+
Related Flashcards
Related Topics
Cards In This Set
| Front | Back |
|
How old are young galaxies?
|
0 to 3 billion years
|
|
How old are old galaxies?
|
Over 3 to 12 billion years old, or more...
Irregular galaxies are shown at the bottom of the chart....Spirals are above them....then ellipticals are shown at the very top.
|
|
Deep observations show us very distant galaxies as they were when?
|
as they were much earlier in time
|
|
The most distant galaxies that we observe have a "look back time" of about how long?
|
13 billion years, we are seeing them as they were when the universe was only about a billion years old.
|
|
Galaxies younger than a billion years old are extremely _____________
|
redshifted
|
|
Galaxies that are redshifted can only be observed using what?
|
Telescopes sensitieve to infrared light
|
|
The redshift of a galaxy allows us to put them on what?
|
a timeline of the universe
the beginning of the timeline was the Big Bang, and continues out to approximately 15 billion years or more
|
|
Pictues of the farthest galaxies show galaxies when?
|
in their childhood
|
|
Pictures of the nearest galaxies show what ?
|
mature galaxies as they appear today
|
|
We still cannot directly observe what?
|
the earliest galaxies
|
|
Our best models for galaxy formation assumes what 2 things?
|
1. Hydrogen and helium originally filled all of the space almost uniformly duirng the first million years
2. distribution of matter was not perfectly uniform - certain regiions started out with slightly higher density. Gravity of denser regions pulled in surrounding matter. (Nature and origin of density enhancements during the early universe is still a major myster in cosmoloby)
|
|
Denser regions in galaxies contracted forming what?
|
Protogalactic clouds
|
|
Many galaxies may have formed from what?
|
mergers of multiple protogalactic clouds
|
|
Hydrogen and helium gasses in protogalactic clouds formed what?
|
first generation stars which were probably quite massive - living and dying in just a few million years.
|
|
During the early part of a galaxy's life "what" kept much of the gas from forming into stars, allowing it to settle into the rotating disk?
|
supernova explosions
|
