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The Milky Way and the Andromeda galaxy are predicted to collide in about 4 billion years. Notice in the simulation that the two galaxies pass through each other, move a bit apart and then collide again in a series of “bounces” until they completely merge. The expectation is that this collision wouldn’t affect the solar system much, and that it is unlikely that any two stars would collide. Of course, by then the Sun will have expanded and it is unlikely that there would be anything alive on Earth to witness any of it!

complete the

Galaxy analysis report

Galaxy analysis
Introduction to galaxies
Galaxies are large structures containing stars, interstellar gas and dust, and dark matter. A
single galaxy can have as few as a million stars for a dwarf galaxy or as many as a trillion (i.e. a
million of millions) for a giant elliptical galaxy. Stars and the other forms of matter that
comprise a galaxy are gravitationally bound together making a galaxy a single structure. The
diameters of galaxies range from about a thousand parsecs to few hundreds of thousands of
parsecs. Galaxies are important for many reasons. They are the building blocks of the largescale structure of the universe. By observing galaxies, astronomers can test theories about how
the universe began and how it evolves.
Figure 1. Types of galaxies
Traditionally, astronomers
have classified galaxies
according to their shape
classification). In figure 1
the three basic
morphological types of
galaxies are shown: the
spirals, the ellipticals and
the irregulars.
The most widely used, and somewhat more
detailed, is the Hubble classification scheme often
called the Hubble tuning fork (shown in figure 2).
In this scheme, various types of elliptical galaxies
are on the left. Their shape changes from round
spherical E0 type, through more oblate, to a
stretched, cigar-like, shape of E7 type. In the
middle of a class of galaxies known as lenticulars,
which are given the designator S0. Lenticular
galaxies have a large central bulge that is similar to
elliptical galaxies, but they also have a flat disk-like
region similar to spiral galaxies, though lacking the
spiral arms.
Branching away from the S0 galaxies are the spiral
galaxies. The top branch contains spiral galaxies
Figure 2. Hubble classification
arranged according to the size of the central bulge and the tightness of the spiral arms. These
types of galaxies are labeled Sa, Sb, and Sc in order from the tightest to the least tight. The
bottom branch contains spirals that have bars connecting the bulge to the arms. These types of
galaxies are labeled SBa, SBb, and SBc.
The Hubble classification scheme was developed by Edwin Hubble in the 1930s and it classified
any other galaxy that did not fit into one of the previously described types as simply “irregular”.
Since then, other schemes have been proposed adding additional spiral categories, a third
“fork”, irregulars and classifying dwarf galaxies.
Although appearances can
sometimes be deceiving,
Spiral galaxy: Whirlpool
typically, elliptical galaxies
galaxy: IC
contain proportionally less
gas than spirals and are
composed mainly of older,
redder stars with few if any
young blue stars because of
little or no ongoing star
formation. Spiral galaxies
tend to have proportionally
more gas and active star
NGC 4866
forming regions characterized
by hot blue stars, ruby red
ionization nebulae (these socalled H II regions are
Not to scale
produced when hot, blue,
young stars partially ionize
surrounding hydrogen gas, which then undergoes recombination and emits strongly at
hydrogen alpha 656 nm line) and blue reflection nebulae like that in the Pleiades cluster (as an
example see Tarantula Nebula in figure 4). But blue ellipticals and red spirals have also been
found. Irregular galaxies frequently exhibit violent ongoing star formation.
Figure 4. Tarantula Nebula (left) is part of
Milky Way’s dwarf neighbor galaxy
named Large Magellanic Cloud (LMC)
which can be seen with unaided eye in
the southern hemisphere’s sky (right).
The bright ruby spot to the left of the
bottom of the irregularly shaped LMC is
the Tarantula Nebula.
Introduction to citizen science
Citizen science or crowd sourcing is important to scientists who and have found that using
non-experts, citizens, to help sort and classify data is a valuable research tool. The original
galaxy zoo project simply asked people to classify galaxies into spiral or elliptical. Galaxy
Zoo has evolved into Zooniverse, a large number of projects in the sciences and social
sciences. Visit the Zooniverse site to see examples and take a look at the newest projects.
Volunteer value: During this lab you will be actually contributing to the scientific effort.
Do your best to make careful and accurate observations, but don’t stress over whether you
are “right”. Each image is viewed by several people and if an image is misclassified by one,
it is likely that others will sort it correctly. Sometimes something strange is in an image
and knowing that can also be highly useful. The most famous example is the “Voorwerp”.
Hanny’s Voorwerp is an unusual green blob spotted on one of the original galaxy zoo
images by a Dutch schoolteacher, Hanny van Arkel. She noticed the odd appearance of this
blob and noted it for researchers Astronomers are studying this and other similar images today
because she noticed something odd on a Galaxy Zoo image in 2007.
Figure 1
Even if you don’t observe something new and dramatic, as a volunteer you can help
scientists by sorting images to allow further study of those that a particular researcher will
use. Citizen science uses the human ability to see patterns to help analyze images that, at
least for now, are not easily analyzed by computer. Go to the “About” tab on the zooniverse
site to read more about why human volunteers are helping scientists explore vast amounts
of data that have been collected both recently and in sources such as ships logs, or old
astronomical images.
GMU’s contribution: In an original
edition of Galaxy zoo, a simulation
designed by astronomers at George
Mason allowed user to adjust things such
as size number of stars, velocity and
angle of impact for colliding galaxies.
They adjusted these parameters to try to
get a result from the simulation that
matched our images of real colliding
galaxies. An example of colliding galaxies
is this image from Astronomy Picture of
the day of NCG 4676, The Mice.
Astronomers expect a collision like this between the Milky Way and Andromeda as gravity
brings our galaxies together billions of years from now.
Though the collision simulation is now retired from the Zooniverse, it is a good example of
how simulations can advance knowledge in astronomy when combined with what we see
in actual images.
Figure 3: The Mice colliding galaxies from
astronomy picture of the day
Your assignment: In this lab you will both complete an assignment using real galaxy
images and do a little bit toward furthering our understanding of galaxies. Thank you!
Galaxy classification with Galaxy Zoo
Team members
Galaxy Zoo is a crowdsourced astronomy project which invites people to assist in the morphological
classification of large numbers of galaxies. It is an example of citizen science project as it enlists the help of
members of the public to help in scientific research. Galaxy Zoo is part of the Zooniverse, a collection of citizen
science projects.
Go to https://www.zooniverse.org/projects and look at the different projects that citizen-scientists can
become involved in via Zooniverse.
1. Which Zooniverse projects might interest you and why?
Look for the project labelled “Galaxy Zoo”. Make sure you find that exact name, there are several similar ones.
If you have hard time locating it, here is a link:
Click on “Research,” “Results,” and “FAQs” and read about the science involved in Galaxy Zoo and the origin of
the original Galaxy Zoo. Then answer the following questions:
2. Why is it useful to astronomers to have citizen scientists involved in this project (classifying shape, color,
presence of such things as bars and bulges and unusual features?
3. What are the sources of the images for Galaxy Zoo? Name at least five telescopes involved now or in the
4. How many galaxies have been thus far classified through Galaxy Zoo? (a ballpark figure will do)
Read the information, then click on “Profile” and create an account. Use your first and last name as a
username. You can classify the galaxies without an account, but you will not be able to get their images/info
back, which you’ll need in order to complete this lab. Once you have an account, read through the Field guide
(a menu on the right side of your screen) to get an idea of what to look for.
Click “Classify” and begin classifying. Be sure to check the “field guide” if you are not sure how to answer any
of the questions.
Classify at least 20 galaxies. Keep track of color: blue or red (red includes yellow and orange) and the shape of
these galaxies so that you can fill table 1. After completing the initial classification for all the galaxies, click on
“Recents” at the top of the page. This will present a list of thumbnail images for the galaxies that you
Below provide the screenshots or snips of all of the thumbnails for the galaxies that you classified You can do
this for all at once using the “Recents” choice on the upper left of the classification screen. Your account
username should be displayed as well.
5. Place the screenshots with thumbnails of all classified galaxies here:
Before going on, do the following counts: number of red ellipticals, red spirals, and red irregulars, number of
blue ellipticals, blue spirals, and blue irregulars, and the total numbers of ellipticals, spirals, and irregulars.
Record the tally in table 1.
Table 1. Fill in the table
From all the galaxies that you classified, choose one to investigate/describe in more detail. Click on the
thumbnail in Galaxy Zoo and look at the galaxy’s “Examine” page to see what information about it is provided.
Also look at the links to data bases with more information about the galaxy. Check those resources and find
out what extra information they contain. Then:
Here is some help in finding some of the information about each galaxy and
examples of what you might see.
The icons to the bottom right of the thumbnail allow you to get information,
“favorite” the image, add it to a collection, or get a higher resolution image of
the object.
Click on the information icon (a dark circle with and i inside) to get information about the
galaxy and more links to use to explore it. You will see its coordinates in the sky (ra and dec)
and links to surveys that might include it. Some of the links are easier to navigate than others,
but try them all to see what you can find (it may require drilling down several layers to see
something interesting).
If you go to the DECALS survey you might be able to check a box for the spectrum
of the object. If it has a measured spectrum, clicking the box will draw a circle
around the object of interest and when you click inside the circle you will get a
Spectrum .
Sloan Digital Sky Survey
spectrum for the galaxy
shown below.
6. Choose one of the most interesting galaxies and write a description. Your description should include as
many of the following as you can find:
a) a link to your galaxy on the Galaxy Zoo site
b) galaxy ID
c) its color (red or blue)
d) a full sized image (copy and paste it into the report)
e) the decisions you made while classifying this galaxy and what did you classify it as. To help you
back-track, in figure 5 you can see the decision tree for Galaxy Zoo and available choices.
f) other info available on the Galaxy Zoo site such as
• telescope
• survey
• right ascension and declination
• apparent and absolute magnitudes
• anything else provided (note: not all of the listed items are available for all galaxies)
g) linked data bases
h) follow the links to the data bases. What information do they contain? (Don’t worry about
understanding it all, just try to get a gist of what’ out there) See if any of the linked sites provide
a spectrum and if they do, copy it to your report. Then describe any of its features that you can
identify, such as emission, absorption lines, and the shape of the continuum. How does it
compare to the stellar spectra you studied?
i) describe any unusual features that the galaxy may have.
Galaxy description: Put the description of the galaxy you found interesting here, along with as much
of the relevant data about it you could find on Galaxy zoo and on the data bases that contain the
galaxy. This report should be at least half a page and be written in narrative style (paragraphs,
whole sentences, etc.!)
Conclusion Questions:
7. Did you find/see anything unusual?
8. Why is it important to have more than one person classify the shape and features of each galaxy in Galaxy
9. How would you resolve any discrepancies between classifications done by different users?
10. Do you think the public can make a meaningful contribution to astronomy or science in general through
projects like Galaxy Zoo and others from the Zooniverse?
Save a copy of your report in Word or PDF format, then submit on Blackboard.

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