ASTR1514lab12_2022
pdf
keyboard_arrow_up
School
The University of Oklahoma *
*We aren’t endorsed by this school
Course
1514
Subject
Astronomy
Date
Jan 9, 2024
Type
Pages
3
Uploaded by ChancellorFieldSpider5
Ind 8 - 15
Clock time: _____ Galaxies are very much like star clusters in that there are many stars all gravitationally bound
together. However, galaxies are essentially large
collections
of star clusters (existing and
ripped-apart ones) and have had more than one occurrence of star formation (i.e., not all of a
galaxy’s
stars formed at the same time while a
star cluster’s
stars DID form at the same time).
17.
Observe the set of galaxies on the screen. Which of the galaxies appear to be mostly blue?
(note: the word “blue” is used to also include the colors violet and white)
Record the number and classification (elliptical, spiral, merging) of those galaxies. Why do
you think these galaxies appear blue?
(note: think simple here – “age” shouldn’t be in the answer)
18.
Which of the galaxies appear to be mostly red? (note: the word “red” is used to also include
the colors orange and yellow) Record the number and classification (elliptical, spiral,
merging) of those galaxies. Why do you think these galaxies appear red?
19.
Which types of galaxies appear to have many young stars: elliptical, spiral, or both?
Explain your reasoning.
(hint: think of the life spans of the different kinds of stars and the
colors thereof)
20.
Could the mostly blue galaxies that you identified in Question #17 also contain old stars?
Explain your reasoning.
Be careful here –
don’t think that galaxies that contain many young stars (spirals) are overall
younger than ellipticals – spirals ALSO have lots of old stars and ARE old, it’s just that, for
whatever reason, spirals still have material to keep making NEW stars and ellipticals don’t.
Ind 8 - 16
Clock time: _____ Dust in Galaxies:
Besides stars, galaxies sometimes also contain dust. This dust produces dark bands across, or
patches in, the galaxy.
21.
Which of the galaxies show evidence of dust (dark, obstructed patches)? Record the
number and classification (elliptical, spiral, merging) of these galaxies.
Gas and Star Formation in Galaxies:
In addition to stars and dust, galaxies may also contain gas. Gas and dust are usually found
together but gas is not often seen using visible light wavelengths.
22.
Would you say that a galaxy that is experiencing active star formation contains little gas or
abundant gas? Explain your reasoning.
23.
Which type of galaxy (elliptical or spiral) appears to have abundant gas available? Note
that gas and dust generally exist together. Explain your reasoning.
24.
Which type of galaxy (elliptical, spiral, both, or neither) is likely to contain both many
O-spectral type stars as well as many M-spectral type stars? Explain your reasoning.
25.
Which type of galaxy (elliptical, spiral, both, or neither) is likely to contain many M-spectral
type stars but very few (if any) O-spectral type stars? Explain your reasoning.
26.
Which type of galaxy (elliptical, spiral, both, or neither) is likely to contain only O-spectral
type stars? Explain your reasoning and then check with your TA.
Ind 8 - 17
Clock time: _____ 27.
Consider the discussion among three students about a galaxy that appears red.
Student 1:
Because there is only red light in this galaxy and no blue light, I think that
only small, red stars formed in this galaxy and not any big blue ones.
Student 2:
I disagree; it’s just that blue stars don't last very long. I think the blue stars
that may have been there in the past have already evolved into red giants, so
the galaxy looks red due to the light from all the red giants.
Student 3:
Wait a minute; I think you are both wrong. I thought that both blue stars and
red giants live short lives (we saw that in Q15), so they should both be gone. I
think that all the blue stars that formed early on have evolved into the little
red stars that are there now. So the galaxy appears red because it’s full of a
lot of old red stars that used to be the blue stars.
Do you agree or disagree with any or all of the students? Why are the wrong parts wrong?
28.
Some scientists have imagined the
“tuning fork diagram” (shown at
right) as representing an evolutionary
sequence for galaxies, with galaxies
starting off as elliptical and
developing more structure over time.
Do you think this proposed
evolutionary sequence is correct?
Why or why not?
Check your answer with the TA.
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
- Access to all documents
- Unlimited textbook solutions
- 24/7 expert homework help