Cosmology: our galaxy is an oddball (Introduction)

by David Turell , Thursday, October 19, 2017, 19:43 (2591 days ago) @ David Turell

Our galaxy is different from the others we observe. Our solar system differs from others. Our Earth is not like other planets. And we live here to see all of this:

https://www.newscientist.com/article/2150955-why-our-freakish-galaxy-has-got-cosmologis...

"The Milky Way remains the prime example of such cosmic populations, with astronomers able to map, in detail, the stars, gas and dust that circle the supermassive black hole at its heart. This remains central to ideas of galaxy evolution. But while many of its observed properties agree with expectations, a number do not. Prominent on this list is the population of dwarf galaxies that accompany the Milky Way in space.

"Hints of oddness have been building for years. At the end of the 1990s, theoretical models predicted that our galaxy should have thousands of orbiting dwarf galaxies, but far fewer were seen. This problem came with another: the apparent lack of large satellite galaxies orbiting the Milky Way. Astronomers concluded that the complexities of star formation in the early universe could have messed up the formation process, resulting in what we see today.

"More recently, the small number of accompanying dwarfs and the Milky Way’s companion galaxy, Andromeda, were found to lie on well-defined planes, again at odds with theoretical expectation. The physics of gas in the early universe cannot account for these, with some questioning our underlying ideas of galaxy evolution.

"Now comes the latest blow. The Satellites Around Galactic Analogs (SAGA) Survey, has muddied the waters even further, showing that the dwarf galaxies orbiting Milky Way-like galaxies beyond our group of galaxies are actively forming new stars, while our own dwarfs appear to be sedately ageing with no new stars.

"Does this mean that our local environment is somehow quiet, and not representative of the wider universe? That observations of our backyard have little to say about the vast bulk of the cosmos?

"It is too early to say for sure, but we are increasingly faced with a dilemma, as our telescopes will continue to reveal distant galaxies in more detail, and it is likely that each will be, in some way, peculiar.

"Hints of oddness have been building for years. At the end of the 1990s, theoretical models predicted that our galaxy should have thousands of orbiting dwarf galaxies, but far fewer were seen. This problem came with another: the apparent lack of large satellite galaxies orbiting the Milky Way. Astronomers concluded that the complexities of star formation in the early universe could have messed up the formation process, resulting in what we see today.

"More recently, the small number of accompanying dwarfs and the Milky Way’s companion galaxy, Andromeda, were found to lie on well-defined planes, again at odds with theoretical expectation. The physics of gas in the early universe cannot account for these, with some questioning our underlying ideas of galaxy evolution.

"Now comes the latest blow. The Satellites Around Galactic Analogs (SAGA) Survey, has muddied the waters even further, showing that the dwarf galaxies orbiting Milky Way-like galaxies beyond our group of galaxies are actively forming new stars, while our own dwarfs appear to be sedately ageing with no new stars.

"Does this mean that our local environment is somehow quiet, and not representative of the wider universe? That observations of our backyard have little to say about the vast bulk of the cosmos? (my bold)

"It is too early to say for sure, but we are increasingly faced with a dilemma, as our telescopes will continue to reveal distant galaxies in more detail, and it is likely that each will be, in some way, peculiar."

Comment: The issue is whether we are a specially different galaxy to allow life. We're here and this may be the reason. God at work? A quiet neighborhood protects life. Note my bold.