Aussie Scientist Finds Rare Supernova at Keck Observatory

W. M. Keck Observatory press release by Dr. Duncan Forbes…

It was a dark and stormy night in the city of Angels. Well, actually it wasn’t. But more on that later…

It was a clear night on the summit of Mauna Kea at Keck Observatory on the 20th March. My colleagues and I were using the Echellette Spectrograph and Imager (ESI) instrument, which looks at faint objects in the visible wavelengths, to study star clusters and small galaxies.

Can you spot the supernova? Supernova SN2014ai on March 20th, 2014
I was actually in our special ‘remote ops’ room at Swinburne University, with my postdoc, Joachim Janz. This is a room decked out with a computer, a backup computer, a video-link to Keck Observatory and a dedicated Internet connection. As we are 21 hours ahead of Hawaii, it was a Friday afternoon when we started observing that Thursday night. My colleagues Sam Penny and Mark Norris were in the Keck control room, and Aaron Romanowsky was in his remote ops room at UC Santa Cruz.

Shortly into our night’s observing, we noticed a bright source in the guide camera image that wasn’t on our finding chart of that region. Still we managed to find our target and took a spectrum of it. But we decided to go back and see if that `new’ bright source was still there. Sure enough it was and it hadn’t moved. It was probably a supernova (or an asteroid coming straight at us!), so I decided to get a 5min spectrum with ESI. And indeed we had found a supernova—a type Ia to be exact. Type Ia supernovae are fairly rare in the nearby Universe and represent the explosion of at least one white dwarf star in a binary system. It is this same type of supernova that led to the discovery of Dark Energy in the Universe using the Keck Observatory, and three Nobel prizes.

Our supernova is located in the outskirts of a galaxy some 100 million light years from us—so it exploded 100 million years ago but the light only reached us that night.

I later found out that an automated telescope on the Palomar Mountain overlooking Los Angeles detected the supernova shortly before us. They also managed to get a spectrum but that was taken after our Keck II/ESI spectrum. The exciting thing is that both the Palomar Observatory and ourselves managed to observe the supernova in the 1-2 weeks before it reaches its maximum brightness (and then fades steadily after that).

The supernova has been given the designation SN2014ai.

All in all, not bad for a late night at the office…

Duncan Forbes is a professor of astronomy at Swinburne University in Melbourne, Australia, and a 2014 Evenings with Astronomers presenter at the signature Friends of Keck lecture series. Swinburne astronomers are awarded time for their research on Keck Observatory through an agreement with the California Institute of Technology.

Swinburne Team on Keck Discovers Farthest Supernova Ever

W. M Keck Observatory press release

Two ‘super-luminous’ supernovae — stellar explosions 10–100 times brighter than other supernova types — have been detected in the distant Universe, using the W.M. Keck Observatory on the top of Mauna Kea in Hawaii. The discovery, reported online in Nature this week, sets a record for the most distant supernova yet detected, and offers the rare possibility of observing the explosions of the first stars to form after the Big Bang.

Early Supernova
Simulation of a galaxy hosting a super-luminous supernova and its chaotic environment in the early Universe. Credit: Adrian Malec and Marie Martig (Swinburne University)
“The type of supernovae we’ve found are extremely rare,” said Jeff Cooke, astrophysicist at Swinburne University of Technology, whose team made the discovery. “In fact, only one has been discovered prior to our work. This particular type of supernova results from the death of a very massive star (about 100 – 250 times the mass of our Sun) and explodes in a completely different way compared to other supernovae. Discovering and studying these events provides us with observational examples to better understand them and the chemicals they eject into the Universe when they die.”

Super-luminous supernovae were discovered only a few years ago, and are rare in the nearby Universe. Their origins are not well understood, but a small subset of them is thought to occur when extremely massive stars undergo a nuclear explosion triggered by the conversion of photons into electron–positron pairs. Such events are expected to have occurred more frequently in the early Universe (at high redshift), when massive stars were more common. This, and the extreme brightness of these events, encouraged Cooke and colleagues to search for super-luminous supernovae at redshifts, z, greater than 2, when the Universe was less than one-quarter of its present age.

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Galaxies: some assembly required

Swinburne Observatory press release

New research using the world’s largest telescope at the Keck Observatory in Hawaii has revealed two distinct populations of star clusters surrounding galaxies that have radically different chemical compositions.

M22 or NGC6656 in Sagittarius, a classic globular cluster
An international team, led by Swinburne astronomers Christopher Usher and Professor Duncan Forbes, has measured the chemical composition of more than 900 star clusters in a dozen galaxies.

“This is ten times the number of star clusters previously examined, allowing us to confirm the existence of two chemically-distinct star clusters,” Mr Usher said.

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