Supernova hunters discover a rare beast

The work of the Galaxy Zoo : Supernova hunters recently paid off with the publication of a paper about a rather unusual supernova. Lead author, Kate Maguire – an astronomer at the University of Oxford working on supernovae and in particular exploding stars that can be used to measure the expansion of the Universe – tells us more :

The supernova named ‘PTF10ops’ was discovered by the supernova zoo using images from the Palomar Transient Factory Telescope in California and a report on this interesting SN has now been accepted for publication in the journal, Monthly Notices of the Royal Astronomical Society. Thanks to the very rapid discovery of this supernova by members of the supernova zoo, we were able to start taking observations very soon after explosion with many telescopes around the world such as the 4.2 m William Herschel Telescope on the Canary Island of La Palma, the 3 m Shane telescope at the Lick Observatory, California and at one of the two 10 m telescopes located at the Keck Observatory in Hawai’i.

An image of the field of PTF10ops (located at the centre of the crosshairs) taken with the WHT+ACAM on La Palma, Canary Islands. The largest galaxy with spiral arms located in the upper left quadrant is the host galaxy of PTF10ops, located at a distance of 148 kpc from the supernova position. This is the largest separation of any SN Ia discovered to date.

PTF10ops turned out to be a very interesting supernova – a peculiar type Ia supernova. Type Ia supernovae are explosions that occur when a white dwarf (a small, dense star) collapses when it pulls matter from a companion star and grows to have a mass of more than 1.4 times that of the Sun. At this critical mass, a thermonuclear reaction is triggered, that destroys the star in a massive explosion that we call a type Ia supernova. Type Ia supernovae are very important because they are used as cosmological distance indicators and were used in the discovery that the expansion rate of the universe is accelerating.

PTF10ops had unusual observational properties that suggest that maybe a new type of supernova explosion has been discovered. It is located very far from its host galaxy, actually the farthest supernova from the centre of its host galaxy discovered to date. Its spectra also contained signs of rare elements such as Titanium and Chromium. In normal Type Ia supernovae, how long a supernova stays bright is directly related to its peak brightness, but PTF10ops did not follow this rule and stayed brighter for much longer than expected. It is still unclear what it was about the star that exploded that produced this unusual supernova, maybe it was very old star or maybe we are seeing some sort of new, unknown explosion.

In the future, we hope to take images of more objects like this using the Palomar Transient Factory and then with the invaluable help of the supernova zoo members, we can catch these supernovae very soon after explosion and start follow up observations immediately to get images and spectra to better understand these rare supernova explosions.

P.S. Here’s the piece of the paper crediting the discoverers – well done all!