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The Active Universe

Since Pan-STARRS surveys the whole sky every few days, it offers an unprecedented opportunity to discover and monitor those rare, explosive objects that challenge the limits of our understanding of astrophysics. Some of these events will be discovered as a result of Pan-STARRS routine monitoring of the whole sky, while fainter ones will be searched for with directed deeper surveys.

Supernova Science

Type Ia supernovae are astronomy's most luminous "standard candle." By monitoring the apparent brightness of these rare events we can estimate the distance to a galaxy independent of its redshift, and hence determine if and how Hubble's law has changed over the history of the Universe. It was measurements of Type Ia supernova distances that provided the first clues that rate of expansion of the Universe may be accelerating, and the first hint of the existence of "dark energy." Supernova distances are still one of the very few ways of studying this mysterious pressure, which appears to be the dominant form of energy in the Universe.

Pan-STARRS will find many candidate Type Ia supernovae in the course of its regular sky monitoring; but these discoveries will need to be followed up on other telescopes. By monitoring a few patches of sky every four days for a year, however, we can expect to discover and obtain light curves for about 5000 Type Ia supernovae, without using any other instrument.

Gamma-Ray Bursts

Gamma ray bursts are the most powerful known events in the Universe, and are believed to arise from the gravitational collapse of massive stars . The bursts themselves are detected by satellites, but the afterglow from a burst can be watched visually for about a day after the event.

The hundreds of afterglows that Pan-STARRS will detect will provide a statistical basis for determining the astrophysical environments that foster their birth.

Active Galactic Nuclei

Active galactic nuclei (AGNs), such as quasars, are our main beacons from the early Universe. These objects are so luminous that they can be detected at distances corresponding to z = 7. At this redshift we are looking back nearly to the age of recombination, the time at which ultraviolet light from the first generation of stars became strong enough to ionize the hydrogen in the Universe and make it transparent.

Pan-STARRS will detect AGNs by both color and variablity. The most distant ones will require a dedicated deep survey to magnitude 29.

Next: Galaxies and Cosmology

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