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Proposal ID = 12507
Principle Investigator =  Adam Kraus  - University of Hawaii
Title = "The Formation and Fundamental Properties of Wide 
      Planetary-Mass Companions"
Time = Feb 27, 2012 17:00:52 - 18:48:49
Target =  PDS70
Instrument = WFC3/UVIS

Background:

Most known extrasolar planets are quite close to their central star, primarily due to selection effects imposed by the method used to detect them. For example, a relatively high mass planet in a small radius orbit will cause large radial velocity variations, which makes them easy to detect. Similarly, these same types of planets are more likely to cause transits across the stars surface, resulting in small photometric variations which provide another method to detect extrasolar planets. However, there is also a class of objects at the other extreme, with very large orbits (50 - 500 Astronomical Units [AU], where the radius of Neptune's orbit is 30 AU). These objects can have large separations on the sky from their central star, making it possible to detect them against the glare of the star. In many cases these "Wide Planetary-Mass Companions" are found in the dusty accretion disks around a young star. This study is designed to provide basic information about these companions, with the hope of better understanding the accretion processes responsible for the formation of planets.

Paraphrasing from the abstract:

Over the past five years, direct imaging surveys for extrasolar planets have discovered a small but significant number of planetary-mass companions at separations >50 AU from their host stars. These wide companions pose a significant challenge to models of planet formation and of substellar atmospheres and evolution, and there are still many puzzling questions regarding their formation and fundamental properties. To address these open topics, we propose a WFC3 optical imaging survey for 25 orbits to study 12 planetary-mass companions. Our survey has three goals: 1) to use UBV and narrowband Halpha photometry to determine if (and how much) of these companions are accreting out of circumplanetary disks, 2) to use broadband optical photometry to measure their temperatures and luminosities by estimating their optical spectral types, and 3) to exploit the stable HST PSF to test whether any of the companions are marginally resolved binary pairs. None of these goals can be pursued from the ground, where high-resolution observing techniques are limited to near-infrared wavelengths and yield less stable PSFs.


You can find most of this information and more from the following webpage: http://www.stsci.edu/hst/ by entering "12507" in the Prop. ID box.


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