Eta Carinae and pair instability supernovae

The progenitors of pair instability supernovae are thought to be the most massive stars, and may have been more common in the early Universe. An Australian team, using Keck, has recently searched for such events at high redshift and discovered the most distant example, at z = 3.9. From A. Gal-Yam et al., a paper concerning SN2007bi published in Nature in 2009:

Stars with initial masses between ten and one hundred solar masses fuse progressively heavier elements in their centres, up to inert iron. The core then gravitationally collapses to a neutron star or a black hole, leading to an explosion — an iron-core-collapse supernova (SN). In contrast, extremely massive stars with initial masses greater than 140 solar masses, if such exist, have oxygen cores which exceed fifty solar masses. There, high temperatures are reached at relatively low densities. Conversion of energetic, pressure-supporting photons into electron-positron pairs occurs prior to oxygen ignition, and leads to a violent contraction that triggers a catastrophic nuclear explosion. Tremendous energies (>1052 erg) are released, completely unbinding the star in a pair-instability SN (PISN), with no compact remnant.

Eta Carinae, around 2.5 kpc distant, was famously observed to erupt in the mid-nineteenth century to outshine Canopus in the southern sky. The occurrence gave rise to the remarkable bipolar nebula imaged above. The star itself is a luminous blue variable with 100 – 120 solar masses, and might also become a pair instability supernova, leaving behind no black hole but a huge abundance of heavy elements, possibly within a 104 year timescale. If the eta Carinae event were comparable to the most instrinsically luminous supernova yet observed, SN2006gy, its apparent magnitude would exceed -10.

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2 Responses to “Eta Carinae and pair instability supernovae”

  1. […] have posted previously about eta Carinae and the likelihood it may go supernova very soon. Suffice to say it is one of the most massive […]

  2. […] in distant galaxies which appear unexpectedly luminous. The first gives an alternative to the pair instability route for the most massive stars, postulating supernovae driven in part at least by draining energy […]

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