Early History of Supernovae S. R. Kulkarni Caltech Optical Observatories

Key Papers “On Supernovae” Baade & Zwicky (1934a) “Cosmic Rays From Supernovae” Baade & Zwicky (1934b) “On the Search for Supernovae” Zwicky (1938)

BAADE & ZWICKY (1934A)

Novae Facts known by 1934 Novae occur in our Galaxy at the rate of 30 per year Hubble studying novae in M31 (initially to determine distance to M31) and a similar rate is found Nova have typical brightness of -6 mag (with a range of 4 mag)

Other Facts known by 1934 Tycho Nova (AD 1572) was unusually bright But “pre-cursor” star for Tycho Nova was not bright S Andromeda (AD 1885) was very bright – Observed V=7.5 mag – Distance to Modulus to M31, DM=22.2 – [Modern Distance Modulus is 24.5] – Peak brightness [-17 modern]

Bright Novae (Baade & Zwicky) Bright novae are seen in distant nebula Many of them peak with a brightness similar to the “host” galaxy – M V = -15 Last about a month Observed Radiated light is erg – Two estimates for total energy release The rate is one per several centuries and conservatively one per thousand years (per galaxy)

Energetics: Baade & Zwicky (1934) Assume black body radiation from explosion to late times. Assume that we see a small fraction of energy in the optical – Two estimates: 1% to 100% of rest mass of the Sun Compute the black body radius at peak and divide by time to get velocity – Velocity = 60,000 km/s or v/c=0.2 – This v/c corresponds to 5% of proton rest mass

Baade & Zwicky (1934a) Super-novae thus represent transition of ordinary stars into a body much smaller in mass and are different from novae Supernovae are catastrophic

THE PALOMAR 18-INCH BEGINS SN SURVEY

Fritz Zwicky ( ) 5010

SN Spectroscopy Wide features seen in SN (a consequence of high ejection velocities) Zwicky begins his classification of SN (based on light curves)

P48 P inch 5015 P18

BAADE & ZWICKY (1934B)

Cosmic Rays 1912: Hess undertakes high latitude balloon flight and establishes that ionization radiation increases with altitude 1920: Millikan coins the term “Cosmic Rays” and argues for a photonic origin 1932: Chadwick discovers the neutron 1936: Hess wins Nobel Prize. Cosmic rays are now thought to be energetic charged particles (both positive and negative) AND OF UNKNOWN ORIGIN

Prior to Baade & Zwicky (1934) It was popular to speculate that cosmic rays came from intergalactic space B&Z note that cosmic ray energy density to galaxy-light is much larger than the ratio of cosmic rays to Galactic star-light. This, in their view, rules out an IGM or Early Universe explanation for cosmic rays and favors a Galactic origin for Cosmic Rays

B&Z, noting the large velocity of blast waves, suggest that cosmic rays arise in supernovae They compute the supernova energy injection rate and find that the resulting injection energy intensity to be comparable to the the intensity of cosmic rays CONCLUSION 1: Cosmic rays arise from supernovae

Conclusion 2:

4721 Palomar Observatory Museum

First Astronomical Use of Schmidt Camera The Schmidt design allows for wide field imaging with large aperture – The field of view of P48 is 47 square degrees! Wider field can be obtained by lenses (cf Rotse and others) Modern wide field imagers use very complex cameras which require very fine alignment (not easy, cf PS-1, LSST)

MOTIVATING TO THE PALOMAR TRANSIENT FACTORY

P48 Discovery P60 Confirmation 200-inch 5024

Homework for serious students Review the arguments presented in Baade & Zwicky (1934a) which led Baade & Zwicky to infer the explosion energy in supernovae to be between 1% and 100% of the rest mass of the Sun. Do you agree with the two analysis? What are the flaws? (or alternatively could there be SN with so much energy release).