# Presentation: 601319

## SPACE FORENSICS:Death of a Star

- Sara Mitchell
- Jim Lochner
- NASA Goddard Space Flight Center
- Greenbelt, Maryland

## Slide 2

**Notes:**
Imagine you look up at the night sky and see the same thing every evening.  

But one night... [click]

Something has changed!  What is it?  What could it be?

Someone might suggest that it’s a “supernova.”  But what’s that?

## What’s a supernova?

## Can you spot the supernova?

## Supernova Timeline

- Earliest recorded supernova — 185 A.D. in China
- Famous historic supernovae in 1006, 1572, and 1604 A.D.
- First telescope built in 1608 by Hans Lippershey
- Multiwavelength observations of supernova remnants began in 1937

## Beginning the Investigation

- What do we want to **know **?

**Notes:**
Here is an opportunity to solicit questions that your audience would want to know if they looked up and spotted a supernova.  Like...
- Why did it happen?
- How long ago did it happen?
- Could we have predicted it?  Were there any signs?
- What's left over?
 What kind of star was this?
 How far away is it?
 Will it affect us?

Write down these questions and address them during the following slides and activities.

## Case File: Cassiopeia A

- Host Galaxy: Milky Way
- Constellation:  Cassiopeia
- Galactic Coordinates: G111.7-2.1
- Distance: ~10,000 light years
- Discovery: 1947
- Interesting facts:
- Discovered by radio observation
- Strongest radio source in the sky beyond our solar system

- Image: Chandra X-Ray Observatory
-            August 19, 1999

**Notes:**
Our “corpse” for this presentation is the supernova remnant Cassiopeia A, and this slide covers the background of the object.  There are many great websites with information about Cas A, as it is often called.

## Crime Scene Photographs

- Visible

- X-Ray

- Radio

- Infrared

- Hot gas
- (50 million degrees)

- Clumps of matter
- (10,000 degrees)

- Dust grains
- (several hundred degrees)

- Spiraling high energy electrons

**Notes:**
This slide explores how and why scientists study the same objects using different wavelengths of light.  As you click through the text, you can see what each wavelength reveals.  Invite the audience to compare and contrast each image, and perhaps to discuss false color -- these images have been processed to highlight features of the object.

After this discussion, reflect on this evidence and the original questions you have listed -- have we answered any questions?  Have we come up with any new ones?

## Why Multiwavelength?

**Notes:**
This slide continues the exploration of multiwavelength astronomy.

Imagine if you could see only a tiny sliver of a baseball field. You would never be able to figure out the rules of the game. In the same way, we need x-ray, gamma-ray, ultraviolet, infrared and radio telescopes to cover the full range of wavelengths to get an accurate picture of what is happening in the universe. 
(click once for blacked-out version)
(click again for full playing field)

## Supernova “DNA”

## “Signature” Spectroscopy

**Notes:**
This activity extends the discussion of spectroscopy and how scientists can use it to determine the location of the specific chemical elements in the supernova.  

Prepare by taking and printing photographs of your class or small groups of students.  If that is not feasible, print out images of recognizable groups of people (movie or TV casts, musical bands, etc.).  

Provide each group with an image along with an overhead transparency and permanent markers.  Instruct audience to line up the image (bottom) and transparency (top), and mark the location of each person in the image by writing their names over their faces on the transparency.  

Have each group swap only their transparency with another group.  Can they figure out what was in each image, just from the names on the transparency?  What information could they figure out from these transparencies?  

This activity mimics the satellite images shown on the following slide.  

## Looking for Signatures

- All X-Ray
- Energies

- Calcium

- Silicon

- Iron

**Notes:**
These images are designed to show the distribution of some of the elements ejected in the explosion that produced Cas A. The elements are part of a gas that has a temperature of about 50 million degrees Celsius. The colors represent intensity of X rays, with yellow the most intense, then red, purple, and green.  Compare and contract each image.  What do they tell us?

The broadband image, which shows all the X rays detected from Cas A, is more symmetric than the others. 
The silicon image shows a bright, broad jet breaking out of the upper left side of the remnant, and faint streamers in an opposite direction. This jet could be due to an asymmetry in the explosion, or loss of mass by the star before it exploded.
The calcium image is similar to the silicon image, but less bright and clumpier. 
The iron image shows significant differences from other images. Since iron is the heaviest element shown, these maps support the suggestion that the layers of the star were overturned either before or during the explosion.   The lack of iron in the jet limits the amount of energy that could have been in the jet.
Astronomers use these images to guide further investigations.
Reflect on this activity and the original questions posed by your audience.  

## Case Closed?

- Have we answered all of our questions?
- Have we found new questions?
- Where else can we find answers?
- What could we learn from seeing a “live” supernova?

**Notes:**
This slide serves as a reflection point as we move on to the final section of the presentation.  Look over the questions written down at the beginning of the presentation and consider these points.

## Is Cas A a “cold case”?

- Image: SN2005cs
- © 2005-2007 by R. Jay GaBany
- http://www.cosmotography.com

**Notes:**
Astronomers didn’t get to see Cassiopeia A until years after it exploded -- but sometimes we have the opportunity to see a “live” supernova.  What could we learn from this experience?

This pair of images, used earlier in the presentation, are a before-and-after of a supernova that occurred in 2005.  

## Is Cas A a “cold case”?

- Image: SN2005apSloan Digital Sky Survey

**Notes:**
This pair of images is another before-and-after of a recent supernova, observed in 2005 by the Sloan Digital Sky Survey.  What could we learn from this?

Reflect briefly on the opportunities afforded by seeing a supernova as it happens, instead of viewing a supernova remnant from a past explosion.

## Larger Body of Evidence 

- Crab Nebula
- (from SN 1054)

- Tycho’s SN
- (SN 1572)

- Kepler’s SN
- (SN 1604)

- SN 1987A

**Notes:**
One other possible body of evidence in exploring supernovae are other supernova remnants -- these images, taken by Chandra, are of four other famous supernova remnants.  Compare the images of Cas A to these.  How are they similar?  How are they different?  Do these images suggest that a supernova remnant changes over time?

Where would Cas A fit in this slide?

## Space Forensics: The Big Picture