The not so Quiet Night Sky
Traditionally humans have looked up to the sky as a majestic, unchanging place, much more dignified than our imperfect, ever changing world. However, the sky is not always so quiet. Even with our naked eye, we can sometimes see changes, and early humans thought these might be bad omens. Chinese astronomers were among the first to record "new stars" appearing in the sky. Nowadays we know that these new stars often signify very violent events in the universe, such as explosions of massive stars, when exotic objects are formed such as black holes and neutron stars. Also, in other wavelgnths of radiation, such as X rays and radio waves, the sky is much less quiet than in visible light. We can often learn very extreme physics from these events, because the conditions in them are very different from what we can observe in laboratories on Earth. In this talk, I will show some of the things we have learnt from observing these so-called transient sources, and some of the questions we are still trying to answer. About the speaker: Prof. Ralph Wijers has been professor of high-energy astrophysics at the University of Amsterdam since 2002. He specialises in energetic explosions from extreme objects such as black holes and neutron stars and is PI of the AARTFAAC all-sky radio telescope. He got his MSc from Leiden Observatory and his PhD from the University of Amsterdam. He went on to Princeton on a NASA Compton Fellowship and Cambridge on a Royal Society Fellowship, after which he became assistant professor at Stonybrook University. He is a VICI and ERC Advanced Investigator laureate and winner of the 2002 EU Descartes Prize for his discoveries in gamma-ray bursts, with an international team. He teaches enthusiastically from the broad undergraduate level to highly specialised graduate courses, and is actively involved in outreach. Astrid and he have two daughters, who study astrophysics and mathematics, and medicine. He is a member of several national and international scientific governing and advisory councils. Since 2011, he is director of the Anton Pannekoek Institute for Astronomy.
Prof. Ralph A.M.J. Wijers University of Amsterdam
Auditorium of Tsinghua University
Tsinghua Center for Astrophysics
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