The most-luminous supernova ever observed has been discovered by a team of astronomers, including Carnegie’s Benjamin Shappee, Nidia Morrell, and Ian Thompson, called ASAS-SN-15lh.
A supernova is a rare astronomical event that occurs during the last stellar evolutionary stages of a massive star’s life, whose dramatic, violent, and catastrophic destruction is marked by one final titanic explosion. For a short time, this causes the sudden appearance of a “new” bright star in the heavens, before slowly fading from sight over several weeks or months.
Only three Milky Way naked-eye supernova events have been observed during the last thousand years, though many have been telescopically seen in other galaxies.
The unusual quality about this recent spotting is that it’s two-times more luminous than any previously discovered. In fact, ASAS-SN-15lh at peak was almost 50 times more than the entire Milky Way galaxy!
“When the first du Pont spectrum was available, as usual, I quickly checked what kind of supernova it was,” Morrell said. “To my surprise, I was not able to even tell for sure it was a supernova. My first reaction was: ‘this is interesting, we should get more data.’ It was only when we obtained higher resolution spectra from the Southern African Large Telescope and the Magellan Clay Telescope that I realized how distant the host galaxy is and consequently, how luminous the supernova.”
What’s more, they determined that the galaxy where ASAS-SN-15lh formed is very atypical for a super-luminous supernova, which raises questions about how these types of supernovae form.
Image: Comparison between a false-color pre-explosion image from the Dark Energy Survey and false-color follow-up image of from the LCOGT 1-m network, courtesy of Benjamin Shappee.