Astronomy 107: Lab #7-Galaxies When viewed through backyard telescopes, galaxies
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Question
Astronomy 107:
Lab #7-Galaxies When viewed through backyard telescopes, galaxies appear as fuzzy patches, often very cotton-like. Most galaxies contain billins or trillions of stars. Galaxies come in three types: spiral, elliptical, and irregular. 1) Using Google Images or another reliable source, find an example of an elliptical, spiral, and irregular galaxy and fill-in the information below: Hubble's Categories M number or NGC number Galaxy Characteristics (What characteristics can you use to distinguish one type of galaxy from the others?) M 49 Elliptical M 31 Spiral Irregular Physical characteristics of a galaxy can tell us much about its stars. We can deduce the age of stars, the presence or absence of dust, and the presence or absence of gas and star formation. 2) Which of the galaxies appear to be red? Why do you think these galaxies appear red?Explanation / Answer
1. Elliptical galaxies are smooth and somewhat symmetrical with no distinctive arms. Fuzzy blob-like shaped with a central bright spot.
Spiral galaxies have distinct bright spiral arms with a bright spot.
Irregular shaped galaxies have no shape and arms, they seem like a glowing irregular cloud
2. The elliptical galaxies appear to be red because they contain much older hence red stars. Old stars have lower surface temperature hence they are red.
3. Spiral galaxies. Because they have many formatting young stars in them.
4. Spiral galaxies.
5. Yes, in the central region the stars have a reddish glow which happens for the old star population (globular clusters)
6. Spiral galaxies show clear evidence of gas and dust.
7. Stars form from the collapsing dust clouds. So yes it'll contain abundant gas.
8. As the spiral galaxy appears blue, has dark lines across, contain new stars, so it would have abundant gas available.
9. Spiral galaxies contain both O and M type stars. M type stars are common for all galaxies. As spirals have only active star formation so it has O types stars.
10. Ellipticals are made up of the cooler main sequence M type stars. Because they have no active star formation for the deficiency of gas.
11. Spirals, because they have abundant gas and active star formation.
12. Sa - M33 - Spiral, has a central bulge and spiral arms.
E0 - M87 - Elliptical, faint glowing central part in the middle.
Irr - NGC 1427A - Irregular shaped galaxy.
13.
As elliptical galaxies mostly contain old red stars and a little gas, so it cannot evolve into young star and gas filled spiral galaxies. So the sequence is incorrect.
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