Here's the latest folks!

[nbcnews.com]

very nice and interesting fact... thanks!

I know this is an astronomy post, but do you guys mind if I post some funny videos relating to astrophysics here (and no, they are not from TBBT, but from that far superiorly written show, Futurama!)?

That question aside, I've been doing some reading about the photoelectric effect (just started, so consider me at below the bottom rung of the ladder, about halfway up the ladder poles). I know that Einstein received his Nobel prize for the photoelectric effect, but did you know that Heinreich Hertz was the first one to observe it back in 1887?

From Wikipedia -

Galaxy collision

Merging galaxies in the distant Universe through a gravitational magnifying glass.[2]
Colliding galaxies are common during galaxy evolution.[3] The extremely tenuous distribution of matter in galaxies means these are not collisions in the traditional sense of the word, but rather gravitational interactions.

Colliding may lead to merging if two galaxies collide and do not have enough momentum to continue traveling after the collision. In that case, they fall back into each other and eventually merge into one galaxy after many passes through each other. If one of the colliding galaxies is much larger than the other, it will remain largely intact after the merger. The larger galaxy will look much the same, while the smaller galaxy will be stripped apart and become part of the larger galaxy. When galaxies pass through each other, unlike during mergers, they largely retain their material and shape after the pass.

Galactic collisions are now frequently simulated on computers, which use realistic physics principles, including the simulation of gravitational forces, gas dissipation phenomena, star formation, and feedback. Dynamical friction slows the relative motion galaxy pairs, which may possibly merge at some point, according to the initial relative energy of the orbits. A library of simulated galaxy collisions can be found at the Paris Observatory website: GALMER [4]

Gallery

Close encounter at IRAS 06076-2139.[5]

Interacting galaxies NGC 4302 and NGC 4298 both located 55 million light-years away.[6]

Galaxy NGC 6052 merging into a single structure.[7]

Galaxy pair Zw I 136.[8]

ESO 576-69 is believed to be the nucleus of a former spiral galaxy.[9]

The Whirlpool Galaxy with its satellite NGC 5195.

The Mice Galaxies.

File:Colliding Galaxies Create Active Galactic Nuclei.ogv
This simulation follows the collision of two spiral galaxies that harbour giant black holes.

NGC 3447 comprises a couple of interacting galaxies.[10]

Barred spiral galaxy NGC 1512 in the process of a lengthy merger with dwarf elliptical galaxy NGC 1510.

Galactic cannibalism

2MASX J16270254+4328340 galaxy has merged with another galaxy leaving a fine mist, made of millions of stars, spewing from it in long trails.[11]
Galactic cannibalism refers to the process in which a large galaxy, through tidal gravitational interactions with a companion, merges with that companion; that results in a larger, often irregular galaxy.

The most common result of the gravitational merger between two or more galaxies is an irregular galaxy, but elliptical galaxies may also result.

It has been suggested that galactic cannibalism is currently occurring between the Milky Way and the Large and Small Magellanic Clouds. Streams of gravitationally-attracted hydrogen arcing from these dwarf galaxies to the Milky Way is taken as evidence for the theory.

Galaxy harassment
Galaxy harassment is a type of interaction between a low-luminosity galaxy and a brighter one that takes place within rich galaxy clusters, such as Virgo and Coma, where galaxies are moving at high relative speeds and suffering frequent encounters with other systems of the cluster by the high galactic density of the latter. According to computer simulations, the interactions convert the affected galaxy disks into disturbed barred spiral galaxies and produces starbursts followed by, if more encounters occur, loss of angular momentum and heating of their gas.

The result would be the conversion of (late type) low-luminosity spiral galaxies into dwarf spheroidals and dwarf ellipticals.[12]

Evidence for the hypothesis had been claimed by studying early-type dwarf galaxies in the Virgo Cluster and finding structures, such as disks and spiral arms, which suggest they are former disk systems transformed by the above-mentioned interactions.[13] However, the existence of similar structures in isolated early-type dwarf galaxies, such as LEDA 2108986, has undermined this hypothesis[14][15]

Notable interacting galaxies
Name Type Distance
(million ly) Magnitude Notes
Milky Way Galaxy, LMC and SMC SBc/SB(s)m/SB(s)m pec 0 Satellites interacting with their primary
Whirlpool Galaxy (M51) SAc (SB0-a) 37 +8.4 Satellite interacting with its primary
NGC 1097 SB(s)bc (E6) 45 +9.5 Satellite interacting with its primary
NGC 2207 and IC 2163 SAc/SAbc 114 +11 galaxies going through the first phase in galactic collision
Mice Galaxies (NGC 4676A and NGC 4676B) S0/SB(s)ab 300 +13.5 galaxies going through the second phase in galactic collision
Antennae Galaxies (NGC 4038/9) SAc/SBm 45 +10.3 galaxies going through the third phase in galactic collision
NGC 520 S 100 +11.3 galaxies going through the third phase in galactic collision
NGC 2936 ? +12.9 ?
Future collision of the Milky Way with Andromeda
Main article: Andromeda–Milky Way collision
Astronomers have estimated the Milky Way galaxy, will collide with the Andromeda galaxy in about 4.5 billion years. It is thought that the two spiral galaxies will eventually merge to become an elliptical galaxy[16][17] or perhaps a large disk galaxy.[18]

Would they really join together - each losing its momentum? And then, would they then become "stationary?" Or would they pass through each other (because they're mostly empty space) and keep on each of their merry ways? But how would each's gravity act on the other's? Or that of each other's individual entities on the other's?