NERSC helps expose cosmic transients

Every night the PTF camera – a 100-megapixel machine mounted on the 48-inch Samuel Oschin Telescope at Palomar Observatory in Southern California – will automatically snap pictures of the sky, then send those images to NERSC for archiving via a high-speed network provided by DOE's Energy Sciences Network (ESnet) and the National Science Foundation's (NSF's) High Performance Wireless Research and Education Network (HPWREN).

At NERSC, computers running machine-learning algorithms in the Real-time Transient Detection pipeline scour the PTF observations for "transient" sources, cosmic objects that change in brightness or position, by comparing the new observations with all of the data collected from previous nights. Once an interesting event is discovered, machines at NERSC will immediately, within minutes, send its coordinates to Palomar's 60-inch telescope and others for follow up observations.

"PTF is an example of the growing need to provide data services for science; it combines automated, real-time analysis with high-end systems and networks in a way that changes the way the scientific community works," says NERSC Director Kathy Yelick.

"We are currently uncovering one event every 12 minutes. This project will be keeping the astronomical community busy for quite a while," says Kulkarni.

"These tools are extremely valuable because they not only help us identify supernova, they uncover them while the star is in the act of exploding," says Robert Quimby of Caltech, who is the software lead for the PTF program. "This gives us valuable information about how cosmic dust is spread across the universe."

He notes that all chemical elements in the universe besides hydrogen and helium are created inside stars. When massive stars die in fiery supernova explosions, they blast these chemical creations out into space. The cosmic dust will eventually come together to form stars, planets, comets – even humans. Everything around us is made of stardust.

In addition to spreading stardust across the cosmos, some species of supernovae also play a vital role in helping us understand the nature of the universe. For example, because Type Ia supernova are relatively uniform in brightness, they act as cosmic lighthouses, helping astronomers judge distance. Many astronomers participating in the PTF survey are specifically searching for these cosmic creatures.

"It is very exciting to find so many supernovae, so early in the project. It's like we've just turned on the spigot and are now waiting for the fire hose to blast," says Quimby.

PTF is a collaboration of Berkeley Lab, Caltech, Columbia University, the NSF's HPWREN, the Infrared Processing and Analysis Center, Las Cumbres Observatory Global Telescope Network, Oxford University, University of California at Berkeley, and the Weizmann Institute of Science, Israel. PTF is partly supported by DOE's Scientific Discovery through Advanced Computing program; NERSC provided the storage and systems infrastructure. NERSC and ESnet are managed by the Berkeley Lab on behalf of the Office of Advanced Scientific Computing Research within the DOE Office of Science.