Supernova factory

Commissioning of the Palomar Transient Factory, which combines imaging with rapid data analysis and follow-up by other telescopes, is to be completed this month. “We will search for objects which change on the time scale of minutes, hours, and days,” says PTF principal investigator Shrinivas Kulkarni of Caltech. The PTF has already discovered more than 40 super-novae since first light last December.

Located at Caltech’s Palomar Observatory in Southern California, the PTF’s wide-field-of-view camera, which is mounted on a 1.2-m optical telescope, piles up more than 100 gigabytes of data each night. As they’re collected, those data are sent by a high-speed microwave connection to Lawrence Berkeley National Laboratory, where they are immediately compared with previous images.

“The 1.2-meter is a discovery engine. It finds approximately one transient object every 17 minutes,” Kulkarni says. Data on transients found in the computerized analysis are returned to Palomar, where a 1.5-m telescope that is dedicated halftime to the project “provides vital filtering” down to a few objects a night for further observation. Telescopes around the globe to which the PTF’s eight institutional partners in the US, UK, and Israel have access are notified about the selected objects. Although the PTF is mostly robotic, human eyes still double-check that the selected objects warrant more study. Software under development could reduce the notification time from 24 hours to real time, Kulkarni adds.

The tab for construction plus five years of running the PTF is about $2.6 million. “The cost has been kept low by the participation of many young people who were given major responsibility,” Kulkarni says, noting that his postdoc Nick Law is the PTF project scientist.