ASTR 110L Name:

Fall 2009

Nebulae, Star Clusters, and Galaxies — Fall Semester

Read: Ridpath pp. 267–269: star-forming nebulae & open clusters; pp. 276–281: planetary nebulae & supernova remnants; pp. 288–295: globular clusters & galaxies

Examples of emission nebulae: photos on p. 139, p. 184, p. 270, p. 279

Examples of reflection nebulae: photo on p. 242

Neighboring emission & reflection nebulae — see images of the Trifid Nebula:

(examples located at: http://astro.nineplanets.org/twn/n6514x.html )

Examples of planetary nebulae: photos on p. 220, p. 277

Examples of supernova remnants: photos on p. 138, p. 280

Open-cluster evolution: http://www.astronomynotes.com/evolutn/s9.htm

Skim: Ridpath pp. 269-276: stellar evolution

Also, see related sections of your ASTR 110A textbook (Bennett).

OBSERVATIONS with telescopes:

(10 to 20 pts.) For each of the faint objects that you are able to observe, make a pencil-sketch (use shading, not just line-drawing) and some observing notes.

Open Clusters:

In the field, make some notes about each object’s...

a. Total/overall apparent brightness, relative to the other clusters

b. Overall apparent size, relative to the other clusters

c. Is the cluster relatively dense, tight, or unresolved (at its center); or relatively open, loose, or extended?

d. Any detectable color, of entire cluster overall, or of individual stars in cluster

e. Any other distinguishing features, shape, relative number of stars, etc., that you notice

f. Sketches are optional, since it is particularly difficult to sketch a star cluster. But if you wish, feel free!

Later, look up each open cluster’s distance, in light-years (in Ridpath).

Globular Clusters, Nebulae, & Galaxies:

In the field, for each object...

a. Record its name.

b. Identify the type of object.

c. Sketch it.

d. Record any additional observing notes (apparent color? overall shape? number of stars (look in Ridpath)? stars clustered densely or sparsely? any other distinguishing features?).

Later, look up each object’s distance, in light-years (in Ridpath).

FOLLOW-UP at home:

On an attached sheet, briefly answer the following 6 questions:

1. (4 pts.) What is the difference between an emission nebula, a reflection nebula, and a planetary nebula? What causes each, and/or what makes each type of nebula glow? What are their typical colors (usually noticeable only if you were to take a long photograph, but not by eye with our telescopes)?

2. (4 pts.) What is the difference between an open cluster and a globular cluster? How do they look different from each other? Where in the Milky Way Galaxy (and hence, in the sky) would you expect each type of cluster to be most commonly located?

3. (3 pts.) Approximately how far from Earth is the center of our Milky Way Galaxy, in light-years? Were tonight’s objects that we observed closer to us or farther from us than the center of the Milky Way is? Were tonight’s observing targets located only in our “neighborhood” of the Milky Way, or were they distributed throughout the Milky Way? How do you know (i.e., how big is the Milky Way, compared to these objects’ distances from Earth)?

4. (4 pts.) Approximately, what are typical distances from Earth of open clusters vs. globular clusters vs. galaxies? Approximately, what are the typical numbers of stars that comprise open clusters vs. globular clusters vs. galaxies? From what you observed, do the two factors counter-balance each other, so that all three types of objects appeared to have similar brightness to us, observing from Earth?

5. (3 pts.) Should open clusters’ overall apparent brightness have any correlation with their distance from Earth? Should open clusters’ apparent density/openness have any correlation with their distance from Earth? Does this agree with your observations? Might either total brightness or density be affected by factors other than distance? If so, what?

6. (2 pts.) Should open clusters’ color (either overall, or of individual stars) have any correlation with their age? Should the clusters with many blue stars be relatively young or relatively old? When should a cluster start exhibiting some orange or red giants: immediately upon formation, or after aging for a while? (You may need to look up some information to answer this.) Does this agree with your observations (and the ages provided for you in chart)?

Open Clusters

• OBJECT NAME • DISTANCE • TYPE OF OBJECT • ADD’L COMMENTS	SKETCH (most open clusters are hard to sketch… you can make observing notes instead)
NGC 6530 cluster & overlapping nebula M8 = Lagoon Nebula (in Sagittarius) age ≈ 2 million years distance:	do sketch this one!
NGC 6231 (in Scorpius) age ≈ 5 million years distance:
M6 (in Scorpius) age ≈ 40 million years distance:
M11 = Wild Duck Cluster (in Scutum) age ≈ 150 million years distance:
M7 (in Scorpius) age ≈ 200 million years distance:

Globular Clusters

• OBJECT NAME • DISTANCE • TYPE OF OBJECT • ADD’L COMMENTS	SKETCH
M4 (in Scorpius) distance:
M22 (in Sagittarius) distance:

Nebulae

• OBJECT NAME • DISTANCE • TYPE OF OBJECT • ADD’L COMMENTS	SKETCH
M17 = Omega or Horseshoe or Swan Nebula (in Sagittarius) distance:
M27 = Dumbbell Nebula (in Vulpecula) distance:
M57 = Ring Nebula (in Lyra) distance:

Galaxies

• OBJECT NAME • DISTANCE • TYPE OF OBJECT • ADD’L COMMENTS	SKETCH
M31 = Andromeda Galaxy (in Andromeda) & little companion galaxies M32 & M110 distance:

More Open Clusters

• OBJECT NAME • DISTANCE • TYPE OF OBJECT • ADD’L COMMENTS	SKETCH
h and c Persei = NGC 869 and NGC 884 (in Perseus) age ≈ 10 million years (both) distance:
M45 = The Pleiades = Na Makali‘i = Subaru (in Taurus) age ≈ 75 million years distance:
The Hyades (in Taurus — use binoculars) age ≈ 800 million years distance:

NOT USED:

c. (2 pts.) What are the 4 main classifications of shapes (“morphologies”) of galaxies? (Hint: E, S, SB, and Irr… but give the full names of these categories.) If we observe any galaxies in the field: Were you able to notice any difference between these shapes using our 8-inch Dobsonians? If not, why do you think not?