Serendipitous Supernova

By Steve Jefferson

Two weeks ago a group of astronomy students from the University of London Observatory were getting an introductory demonstration on how to use a telescope-mounted camera. With clouds shrouding much of the sky, professor Steve Fossey decided to point the University’s 14-inch telescope at nearby galaxy Messier 82 (M82) and saw a very bright object that wasn’t supposed to be there. After a bit of detective work, the group put out an Astronomical Telegram to the world’s scientific community. 

It was soon determined that M82 was hosting a rare, Type 1a supernova explosion – one of the brightest events in the sky and a once-in-a-century event. It was named SN2014J. 

The phones rang at Keck Observatory, home of the two largest and most scientifically productive telescopes on the Earth. Although time on the Keck telescopes is scheduled 6 months in advance and is highly coveted, the two different teams observing on Keck I and Keck II that night both agreed to interrupt their research and point the mighty 10-meter telescopes at M82 and gather valuable data and rare insight into the life cycle of type 1a supernova.

“It was very exciting: this was the second nearest supernova in recent history,” said Michael Liu, the University of Hawaii astronomer who made the decision to observe the exploding star using the Keck II telescope. “Usually, we know what we are going to be observing for months before we get here.”

While it’s known that Type 1a supernovae form from collapsing white dwarfs – the densest forms of matter after black holes and neutron stars – their formation theories come in two flavors: the single degenerate scenario in which a normal star is consumed by a white dwarf; and the double degenerate scenario in which two white dwarfs merge.

To determine which one this is, scientists need to compare the before and after images to determine which stars became the supernova, said Shriharsh Tendulkar, a post-doctoral researcher at the California Institute of Technology.

“Keck‘s Adaptive Optics system allows you to get very sharp images of the sky, as you would from space, and allows a very precise position of the supernova,” he said. “We can compare it to old images to possibly determine the progenitor system.” 

With the NIRC2 instrument and Keck II’s Adaptive Optics system (AO), Liu’s team was able to capture very clear images of the supernova and the surrounding stars in Messier 82.

“While there are many supernovae explosions in the Universe, this one is important because it is close enough that with Keck’s AO, we have an excellent chance of identifying the progenitor,” said Bob Goodrich, head of night-time operations for W. M. Keck Observatory

Critically, the supernova was discovered two weeks before its predicted peak luminosity, allowing an unprecedented opportunity to study the process of this stellar explosion.

“The physics of supernovae is very interesting,” Shriharsh said. “For example, it’s really hard to model these explosions in [computer] simulations. These observations will help us make our simulations better.”

Yale University astronomer Meg Urry also took time from her program on Keck I to gather data on M82 using the Observatory’s newest instrument, MOSFIRE, the Multi-Object Spectrograph for Infrared Exploration. She wrote about her perspective in an interesting article for CNN.

“In addition to giving insight on how these supernovae are formed, gathering data on SN2014J will give us more accurate distances to other type 1a supernovae,” Goodrich said. “Because the distance of M82 is precisely known, we can clearly determine the absolute brightness of SN2014J. Since all type 1a supernovae are equally bright, this valuable measurement can be used to calibrate data on all former (and future) such studies, including the one that lead to the Nobel Prize.”

Type 1a supernovae have already played a profound role at the Keck Observatory when a team of astronomers were awarded the 2011 Nobel Prize in Physics. The scientists trained the mighty Keck telescopes at known supernovae and used their findings to determine that the expansion of the Universe was not slowing down, as was expected, but in fact was speeding up – driven by a mysterious repelling force now called Dark Energy.