New class of supernova intrigues astronomers

The Palomar Transient Factory (PTF) at Caltech has discovered a new class of bright supernovae that has astronomers baffled. The properties of these objects — extreme brightness, high ultraviolet luminosity, the presence of oxygen and lack of metals common to most supernovae — are not explained by current theoretical models. PTF astronomers speculate that these objects could be the result of exploding supermassive stars with 100 times the mass of the Sun or perhaps even magnetars (rapidly rotating neutron stars with super-strong magnetic fields).

The PTF uses an automated system that includes a telescope that scans large portions of the sky night after night using a wide-field imaging camera, and an algorithm that looks for transients — anything that has varied in brightness and/or position — by comparing these images with images from previous nights. When a transient is discovered, its coordinates are automatically sent to a larger telescope at Palomar for further observation. Finally, if the transient turns out to be interesting enough, an actual astronomer will follow-up with even more observations on an even bigger telescope.

This turns out to be an excellent way to pore over the sky looking for supernovae, which are exceedingly short-lived as cosmic events go — a typical supernova will begin to fade after just a few weeks. Prior to automated sky searches like PTF, this meant that catching a supernova in the act was to a large degree a matter of luck. Even though they’re extremely luminous events, most supernovae occur in galaxies that are so far away that they appear as faint dots in astronomical images. Yet there’s a universe potentially brimming over with them. Astronomers estimate that one in every 100 Milky Way-like galaxies will experience a supernova event each year. With about a hundred billion galaxies in the observable universe — about 20% of which are spirals like the Milky Way — that’s potentially hundreds of millions of events every year, and obviously astronomers want to catch as many of them as they can.

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