's really cultural icon Judy Jetson in her pink car.
We can still resolve a little more detail out of this photo.

[url=http://www.wattpoultry.com/uploadedImages/Watt_Poultry/Poultry_USA/Feature_Articles/0710USAnatural_turkey.jpg][img]http://www.wattpoultry.com/uploadedImages/Watt_Poultry/Poultry_USA/Feature_Articles/0710USAnatural_turkey.jpg[/img][/url]

Too far, but this [i]is[/i] the Thanksgiving APOD (on the US calendar).
Gobble, gobble.