X-ray spectroscopy of supernova remnants

Learning Objective:

To determine types of supernova events by examining Chandra X-Ray Observatory images of supernova remnants (SNR’s) and identifying the elements in their energy spectra.

Prerequisites: Read Chapter 17 of textbook.

Materials Required

Time Required: approximately 2-3 hours

Credit: NASA/CXC/Rutgers/J.Warren & J.Hughes et al

Tycho’s Supernova Remnant

In the year 1572, the Danish astronomer Tycho Brahe observed and studied the sudden appearance of a bright “new star” in the direction of the constellation Cassiopeia. Now known as Tycho’s supernova remnant, the event created a sensation in Tycho’s time because until then stars were thought to be unchanging. Tycho’s observations of this event marked the beginning of the study of astronomy as a science. This object is a Type Ia event.

SNR G292.0+1.8

The Type II core collapse of a massive star that produced this supernova remnant ~1600 years ago is located in the direction of the constellation Centaurus. SNR G292.0+1.8 is interesting because it is one of only three oxygen-rich remnants and one of the primary sources of the heavy elements necessary to form planets and people. Although considered a “textbook” case of a supernova remnant, the intricate structure shown here reveals a few surprises.

Tycho’s Supernova Remnant (Type Ia) and SNR G292.0+1.8 (Type II) are representative of the two supernova types. Follow the procedure below to analyze their spectra and determine the elements present in the remnants and their relative abundances.

Part I. Analysis of Data

Procedure

• Copy the below data tables to your lab report. Make sure that all data is typed.
• Examine Figure 1 from the downloaded and printed X-Ray Spectroscopy worksheet, the X-Ray spectrum of Tycho’s SNR. Six emission lines (peaks) have been identified for your measurements, Label these peaks 1 through 6.
• To get the energy of each emission line, measure the distance between 1 and 2 keV to the nearest tenth of a centimeter (cm). This gives a scale in cm/keV (the 1keV has been marked with a solid blue line for reference). Record this scale in your data table.
• Measure the distance in cm (with as much precision as possible) from 1 keV to the center of each peak (X- ray emission line). Make this distance negative if the peak is before 1 KeV and positive if it is after 1 keV. Record in the data table.
• Divide the distance to each peak (cm) by your scale (cm/keV) and add to 1 KeV to get the energy (keV) of each emission line. Record in the data table. (Show at minimum one full calculation of your answers. (Typed)

(d in cm)/(scale in cm/KeV) + 1 KeV

• Identify the elements for each X-ray emission line/peak using Table 1 Energies of X-ray Emissions Lines.  Match your number to the element that is closest in value to your number. Record answer in your data table.

Repeat steps #1-5 for Figure 2 from the downloaded and printed X-Ray Spectroscopy worksheet, the X-Ray spectrum of SNR G292.0+1.8.

Data:

Tycho’s SNR (Type Ia)

Scale: Distance from 1 KeV to 2 KeV      1 Kev = ________ cm

Data Table 1

# of

emission line

distance

from 1 KeV

(cm)

Energy of

emission line

(KeV)

chemical symbol

of element

——–

SNR G292.0+1.8 SNR (Type II)

Scale: Distance from 1 KeV to 2 KeV 1      Kev = ________ cm

Data Table 2

# of

emission line

distance

from 1 KeV

(cm)

Energy of

emission line

(KeV)

chemical symbol

of element

———

Table 1. Energies of X-ray Emission Lines

element

Energy (Kev)

element

Energy (Kev)

element

Energy (Kev)

O

0.18

Mg

1.33

Ar

3.32

Mg

0.25

Mg

1.45

Ca

3.69

Mg

0.27

Fe

1.66

Ca

3.86

O

0.64

Si

1.87

Ca

3.89

O

0.66

Si

1.98

Ca

4.11

Fe

0.80

Si

2.14

Fe

4.95

Fe

0.81

S

2.42

Fe

6.47

Ne

     0.92

S

2.44

Fe

6.54

Ne

0.93

S

2.63

Fe

6.87

Ne

1.02

Ar

3.10

Fe

7.80

Part II.  Conclusions and Data Analysis

1. What are the similarities and differences between these two spectra?
2. From the analysis of Tycho’s SNR and SNR G292.0+1.8, what elements are more predominant in a Type Ia supernova? Which are more predominant in a Type II? Are there elements present in one that are not in another?
3. Explain how you might be able to classify a supernova event as type Ia or type II from its spectrum based on your observations of Tycho’s SNR and SNR G292.0+1.8.

Part III. Additional Research

1. Research and explain, in a paragraph of 2-3 sentences, how and why a Type Ia Supernova occurs.
2. Research and explain, in a paragraph of 2-3 sentences, how and why a Type II Supernova occurs.
3. Summarize the major differences and similarities between these two types of  supernovas