OBJECTS IN THE MILKY WAY
JASON KENDALL, WILLIAM PATERSON UNIVERSITY
1. Matching
First, go to this web page: http://jasonkendall.com/WPU/MWO/
There is a big list of objects on that web page. Your task is to match the object on the web page above
with its name on the table below. Four have already been done for you. After you’ve done that, then there
are questions based on the appearance of the objects in the various filters.
First, match the name to the list of objects on the Big List at the bottom of this page. Then determine
the type of object it is from this list of nine. You may use AAO and NOAO websites below to help you
determine which objects are which.
The Big List below comes from the Palomar Digital Sky Survey, which you can learn about here:
http://gsss.stsci.edu/SkySurveys/SkySurveys.htm
The Palomar Digital Sky Survey should be used to find the matches. You’ll need to use other resources to
determine the type of object. Each object was imaged with a blue filter, a red filter, and an infrared filter,
as well as a photographic emulsion that would be sensitive. All of the images below are one degree on a
side. Each image is unique. It is a process of elimination to discover the type of object. You’ll also notice
that in some filters, the object is brighter than in others. That appearance will be a clue to the object’s
nature. For instance, notice that M1 is bright in all three filters, but the Pelican is distinctly not. When
you compare M38’s three images, one is brighter, showing the stars more clearly. Noticing these differences
will be important for the other parts of this laboratory exercise.
• Go to http://archive.stsci.edu/cgi-bin/dss form
• Enter the object name in the field and click GET COORDINATES.
• The object now appears in TARGET.
• For each of POSS2/UKSTU (Red, Blue, IR), do these three steps:
– Change the height and width to 60 arcminutes.
– Change the file format to GIF.
– Right click on Retrieve Image, so it goes into a new tab.
• Compare these images you just retrieved to the images in the Big List on the MWO website, and
match the number of the Big List to the name.
Once you know which one it is on the list, look up what kind of thing it is and choose from the following
Object Types. Use the public image galleries in the following section to help you with that.
Emission Nebula
Planetary Nebula
Reflection Nebula
Open Cluster
Dark Nebula
Black Hole
Bok Globule
Globular Cluster Supernova Remnant Wolf Rayet star
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JASON KENDALL, WILLIAM PATERSON UNIVERSITY
2. The Three Big Lists
There are 80 objects, with four of them done for you for examples.
Name
Number on web page
Type of object
Other names or descriptions
#121
Emission Nebula
The Pelican Nebula
#140
Supernova Remnant
The Crab Nebula
#111
Open/Galactic Cluster
The Starfish Cluster
#134
Globular Cluster
no special name
Barnard 68
Barnard 163
Cone Nebula
Cygnus X-1
IC 434
IC 1396
IC 1805
IC 1848
IC 4604
IC 5070
IC 5146
L977
Messier 1
Messier 2
Messier 3
Messier 8
Messier 13
Messier 16
Messier 17
Messier 20
Messier 29
Messier 35
Messier 36
Messier 38
Messier 39
Messier 41
Messier 53
OBJECTS IN THE MILKY WAY
Name
Messier 57
Messier 62
Messier 67
Messier 75
Messier 79
Messier 80
Messier 92
NGC 40
NGC 246
NGC 281
NGC 457
NGC 663
NGC 752
NGC 869
NGC 896
NGC 1360
NGC 1973
NGC 1980
NGC 2024
NGC 2237
NGC 2254
NGC 2261
NGC 2264
NGC 2281
NGC 2301
NGC 2359
NGC 2392
Number on web page
Type of object
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Other names or descriptions
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JASON KENDALL, WILLIAM PATERSON UNIVERSITY
Name
NGC 2736
NGC 2808
NGC 3242
NGC 4361
NGC 5139
NGC 5694
NGC 6541
NGC 6543
NGC 6709
NGC 6811
NGC 6826
NGC 6883
NGC 6888
NGC 6910
NGC 6934
NGC 6960
NGC 6992
NGC 7000
NGC 7008
NGC 7009
NGC 7023
NGC 7243
NGC 7293
NGC 7635
NGC 7686
NGC 7789
Number on web page
Type of object
Other names or descriptions
OBJECTS IN THE MILKY WAY
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3. Analysis of the Images
3.1. Preliminary: Public Image Galleries.
• You’ll be using these later in the exercise for helping you answer some questions.
• NOAO: http://www.noao.edu/image gallery/
• AAO: http://203.15.109.22/images/
• Gemini: http://www.gemini.edu/gallery/v/astronomical images and illustrations/
• ESO: http://www.eso.org/public/images/
• Keck Observatory: http://www.keckobservatory.org/gallery/
• Hubble Space Telescope: http://hubblesite.org/gallery/
• New AAO: http://www.aao.gov.au/images/
• SEDS: http://spider.seds.org/ngc/ngc.html
• NGC Project: http://www.ngcicproject.org
• Other: http://cseligman.com/text/atlas/ngc10.htm
• More help: https://www.youtube.com/watch?v=m0Fa7-qvbCE
4. The Questions for this Activity
4.1. The filters that were used for these images.
(1) All of the images you looked at in Part 1 were taken photographically. This means that the photographic paper itself also figured into the process of taking pictures. All of your pictures came from
the Second POSS Please visit this website: http://gsss.stsci.edu/SkySurveys/Surveys.htm
• Name the emulsion and filter combo for the Blue images you studied.
• Name the emulsion and filter combo for the Red images you studied.
• Name the emulsion and filter combo for the Infrared images you studied.
(2) Each of the emulsion/filter combinations has a bandpass. Click on the link for each. Find the range
of allowed wavelengths for each filter/emulsion combination. Notice that the graph shows wavelength
across the X-axis and percentage of light passed on the Y-axis. It ranges from 0 to 1, where 1 is
100% transmission of light. Find the wavelength range where it passes at least 20% of the light.
• List the transmission range for the Blue filter/emulsion combo.
• List the transmission range for the Red filter/emulsion combo.
• List the transmission range for the Infrared filter/emulsion combo.
(3) Given the two questions above and the fact that they were used and documented in such detail, what
is the purpose of an astronomical color filter?
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JASON KENDALL, WILLIAM PATERSON UNIVERSITY
4.2. Open/Galactic Clusters.
(1) List three Open/Galactic Clusters from the Big List. (Give the Big List numbers...)
(2) In which filters are they the brightest?
(3) In which filters are they the dimmest?
(4) What kinds of stars are most prominent in these clusters?
(5) Compare and contrast the appearance of the clusters in the three filters. How are they different?
How are the same?
(6) How does the brightness of the stars in the different filters relate to the nature of the stars themselves?
4.3. Globular clusters.
(1) List three Globular Clusters from the Big List. (Give the Big List numbers...)
(2) In which filter are they the brightest?
(3) In which filter are they the dimmest?
(4) What are the kinds of stars make up these kinds of clusters?
(5) Compare and contrast the appearance of your three globular clusters in all three filters. How are
they different? How are the same?
(6) How does the brightness of the stars in the different filters relate to the nature of the stars themselves?
4.4. Clusters compared.
(1) Compare and contrast the appearance of the globular clusters versus the open/galactic clusters. How
are they different? How are the same?
(2) Look up three of the open clusters and three of the globular clusters in the NOAO and AAO websites
to check their color appearance. List them and describe the colors of the stars in the six clusters.
4.5. Emission Nebulae.
(1) List three emission nebulae from the Big List. (Give the Big List numbers...)
(2) In which filter are they the brightest?
(3) In which filter are they the dimmest?
(4) Look them up in the AAO and NOAO public image galleries. Attach those images to this report.
What are the characteristic colors in most images?
(5) In optical light images, what processes makes the red glow?
(6) In optical light images, what process makes the blue glow?
4.6. Actions on the Interstellar Medium (ISM).
(1) Define Stromgren Sphere.
(2) Find a nebula from the Big List that shows a Stromgren Sphere. (Give the Big List number...)
(3) Use Google and find the diameter of the Stromgren Sphere.
(4) How many times bigger is it than our Solar System?
OBJECTS IN THE MILKY WAY
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4.7. Interstellar Reddening.
(1) Define interstellar reddening.
(2) List an object from the Big List that clearly demonstrates interstellar reddening.
(3) For the next question, don’t use the low-resolution test images on the MWO web page. Instead,
obtain the high-resolution images in Blue, Red and IR for your object using the DSS. Make sure
you’ve chosen 60x60 for the size. Zoom in on the object to see it up close.
(4) How does interstellar redding manifest itself in the Big List images in Blue/Red/IR? That is, how
do you know it’s in the one you chose?
4.8. Planetary Nebulae.
(1) List two planetary nebulae from the Big Lists below.
(2) Compare the BLUE, IR and RED images of these objects and comment on their appearance.
(3) How do they differ in appearance the other emission nebulae? Give direct examples from the Big
List.
(4) Look up the two planetary nebulae in the AAO or NOAO websites.
(5) How do the Big List images compare with what you find on the NOAO, AAO and Wiki/Google
images for these objects?
(6) A planetary nebula is a type of emission nebula, so why do they look so different both in shape on
the images and in brightness in the three filters?
4.9. Supernova Remnants.
(1) List the supernova remnants in the Big List.
(2) Describe the appearance in all three filters, how the images differ and how they are the same.
(3) What is the reason for the differences in appearance?
(4) A supernova remnant is a type of emission nebula, so why do they look so different both in shape
on the images and in brightness in the three filters?
4.10. The physical size of an object.
(1) Choose one of the objects and google its distance and physical size. Some of them will be easier to
do than others.
(2) Now we shall verify it by computation.
(3) Look at its images in the Big List, and estimate the angular size of the object from its width on the
picture. All of them were taken with the WIDTH and HEIGHT set to 60 arcminutes. That means
that image is 3600 arcseconds by 3600 arcseconds in angular size, or one degree on a side. Which
means that 1/3600th of the image on a side is an arcsecond. From the definition of parallax, the size
of the object in AU divided by the distance the object in parsecs is the angular size of the object in
arcseconds. So, you may find the size in AU to be quite big.
(4) Use the small angle formula to determine the PHYSICAL size of the clusters. Show your work.
(5) How does the answer you calculated compare to the accepted value you found?
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JASON KENDALL, WILLIAM PATERSON UNIVERSITY
4.11. Acknowledgements for the images used in this exercise. It could not be created without the
huge work done by many many others.
The Digitized Sky Survey was produced at the Space Telescope Science Institute under U.S. Government
grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin
Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into
the present compressed digital form with the permission of these institutions.
The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology
with funds from the National Science Foundation, the National Aeronautics and Space Administration,
the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman
Kodak Corporation. The Oschin Schmidt Telescope is operated by the California Institute of Technology
and Palomar Observatory.
The UK Schmidt Telescope was operated by the Royal Observatory Edinburgh, with funding from the UK
Science and Engineering Research Council (later the UK Particle Physics and Astronomy Research Council),
until 1988 June, and thereafter by the Anglo-Australian Observatory. The blue plates of the southern Sky
Atlas and its Equatorial Extension (together known as the SERC-J), the near-IR plates (SERC-I), as well
as the Equatorial Red (ER), and the Second Epoch [red] Survey (SES) were all taken with the UK Schmidt
telescope at the AAO.
All images labelled with NOAO are courtesy of National Optical Astronomy Observatory/Association of
Universities for Research in Astronomy/National Science Foundation
All images labelled with AAO copyrighted by the Australian Astronomical Observatory, with photographs
by David Malin.