GalaxyZoo_SuperNova1987a_Lab_15AUG23
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Course
107
Subject
Astronomy
Date
Dec 6, 2023
Type
docx
Pages
6
Uploaded by SuperHumanOxideBison32
Name:
Derek Greene
GS 107
Part I: CLASSIFYING GALAXIES
Galaxy Zoo has users classify galaxies found in the background of Hubble Space Telescope
images. By crowd-sourcing this task, scientists receive valuable data that computers alone cannot
process.
https://www.zooniverse.org/projects/zookeeper/galaxy-zoo/about/research
To begin, visit the “Classify” region of the Galaxy Zoo website at
https://www.zooniverse.org/projects/zookeeper/galaxy-zoo/classify
. Start with the Tutorial tab
and once done, go to the Task tab and you’ll be on your way.
While there are many features of galaxies to consider as you classify them, we’ll primarily be
considering if they are Smooth or if they are Features or Disk.
You should log the galaxies you classify in the table below.
Classify and log 25 galaxies.
Features or Disk
Smooth
17
8
1.
Sketch below one of the galaxies that had a feature or disk.
2.
Which type of galaxy occurs most often based on your data?
Features or Disk
3.
Which type of galaxy was easiest to classify?
Smooth
4.
What are some key chararistics of those galaxies which are harder to classify?
Primarily, galaxies that were very small or had irregularities.
5.
How representative do you think your data are of galaxies in general?
That is, do you
think a sample size of 25 is sufficient to get a good feel for the various types of galaxies?
No, I do not believe that a sample size of 25 would be sufficient to get a good feel for the
various types of galaxies
Part II: Supernova 1987a (SN1987a)
This image, along with the corresponding news release, can be found at
https://hubblesite.org/contents/media/images/2010/30/2768-Image.html?news=true
This was
taken with the Hubble Space Telescope (HST).
The James Webb Space Telescope will be
looking into this region in the near future as well.
https://www.inverse.com/science/supernova-
explosion-mystery-james-webb-telescope
Some general information can be found here:
https://chandra.harvard.edu/press/sn1987afact.html
The Wikipedia article has more detail:
https://en.wikipedia.org/wiki/SN_1987A
In the image of SN1987a shown above you can see two bright stars, plus a third star surrounded
by a bright ring of material (ignore the two dimmer rings further out). This ring was shed from
the outer layers of the blue supergiant star Sanduleak –69
o
202, millions of years prior to the
supernova explosion, as the star evolved from being a red supergiant.
The ring was not
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illuminated until a shock wave from the supernova arrived at the ring and caused the material in
it to heat up and emit light.
1.
Use a ruler to measure the diameter of the ring in millimeters which we will designate as D
ring
.
Make sure to measure the ring at its widest part because it is actually circular and you are
viewing it at an angle that causes it to appear more elliptical. Measure the width of the entire
image in millimeters as well which we will designate as L
image
. Record the diameter of the ring,
the radius of the ring and the image here.
D
ring
=
18
; R
ring
=
9
;L
image
=
133.096
.
2.
This image is 16.4 arcseconds wide. A ratio of the radius of the ring, R
ring
, and the image size,
L
image
, is equal to a ratio of the ring’s angular size,
, to the angular size of the image:
3.
Input your values for the width of the image and radius of the ring into the equation above to
find the angular size of the nebula,
. Report the value for
here:
1.10897397
4.
It turns out that for very small angles, we don’t need to use trig functions (i.e., sine, cosine
tangent).
This can save us a lot of math, particularly in complicated geometries.
We can
apply what is known as the small angle formula, presented below, to find the actual radius of
the nebula in kilometers. The distance from Earth to SN1987a, D, is 1.6 x 10
18
km and the
small angle formula gives us:
That 206,265 comes from a bunch of unit conversions which you could solve for yourself if
you needed to.
But you don’t need to do that here.
Report your value of R here:
8602323961893.68
5.
Let’s assume that the ring was shed with a velocity of about 20 kilometers per second outward,
as is typical of red supergiant winds. How long ago was this ring shed from the central star?
(Don’t forget to use the radius instead of the diameter for this calculation!)
430116198094.684
seconds ago
6.
The shock wave itself is not luminous enough to be seen optically in this image. Ultraviolet
spectroscopy was used shortly after the explosion to detect carbon IV transition spectral lines.
The rest wavelength, λ
0
, of carbon IV is 190.4 nanometers. The carbon IV line was recorded
with Doppler shift,
λ, of up to 19.6 nanometers. Using the Doppler equation,
find the velocity, v, of the shock wave and record this value here:
(Recall that c is the speed of light, 3 x 10
5
km/s.)
V= 30882.35294117
7.
Given the speed of the shock wave and the ring’s linear size, calculate how long it took the
shock wave to reach the ring after the explosion occurred.
~25 years
8.
The first pictures of the ring were taken in February 1998. How close was your estimate?
What are possible sources of any discrepancy?
My estimate was fairly close. Possible sources
for discrepancy include doppler shift.
9.
This is just here to visually see how the shockwave progressed over time.
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