Serendipitous Supernova

An image of the area of M82 acquired from the Keck Observatory using the NIRC2 instrument and the Keck II Adaptive Optics (AO) system showing the supernova SN2014J. By accurately matching the NIRC2 image to an archival HST image, astronomers can infer properties of the progenitor star or progenitor system that led to the supernova, confirming or discarding different hypotheses. Keck Observatory's AO systems allow astronomers to reduce the blurring effect of atmospheric turbulence and acquire images as sharp as observed from space. Credit: Caltech/UH

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. 

By Steve Jefferson

Source: W. M. Keck Observatory

First Light of Powerful New MOSFIRE Instrument

An unprocessed image of M57, the Ring Nebula in the constellation Lyra, from April 5, 2012. Credit: W. M. Keck Observatory

April 5, 2012, infrared spectra from NGC5053, a globular cluster in the constellation Coma Berenices. Credit: W. M. Keck Observatory

Unprocessed April 5, 2012, infrared image of M82, an exotic galaxy in Ursa Major. Credit: W. M. Keck Observatory

Kamuela, HI – Engineers and astronomers are celebrating the much anticipated first light of the MOSFIRE instrument, now installed on the Keck I telescope at W. M. Keck Observatory. MOSFIRE (Multi-Object Spectrometer For Infra-Red Exploration) will vastly increase the data gathering power of what is already the world’s most productive ground-based observatory.

“This is a near-infrared multi-object spectrograph, similar to our popular LRIS and DEIMOS instruments, only at longer wavelengths,” explained Keck Observatory Observing Support Manager Bob Goodrich. “The MOSFIRE project team members at Keck Observatory, Caltech, UCLA, and UC Santa Cruz are to be congratulated, as are the observatory operations staff who worked hard to get MOSFIRE integrated into the Keck I telescope and infrastructure. A lot of people have put in long hours getting ready for this momentous First Light.”

The first images from MOSFIRE were made on the night of April 4, despite thick cirrus clouds over Mauna Kea. One subject was a pair of interacting galaxies known as The Antennae. Additional images and spectra were gathered on the night of April 5, as part of the continuing commissioning of the instrument.

MOSFIRE gathers spectra, which contain chemical signatures in the light of everything from stars to galaxies, at near-infrared wavelengths (that is, 0.97-2.45 microns, or millionths of a meter). Infrared is light which is beyond red in a rainbow—just beyond what human eyes can detect. Observing in the infrared allows researchers to penetrate cosmic dust clouds and see objects that are otherwise invisible, like the stars circling the supermassive black hole at the center of the Milky Way. It also allows for the study of the most distant objects, the light of which has been stretched beyond the red end of the spectrum by the expansion of the universe.

Astronomers plan to use MOSFIRE to study the time when most galaxies formed, as well as the so-called period of re-ionization, when the universe was just a half-billion to a billion years old. Other targets will be nearby stars, young stars and even brown dwarfs, which are stars not quite massive enough for normal nuclear fusion to ignite in their cores.

What sets MOSFIRE apart from other instruments is its vastly more light-sensitive camera and its ability to survey up to 46 objects at a time, then switch targets in just minutes. That’s an operation that takes comparable infrared instruments one to two days.

MOSFIRE can also scan the sky with a 6.1 arc minute field of view, which is about 20 percent of a full moon and almost a hundred times more sky than the Keck’s current near-infrared camera. To take spectra of multiple objects, the state-of-the-art spectrometer consists of 46 pairs of sliding bars that open and close like curtains. Aligned in rows, each pair of bars blocks the sky, leaving small slits between the bars which allow slivers of light from multiple stars or galaxies to be recorded. Light from each slit then enters the spectrometer, which breaks down the objects’ light into their spectrum of wavelengths.

Because everything that’s even a little warm radiates infrared light, all infrared instruments must be kept cold to minimize any trace of heat from the ground, the telescope, or the instrument itself from contaminating the infrared signals from space, MOSFIRE is kept at a cool 120 Kelvins (about -243 degrees Fahrenheit or -153 degrees Celsius). Because of this, MOSFIRE is the largest cryogenic instrument on either of the Keck telescopes.

“We look forward to the rest of MOSFIRE commissioning, and the start of science operations,” said Goodrich.

UCLA’s Ian McLean, Caltech’s Chuck Steidel and Caltech’s Keith Matthews, who have built other Keck instruments, played leading roles. The team includes Keck Observatory’s Sean Atkins, the engineering and technical staff of Keck Observatory, the technical staff of the UCLA Infrared Lab, master optical designer Harland Epps of UC Santa Cruz and the staff of Caltech Optical Observatories. The spectrometer was made possible through funding provided by the National Science Foundation and a generous donation from astronomy benefactors Gordon and Betty Moore.

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The W. M. Keck Observatory operates two 10-meter optical/infrared telescopes on the summit of Mauna Kea on the Big Island of Hawaii. The twin telescopes feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectroscopy and a world-leading laser guide star adaptive optics system which cancels out much of the interference caused by Earth’s turbulent atmosphere. The Observatory is a private 501(c) 3 non-profit organization and a scientific partnership of the California Institute of Technology, the University of California and NASA.