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Stars and the Galaxy

Pan-STARRS will catalog 99% of the stars in the northern hemisphere that have ever been observed by visible light -- many billions of them. These individual stars will not be confined to the Milky Way galaxy; stars in nearby galaxies will routinely have their colors and positions noted, and will be checked regularly for variablity. The stellar database that results from Pan-STARRS will be a goldmine for statistical studies of how different kinds of stars are distributed in their parent galaxies. Selected regions of the sky, such as young star clusters, will be searched in even greater depth. The ensemble of positional information of stars observed with Pan-STARRS, whether nearby or distant, will lead to what will become the de-facto astrometric reference catalog for faint objects.

Most stars detected by Pan-STARRS will never merit individual attention beyond an entry in a computer database, but a minority of them will stand out from the crowd by moving or varying. It is mainly these stars that will catch astronomers interest. Among the variable stars that Pan-STARRS will detect are eclipsing binaries, erupting stars, microlensing events, and regular variables such as Cepheids and RR Lyrae stars. These latter are particularly useful in that they can be used for distance measurements out to 10 Mpc, encompassing nearby galaxies as well as the halo and most distant regions of our own Galaxy.

Exoplanet Searches

Pan-STARRS offers an excellent opportunity for detecting planets around distant stars. When an extrasolar planet transits in front its parent star, the slight dimming of that starlight may be detectable, even if the planet is too faint to be seen. By measuring the brightness of thousands of individual stars in a large star cluster like NGC 6791 every few weeks we can expect to see about 100 transits suitable for follow-up studies. Pan-STARRS is also sensitive enough to detect the passage of an Earth-size planet in front of a Brown Dwarf.

Solar Neighborhood

We know plenty about the large, luminous stars near the Sun, but we know much less about the much more numerous cool, low luminosity stars, since they are hard to pick out from the background of more distant objects. Most stars that are within about 100 parsecs from the Sun, however, have detectable parallaxes and/or proper motions that mark them out as our neighbors. Since Pan-STARRS will survey the whole sky to 24th magnitude every few days, it can generate an unprecedented three-dimensional catalog of our immediate stellar neighbors. This catalog will be a particularly rich resource for the study of low-mass stars, brown dwarfs, and white dwarfs.

Evolution and Death of Stars

When stars die they usually become white dwarfs or neutron stars. These compact objects tend to be difficult to observe directly, but they readily draw attention to themselves when they are part of a close binary pair with a brighter, larger companion star. Pan-STARRS will be set up to search for the flares and other transient brightness fluctuations that arise as matter is drawn off the larger star towards the compact object. Among the interacting binary systems we expect to discover will be precursor type Ia supernovae, microquasars, millisecond pulsars, and cataclysmic variables. The discovery and study of such systems provide the only laboratories through which the extreme physical environments of high gravity, high temperature, accretion and high magnetic field can be studied in detail.

Young Stellar Objects

The youthful exuberance of young stars makes them among the most variable of all astronomical phenomena, and essentially all known young stars show photometric variability at some level. Brightness and color changes arise from rotation, instinsic luminosity variations, orbiting dust clouds, accretion processes, eruptions, and magnetic and binary effects. THe ability of Pan-STARRS to search the whole of the galactic plane for variable sources will provide a vast resource for the study of star formation.

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