Tycho's Supernova Remnant

1
Tycho's Supernova Remnant
a ds9 activity
2
Stella Nova
INTRODUCTION On the evening of November 11, 1572,
Danish astronomer Tycho Brahe noticed a new, very
luminous object in the constellation Cassiopeia.
This object became bright enough (as bright as
Venus!) to be observed for several weeks during
the day. Over the next year and a half, it
dimmed by a factor of about 10,000 until it was
no longer visible to the naked eye, even at
night.
Tychos Uraniborg (castle of the
heavens)
Cassiopeia
3
If it were a star, then the immutable heavens
had changed, and the basic contrast between the
superlunary region and the corruptible earth was
in question. If it were a star, the earth might
more easily be conceived as a planet, for the
transitory character of terrestrial affairs would
now have been discovered in the heavens as well.
Brahe and the best of his contemporaries did
conclude that the visitor was a star.
Observations indicated that it could not be
located below the sphere of the moon or even
close to the sublunary region. Probably it was
among the stars for it was observed to move with
them. Another cause for cosmological upheaval had
been discovered. from The Copernican
Revolution, Thomas Kuhn
Tychos Stella Nova, however, was not the birth
of a star as he had thought, but the death of a
star or a supernova.
ROSAT Images of Tycho's SNR
4
BACKGROUND INFORMATION A light curve
reconstructed from Brahes observations has shown
that this supernova is a Type 1a. A star can
have different fates depending upon its mass. A
star with about the same mass as the Sun will
turn into a white dwarf. If this white dwarf is
in a binary system, it can accrete enough mass so
that it cannot support its own weight. The star
collapses and temperatures become high enough for
carbon fusion to occur. Fusion begins throughout
the white dwarf almost simultaneously and an
explosion occurs.
Type Ia Supernova
Tychos SNR
5
"To make an apple pie from scratch,you must
first invent the universe."
Carl Sagan
6
From
The elements have their ultimate origins in
cosmic events. Further, different elements come
from a variety of different events. So the
elements that make up life itself reflect a
variety of events that take place in the
Universe. The hydrogen found in water and
hydrocarbons was formed in the moments after the
Big Bang. Carbon, the basis for all terrestrial
life, was formed in small stars. Elements of
lower abundance in living organisms but essential
to our biology, such as calcium and iron, were
formed in large stars. Heavier elements
important to our environment, such as gold, were
formed in the explosive power of supernovae. And
light elements used in our technology were formed
via cosmic rays. The solar nebula, from which
our solar system was formed, was seeded with
these elements, and they were present at the
Earth's formation. Our very existence is
connected to these elements, and to their cosmic
origin.
7
The Periodic Table of the Elements
(coded according to the dominant processes which
produce the elements)
What elements are in Tychos SNR and how are they
distributed? What tools do scientists use to
answer these questions?
8
Chandra's look at Tycho's SNR
NASA's Chandra X-ray Observatory, which was
launched and deployed by the Space Shuttle
Columbia on July 23, 1999, is the most
sophisticated X-ray observatory built to date.
Incoming X-rays are focused by the mirrors to a
tiny spot (about half as wide as a human hair) on
the focal plane, about 30 feet away. The focal
plane science instruments, ACIS and HRC, are well
matched to capture the sharp images formed by the
mirrors and to provide information about the
incoming X-rays their number, position, energy
and time of arrival. Two additional science
instruments provide detailed information about
the X-ray energy, the LETG and HETG
spectrometers.
ds9 software (available as a free download from
the Chandra Ed website) allows educators,
students, amateur astronomers and the general
public to perform X-ray astronomy data analysis
using data sets from the Chandra X-ray
Observatory.
9
Your color-by-number image of a supernova
remnant from the activity Decoding Starlight?
ds9 makes images in a similar way. What can ds9
analysis tell you about the elements in Tychos
SNR? Lets find out!
Remember?
10
Tycho's Supernova Remnant
a ds9 activity
PURPOSE To use ds9 software to analyze the X-ray
spectrum of the Tycho Supernova Remnant,
determine the elements present, and investigate
the distribution of these elements in the remnant.
HYPOTHESIS Use prior knowledge about stellar
evolution to predict which elements you might
expect to see in a Type 1a supernova remnant and
how those elements might be distributed in the
remnant. Where would the heavier elements be?
Where would the light elements be? Explain your
reasoning. You may wish to read more first.
11
Sherpa Spectral Fit
PROCEDURE
12
What is Bremsstrahlung radiation?
A supernova remnant can have a temperature of
millions of degrees Kelvin. Bremsstrahlung
radiation occurs in such a hot gas where many
electrons are stripped from their nuclei, leaving
a population of electrons and positive ions. When
an electron passes close to a positive ion, the
strong electric forces cause its trajectory to
change. The acceleration of the electron in this
way causes it to radiate electromagnetic energy -
this radiation is called bremsstrahlung and
produces a continuous X-ray spectrum.
In addition, emission lines can appear
superimposed on this spectrum, corresponding to
the ejection of K and L shell electrons knocked
out of atoms by collisions with high-energy
electrons. Higher energy electrons then fall into
the vacated energy state in the outer shell, and
so on, emitting X-ray photons. The energies of
these emissions lines can be matched to energies
in the CHIANTI Atomic Database to identify the
elements in plasmas such as supernova remnants.
13
9. Enlarge the graph by dragging the lower right
corner. Either on the screen or on a printout of
the graph, measure the distance between O and 1
keV to the nearest tenth of a centimeter (mm).
This gives your scale in cm/keV. 10. Measure the
distance in cm (to the nearest 1/10 cm) from 0
keV to the center of each peak (X- ray emission
line). 11. Divide the distance to each peak (cm)
by your scale (cm/keV) to get the energy (keV) of
each emission line.
14
An alternative way of getting the energy of each
emission line is to create a zoom box by holding
the left mouse button down and dragging a box
around the line. When you click again, a zoom
will appear. Right clicking the mouse returns
you to the original graph.
15

• 12. Identify the elements for each X-ray emission
  line using the chart to the left. If you have
  lines whose energy is not close to that of one of
  the elements in the chart, leave that line
  unidentified.
• You may wish to use the CHIANTI database to get
  possible candidates for unidentified lines. You
  will need to convert energies in KeV to
  wavelengths in angstroms using E hc/l where h
  6.626X10-34 js, c 3 X 10-8 m/s,
  1 A 1.6 X10-10 m and 1 keV 1.6 X10-16 j.

element Energy (KeV)
0 0.18
Mg 0.25
Mg 0.27
C 0.31
C 0.37
O 0.64
O 0.66
Fe 0.80
Fe 0.81
Ne 0.92
Ne 0.93
Ni 0.95
Ni 0.98
Ne 1.02
Mg 1.33
Mg 1.45
Fe 1.66
Fe 1.67
Si 1.84
Si 1.87
element Energy (KeV)
Si 1.98
Si 2.13
S 2.42
S 2.44
S 2.60
S 2.88
S 2.95
Ar 3.10
Ar 3.32
Ar 3.69
Ca 3.86
Ca 3.89
Ca 4.11
Ca 4.95
Fe 6.47
Fe 6.54
Fe 6.97
Fe 7.80
Fe 8.26
16
Si 1.8 keV
Fe 0.8 keV
Mg 1.3 keV
S 2.4 keV
Ar 3.1 keV
Ca 3.9 keV
Fe 6.4 keV
17
Energy Distribution
0.1-10 keV Contour interval 750 counts
0.7-0.9 keV (in the region of Fe) Contour
interval 200 counts

• 14. Reload Obs id 115 (Tycho SNR) into ds9.
• 15. AnalysisgtDisplay Contours
• 16. If you wish to see the contour intervals
  AnalysisgtContours Parameters
• 17. Use Chandra Ed Analysis ToolsgtEnergy Cut to
  view the Tycho SNR in an energy band close to the
  energy values of each peak (choose a hi and lo of
  0.1 keV on either side of the line energy). This
  will help you see the distribution of the
  elements. AnalysisgtDisplay Contours is useful
  here.

18
Energy Distribution
0.1-10 keV Contour interval 750 counts
4-6 keV continuum Contour interval 19 counts
18. On your bremsstrahlung spectrum, there is an
energy continuum where there are no spectral
lines. Do an energy cut for this energy
interval. Think about what this area might
represent and why there are no spectral lines in
this region.
19
Energy Distribution
1.2-1.4 keV (Mg)
1.7-1.9 keV (Si)
0.1-10 keV
2.3-2.5 keV (S)
3.0-3.2 keV (Ar)
3.8-4.0 keV (Ca)
0.7-0.9 keV (Fe)
6.3-6.5 keV (Fe)
4-6 keV continuum
20
Si
Regional Spectra
Fe
Mg
S
Ar
Ca
19. Using various shaped regions, enclose areas
of interest from your energy cuts and create
bremsstrahlung spectra as you did for the whole
Tycho SNR.
21
Regional Spectra
Si
Fe
Mg
S
Ar
Ca
22
Regional Spectra
Si
Fe
Mg
S
Ar
Ca
23
Regional Spectra
Fe
Mg
Si
S
Ar
24
Regional Spectra
Si
Fe
Mg
S
Ar
25
Regional Spectra
20. Find a region that contains each of the
elements in the whole remnant as well as part of
the shockwave.
26
Tycho's Supernova Remnant

• CONCLUSIONS
• 1. Do the results of your ds9 analysis support
  your hypothesis? Why or why not?
• How do the spectra of different regions you
  investigated within the Tycho SNR compare to each
  other? What are their similarities and
  differences?
• Describe the shape of the region for the energy
  cut of the continuum that contained no spectral
  lines. What could this represent? Why doesnt
  it contain spectral lines?
• 4. Describe the features and shape of the Tycho
  SNR.

XMM-Newton, ESA
27

• FURTHER INVESTIGATIONS
• Conduct a similar investigation of other types of
  supernova. Go to AnalysisgtVirtual
  ObservatorygtChandra Ed Archive Server. At the
  bottom of the page that comes up, click
  Unofficial Chandra Public Archive. On this
  form, do a search by ObsID or the name of the
  supernova. Clicking on the title of choices that
  come up in the search will load the FITS image
  into ds9. You can view various supernovae in the
  Chandra Supernova Photo Gallery.

28
Two suggestions for further study would be Cas A,
a type II supernova remnant with a central
neutron star, and W49B, a prime candidate for
being the remnant of a gamma ray burst involving
a black hole collapsar. How do the types and
distributions of elements and the structures in
other types of supernova compare to that of
Tychos SNR?
Cas A
W49B

1. Research recent Hubble images that may have
   located the runaway binary companion to the white
   dwarf that exploded in Tychos supernova.
2. Investigate why Type 1a supernova can be used as
   standard candles (objects whose absolute
   magnitude is thought to be very well known and
   can, therefore, be used to find distances to
   galaxies that contain these objects).

Hubble Image Tychos companion?
29
Tycho's SNR Resources
a ds9 activity
X-Rays - Another Form of Light X-ray Sources
Supernovas Supernova Remnants Chandra's View
of Tycho's Supernova Remnant Chandra Education
Data Analysis Software Activities XMM-Newton
observation of the Tycho Supernova Remnant
(Astronomy Astrophysics) Chandra Observations
of Tycho's Supernova Remnant (Journal of
Astrophysics Astronomy The CHIANTI atomic
database Chandra Images by Category - Supernovas
Supernova Remnants Chandra Supernova Remnants
Catalog Universe Today - Survivor Found From
Tycho's Supernova Special thanks for assistance
with the development of this project to Dr.
Frederick Seward of the Smithsonian Astrophysics
Observatory.