Supernovae are intensely bright objects. They are formed when a star reaches the end of its life with a dramatic explosion, expelling（驱逐，排出） most of its material out into space. The subject of this new Hubble image, spiral galaxy¹ NGC 6984, played host to one of these explosions back in 2012, known as SN 2012im. Now, another star has exploded, forming supernova SN 2013ek -- visible in this image as the prominent（突出的）, star-like bright object just slightly above and to the right of the galaxy's center.

 

SN 2012im is known as a Type Ic supernova, while the more recent SN 2013ek is a Type Ib. Both of these types are caused by the core collapse² of massive stars that have shed -- or lost -- their outer layers of hydrogen. Type Ic supernovae are thought to have lost more of their outer envelope than Type Ib, including a layer of helium.

 

The observations that make up this new image were taken on August 19, 2013, and aimed to pinpoint³ the location of this new explosion more precisely⁴. It is so close to where SN 2012im was spotted⁵ that the two events are thought to be linked; the chance of two completely independent supernovae so close together and of the same class exploding within one year of one another is a very unlikely event. It was initially⁶ suggested that SN 2013ek may in fact be SN 2012im flaring⁷ up again, but further observations support the idea that they are separate supernovae -- although they may be closely related in some as-yet-unknown way.

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