* Astronomy

The Dawn of a New Era for Supernova 1987A

In February 1987, on a mountaintop in Chile, telescope operator Oscar Duhalde stood outside the observatory at Las Campanas and looked up at the clear night sky. There, in a hazy-looking patch of brightness in the sky - the Large Magellanic Cloud (LMC), a neighboring galaxy - was a bright star he hadn't noticed before.
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Title: Turning off the lights: Supernova SN1987A 30 years on
Author: Richard de Grijs

Decades-long repeat observations of supernova SN1987A offer us unique, real-time insights into the violent death of a massive star and its long-term environmental effects, until its eventual switch-off.

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Title: The Destruction of the Circumstellar Ring of SN 1987A
Author: Claes Fransson, Josefin Larsson, Katia Migotto, Dominic Pesce, Peter Challis, Roger A. Chevalier, Kevin France, Robert P. Kirshner, Bruno Leibundgut, Peter Lundqvist, Richard McCray, Jason Spyromilio, Francesco Taddia, Anders Jerkstrand, Seppo Mattila, Nathan Smith, Jesper Sollerman, J. Craig Wheeler, Arlin Crotts, Peter Garnavich, Kevin Heng, Stephen S. Lawrence, Nino Panagia, Chun S. J. Pun, George Sonneborn, Ben Sugerman

We present imaging and spectroscopic observations with HST and VLT of the ring of SN 1987A from 1994 to 2014. After an almost exponential increase of the shocked emission from the hotspots up to day ~8,000 (~2009), both this and the unshocked emission are now fading. From the radial positions of the hotspots we see an acceleration of these up to 500-1000 km/s, consistent with the highest spectroscopic shock velocities from the radiative shocks. In the most recent observations (2013 and 2014), we find several new hotspots outside the inner ring, excited by either X-rays from the shocks or by direct shock interaction. All of these observations indicate that the interaction with the supernova ejecta is now gradually dissolving the hotspots. We predict, based on the observed decay, that the inner ring will be destroyed by ~2025.

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Title: Dark Matter Balls Help Supernovae to Explode
Author: Colin D. Froggatt, Holger B. Nielsen

As a solution to the well-known problem that the shock wave potentially responsible for the explosion of a supernova actually tends to stall, we propose a new energy source arising from our model for dark matter. Our earlier model proposed that dark matter should consist of cm-large white dwarf-like objects kept together by a skin separating two different sorts of vacua. These dark matter balls or pearls will collect in the middle of any star throughout its lifetime. At some stage during the development of a supernova the balls will begin to take in neutrons and then other surrounding material. By passing into a ball nucleons fall through a potential of order 10 MeV, causing a severe production of heat - of order 10 foe for a solar mass of material eaten by the balls. The temperature in the iron core will thereby be raised, splitting up the iron into smaller nuclei. This provides a mechanism for reviving the shock wave when it arrives and making the supernova explosion really occur. The onset of the heating due to the dark matter balls would at first stop the collapse of the supernova progenitor. This opens up the possibility of there being {\em two} collapses giving two neutrino outbursts, as apparently seen in the supernova SN1987A - one in Mont Blanc, and one 4 hours 43 minutes later in both IMB and Kamiokande.

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