The Cosmic Distance Ladder IV

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The Cosmic Distance Ladder IV
Dr. Frederic V. Hessman Universitäts-Sternwarte
Göttingen
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IV Distances to Supernovae
Supernovae
Supernovae (Thursday)
External Galaxies
Our Galaxy
Solar System
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Supernovae
SN II
SN Ia
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Supernovae

• Explosions (1051 ergs)
• Different types
• - old stars
• Typ Ia (O,Mg,Si,S,Ca,Fe,Co)
• Typ Ib (O,Ca,Fe,Mg)
• Typ Ic (He,Fe,Ca,O,Mg)
• - new, massive stars
• Typ II (e.g. SN1987a) (H!,..)
• Standard Candles for distance measurements
• (Typ Ia)

Typ I
Typ II
MPI für Astrophysik, Garching
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What does one see when a Supernova explodes?
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Distances to Type Ia Supernovae

• Always same luminosity/brightness at maximum
• Observe light curve ?Luminosity (Watt)

• Flux (in Watt/m²)
• Calibration with Standard Stars again
• Flux(Supernova) ?i Image(Supernova)
• Flux(Stnd) ?i Image(Stnd)

• Distance d from
• Flux Luminosity / 4?d²

Area 4?d²
d
Area 1 m²
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Image Processing with Hands-On Universe
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Possible Image Operations
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Steps to Discovering a Supernova

• Subtract the sky (Find mean background)
• Determine the reference frame (Position
  of reference star)
• (Rotation) (often not needed)
• Translation (in X and Y)
• Normalization (e.g. different transparency,
  clouds, exposure times)
• Subtraction

Background Star
Image A
Image B
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Result
etc. for all the images in our series!