APOD: M31: The Andromeda Galaxy (2016 Dec 27)

[APOD Robot]

M31: The Andromeda Galaxy

Explanation: What is the nearest major galaxy to our own Milky Way Galaxy? Andromeda. In fact, our Galaxy is thought to look much like Andromeda. Together these two galaxies dominate the Local Group of galaxies. The diffuse light from Andromeda is caused by the hundreds of billions of stars that compose it. The several distinct stars that surround Andromeda's image are actually stars in our Galaxy that are well in front of the background object. Andromeda is frequently referred to as M31 since it is the 31st object on Messier's list of diffuse sky objects. M31 is so distant it takes about two million years for light to reach us from there. Although visible without aid, the featured image of M31 is a digital mosaic of several frames taken with a small telescope. Much about M31 remains unknown, including exactly how many billions of years it will before it collides with our home galaxy.

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[heehaw]

I discovered M32, myself. Of course it was not an original discovery; I was about 14 years old and trying out my new Skyscope on Andromeda. It was pleasing to discover it, though! It doesn't seem to have changed over the years - same old M32!

[Roneflan@gmail.com]

I watched a documentary last night on black holes. M31, according to the documentary, has an inactive black hole at it's center. Do black holes reactivate and eventually consume all the stars and other "dust" in its galaxy?

[Chris Peterson]

I watched a documentary last night on black holes. M31, according to the documentary, has an inactive black hole at it's center. Do black holes reactivate and eventually consume all the stars and other "dust" in its galaxy?

Supermassive black holes appear to go through cycles of activity and passivity. But they are not capable of consuming more than a tiny fraction of the material in a galaxy.

[Frank999]

Whenever I see a picture of a galaxy I always like to think that somewhere in the picture, though obviously too small to see, there are ships travelling between the stars.

[Guest]

I watched a documentary last night on black holes. M31, according to the documentary, has an inactive black hole at it's center. Do black holes reactivate and eventually consume all the stars and other "dust" in its galaxy?

Supermassive black holes appear to go through cycles of activity and passivity. But they are not capable of consuming more than a tiny fraction of the material in a galaxy.

Come on. Gravity is gravity. It does not turn on and off. To suggest otherwise is just a display of ignorance. The black hole at the center of a galaxy if just a garbage collection system for everything that falls inwards. The mass of the galaxy is what holds it together.

[Chris Peterson]

I watched a documentary last night on black holes. M31, according to the documentary, has an inactive black hole at it's center. Do black holes reactivate and eventually consume all the stars and other "dust" in its galaxy?

Supermassive black holes appear to go through cycles of activity and passivity. But they are not capable of consuming more than a tiny fraction of the material in a galaxy.

Come on. Gravity is gravity. It does not turn on and off. To suggest otherwise is just a display of ignorance. The black hole at the center of a galaxy if just a garbage collection system for everything that falls inwards. The mass of the galaxy is what holds it together.

Why would you expect so much stuff to fall inwards? It doesn't. Massive bodies orbit a black hole. Only bodies that get very, very close can lose energy, either to drag from gas and dust or to gravitational radiation, and spiral inwards until their orbits intersect the event horizon.

[MarkBour]

I watched a documentary last night on black holes. M31, according to the documentary, has an inactive black hole at it's center. Do black holes reactivate and eventually consume all the stars and other "dust" in its galaxy?

Supermassive black holes appear to go through cycles of activity and passivity. But they are not capable of consuming more than a tiny fraction of the material in a galaxy.

Come on. Gravity is gravity. It does not turn on and off. To suggest otherwise is just a display of ignorance. The black hole at the center of a galaxy if just a garbage collection system for everything that falls inwards. The mass of the galaxy is what holds it together.

You mis-interpreted the statement about "cycles of activity and passivity". The gravity is always there, of course. What Chris is talking about is that only "occasionally" does any serious amount of material fall into the black hole (or at least gets shredded by it). Only in those periods when that is happening, does a black hole appear "active". See http://www.einstein-online.info/spotlights/bh_xray for more info.

[cheggers]

I was out earlier this evening looking at M31 with my favorite binoculars. The notion that our Milky Way galaxy will merge with Andromeda in about 4 billion years is fascinating. I hope humanity can somehow survive and evolve to be a part of the new Milkomeda or Milkdromeda.

[neufer]

The notion that our Milky Way galaxy will merge with Andromeda in about 4 billion years is fascinating. I hope humanity can somehow survive and evolve to be a part of the new Milkomeda or Milkdromeda.

• Oh (...yeah) "the humanity" (...Like self replicating ANDROids of Milkomeda perhaps )

An android is a humanoid robot or synthetic organism designed to look and act like a human, especially one with a body having a flesh-like resemblance.

The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch. During this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes.

[b][color=#0000FF]Human chromosome 2[/color][/b]

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<<Chromosome 2 is the second-largest human chromosome, spanning more than 242 million base pairs (the building material of DNA) and representing almost 8% of the total DNA in human cells. Chromosome 2 likely contains 1,491 genes, including those of the HOXD homeobox gene cluster.

All members of Hominidae except humans, Neanderthals, and Denisovans have 24 pairs of chromosomes. Humans have only 23 pairs of chromosomes. Human chromosome 2 is a result of an end-to-end fusion of two ancestral chromosomes.

The evidence for this includes:

The correspondence of chromosome 2 to two ape chromosomes. The closest human relative, the chimpanzee, has near-identical DNA sequences to human chromosome 2, but they are found in two separate chromosomes. The same is true of the more distant gorilla and orangutan.

The presence of a vestigial centromere. Normally a chromosome has just one centromere, but in chromosome 2 there are remnants of a second centromere in the q21.3–q22.1 region.

The presence of vestigial telomeres. These are normally found only at the ends of a chromosome, but in chromosome 2 there are additional telomere sequences in the q13 band, far from either end of the chromosome.

According to researcher J. W. IJdo, "We conclude that the locus cloned in cosmids c8.1 and c29B is the relic of an ancient telomere-telomere fusion and marks the point at which two ancestral ape chromosomes fused to give rise to human chromosome 2."