A Caltech-led project that includes University of Maryland astronomers has been selected to receive $4.5 million over five years by the National Science Foundation through its Partnership for International Research and Education (PIRE) program. The project aims to improve our understanding of cosmic transients--ephemeral, extremely bright flashes of light that suddenly appear in the night sky, shining like new stars--a million to a billion times brighter than the sun--then quickly fading away.
The project, dubbed Global Relay of Observatories Watching Transients Happen (GROWTH), is a collaboration between six universities in the United States and six abroad. It formally establishes a network of telescopes at longitudes throughout North America, Asia and Europe to extend the hours of night-time observing, enabling researchers to continue monitoring cosmic transients that might otherwise disappear before the next night in a single location.
At UMD, undergraduates in two new courses will analyze data collected by the telescopes to obtain scientifically useful results. The courses--one for astronomy majors and one for non-astronomy majors--will use "flipped" learning environments and active-learning techniques, with students working together in small groups and participating in an online forum to discuss their research results with students and faculty members who are analyzing GROWTH data at several other institutions and have the same challenges and goals.
"Our students will get to analyze real data generated by several state-of-the-art facilities on objects such as exoplanets, asteroids, variable stars, novae and supernovae," says Stuart Vogel, chair of the UMD Department of Astronomy. "I am very excited that so many undergraduate students at Maryland will get the opportunity to participate in real research through the GROWTH project."
The new courses will be modeled after a highly successful course for non-astronomy majors at UMD called "Astronomy in Practice," which was developed and taught by Melissa Hayes-Gehrke, a senior lecturer in astronomy at UMD. In that course, students observe asteroids with Internet-controlled telescopes and analyze the asteroids' rotational patterns. In 2013, students in the course made a rare discovery that wowed professional astronomers: a previously unstudied asteroid is actually a pair of asteroids that orbit and regularly eclipse one another.
"The success of the Astronomy in Practice students, who have published eight papers over two semesters, demonstrates that non-astronomy majors are able to conduct real scientific research," says Hayes-Gehrke. "The new courses being developed for both astronomy majors and non-astronomy majors will enable students from across campus to analyze and make discoveries with new data from the GROWTH project."
Many GROWTH observations will begin with a transient candidate discovered in the data stream generated every night by the Palomar Transient Factory (PTF), a fully automated, wide-field survey systematically searching for such flashes using a camera mounted on the 48-inch Samuel Oschin Telescope at Palomar Observatory in California. (A new version of that survey, called the Zwicky Transient Facility (ZTF), will be an order of magnitude more sensitive and will play a crucial role in making those initial discoveries when it comes online in 2017.) If a candidate looks promising, follow-up observations will be triggered with the Gemini North telescope or the W. M. Keck Observatory, both in Hawaii, gaining three additional hours of darkness. After collecting data there, the team might contact members of the network in Japan or Taiwan, then India, Israel, Sweden and Germany.
"By probing wider and faster, the ZTF will open up a new region of discovery space for transients, and the GROWTH network will make it possible to study these ephemeral events as they evolve in real time," says Suvi Gezari, an assistant professor in astronomy at UMD.
While supernovae--explosions related to the collapse of massive stars--typically fade over months, some cosmic transients, especially rarer events such as the merger of two extremely dense stellar remnants called neutron stars, or the merger of a neutron star and a black hole, are believed to disappear in a matter of hours--a day at most. Some of these more exotic transients are thought to be the source of heavy elements, such as gold and platinum. But no one has seen, in action, the process that creates them.
"None of the explosions that we've found so far has been extreme enough to actually synthesize enough heavy elements," says GROWTH project leader Mansi M. Kasliwal, an assistant professor of astronomy at Caltech. "As you try to find these rarer and rarer events, you need to be able to respond quickly because the flash of light they produce is even more short-lived, and that's where GROWTH becomes necessary."
Even being able to observe supernovae within a few hours of the blast yields important information that is lost if observations are completed later. That is because after the initial burst flash-ionizes everything, a shock wave follows, sweeping up all the surrounding material. And with that material goes a lot of data about the progenitor, the star that exploded.
"If you respond quickly enough to a young supernova, you can get direct clues about the progenitor system," explains Kasliwal. "With our network, the most common events that we will follow up are very young supernovae that are within a few hours of explosion. For the first time, we're seeing certain ionization lines, which tell us what sort of star it was that just died and gave rise to this particular supernova."
Beyond rapid response, the GROWTH network is also able to use ground- and space-based telescopes to observe cosmic transients at X-ray, ultraviolet, infrared, optical, and radio wavelengths. In addition, the GROWTH network will also help detect and characterize small near-Earth asteroids--those with a diameter smaller than about 140 meters, which can still do significant damage.
This is the fifth round of PIRE funding since the program started in 2005 with the goal of supporting innovative, high-quality projects in which advances in research and education could not occur without international collaboration. The award provides the resources for students and postdocs to interact closely with international partners through extended visits and internships.
Working with UMD's GRAD-MAP (Graduate Resources Advancing Diversity with Maryland Astronomy and Physics) program, students from minority-serving institutions located mostly in the Washington, D.C. metro area will participate in GROWTH summer internships.
"Undergraduate research experience is essential for future success in STEM careers, and students who participate in the GROWTH project will gain this essential experience while working on diverse, interdisciplinary teams," says GRAD-MAP leader Ashlee Wilkins, a UMD astronomy graduate student. "GROWTH's student interns will be ready to apply analytical and communications skills to projects such as the Large Synoptic Survey Telescope and the Laser Interferometer Gravitational-Wave Observatory, as well as in STEM fields far beyond time-domain astronomy."
UMD's participation in the PTF and ZTF is through the Joint Space-Science Institute (JSI), a collaboration between UMD's Departments of Astronomy and Physics and NASA's Goddard Space Flight Center.
"I'm most excited for the possibility of really new discoveries, things we hadn't even imagined before. Because we will never be stopped by sunrise, GROWTH will open a new window into short timescale variability. The universe is such a wild and dynamic place - who knows what we find?" says Brad Cenko, a research astrophysicist at NASA's Goddard Space Flight Center and adjunct assistant professor in astronomy at UMD.
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Additional participants in the consortium include Pomona College; San Diego State University; Los Alamos National Laboratory; University of Wisconsin-Milwaukee; Tokyo Institute of Technology; National Central University in Taiwan; Indian Institute of Astrophysics in Bengalore, India; Inter-University Centre for Astronomy and Astrophysics in Pune, India; Weizmann Institute of Science in Israel; Stockholm University in Sweden; and Humboldt University in Germany.