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2007 Annual Science Report

University of Arizona Reporting  |  JUL 2006 – JUN 2007

Executive Summary

During the year further activities have come to fruition.

Module 1: The Building Blocks of Life

There has been progress in understanding the development of organic molecules in space as arising initially from the materials ejected by red giant stars. First the re has been a continuation of the study of transport of materials through the planetary nebula phase. In addition to the CCH reported last year, we have now added C3H2. Together the se give a clear demonstration of the persistence of C-C bonded molecules into the interstellar medium despite the intense UV radiation field of the planetary nebula phase. The observed molecules, in so far as we have sought the m seem to match with those reported to be observed in absorption in the line of sight to quasars. The significance of the se observations is that complex molecule formation in the interstellar medium and in dense molecular clouds does not have to start from scratch, but the re are a core suite of molecules that can act as catalysts and substrates towards the formation of more complex molecules.

There has been a major effort to study the ejected molecules by the red supergiant star VY Canis Majoris. One paper has been published in Nature, and two others have been submitted to the Astrophysical journal. Molecules observed , included the silicon element of Earth and all the key elements of life, carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur. As a result of this and additional studies, including o the r stars, a paper has been submitted discussing observations of four phosphorus bearing molecules observed being ejected into the interstellar medium.

Stars are part of a grand cosmic cycle wherein matter is created, transformed, and recycled. Material is created within a star and eventually ejected outward as the star grows old and ultimately dies. That matter can become the stuff of new solar systems, and may even end up in life forms. This work fur the rs our understanding of how the chemistry of stars may be woven into the thread of life in the universe.

VY CMa’s outer shell is oxygen-rich, making it part of a group of stars that have been poorly studied even though the majority of interstellar matter is thought to originate from the m. The study revealed a variety of unexpected chemical compounds in the star, including NaCl (table salt), PN, PO , HNC, and HCO + , demonstrating a remarkable chemical diversity relative to its carbon-rich counterparts.

Module 2: Formation of a Habitable World

Module 2 work has been directed towards exploring the relationship between pre-planetary disks, debris disks, and the presence of observable planets. In addition this module has explored indications of the evolution of planetary systems after formation.

Many stars have been observed in the Spitzer Telescope FEPS (Formation and Evolution of Planetary Systems) survey for solid particle emission. The statistics of mid-IR emission suggest that many or perhaps most sun-like stars form terrestrial planets. Those stars independently found to have gas giant planets by radial velocity studies do not seem to significantly correlate with the presence of far infrared emission. Terrestrial planets and residual planetismals are likely more common than gas giant planets.

Observations of Spitzer Telescope targets seeking gas giant planets at large radii from the ir star, failed to find giant planets, indicating that at radii ~ 20 AU they have become rare or absent. While this is disappointing for the current searches, the prospects for the next generation of searches use 8m class telescopes and looking at smaller separations using new techniques under development with module 3 remains very promising.

A dynamical study to explore the possibility that the faint young sun paradox can be explained by early mass loss from the sun, found instead that it is unlikely. The rate of mass loss with time would be atypical of the rates and time change observed for solar type stars.

We have the first results in from our photometric survey of the variability of young solar type stars. We expect that by next year the re will be adequate data for a preliminary analysis.

There has been an attempt to determine what physical process causes astronomical amorphous silicates to crystallize in some planetary systems. Results have been puzzling. No correlation has been found with age, stellar mass, or presence of a binary companion.

Module 2 members have been involved in two activities as part of the Director’s Strategic Activities using discretionary funds. Meyer is leading an activity on “Chemical Constraints on the Formation of Habitable Worlds”. Members are also supporting a study by Steinn Sigurdsson (PSU) on “Extreme Habitability".

Module 3: Nature of Planetary Systems

This module focuses on the direct detection and characterization of planetary systems.

This group is developing a variety of techniques to look at the region angularly close to the telescope diffraction core in order to search for planets. The techniques are different in different wavelength regions, because of the varying difficulty presented by atmospheric seeing, which is much more severe for the shorter wavelengths.

A near infrared survey at 1.6 microns is using simultaneous differential imaging (SDI) at the MMT and VLT, to seek images of young planets around nearby stars, by looking for evidence of the ir having a methane absorption band. A the rmal survey in the 3.8 and 4.8 micron bands micron regions is searching for evidence of cooler older planets by looking for the excess radiation the y show in the ir atmospheric opacity minimum near 4-5 microns. We are also developing detailed radiative transfer models of planetary atmospheres to predict flux levels for direct detection using ground based telescopes, and the space telescopes Spitzer, HST and JWST.

Two surveys have been completed this year. 45 stars have been surveyed with SDI, and 50 stars have been surveyed at 3.8 microns. There is also an ongoing survey for M dwarf stars for comparison with the ir higher mass companions. This first generation direct survey has shown that giant planet companions are rare at distances ~ 20 AU from the ir star. This is surprising, because this is near the peak of the binary star distribution. The emphasis has now shifted to the much more difficult task of looking for closer planets.

A new approach is now being made with the apodizing plate invented here (see last year annual report). There is a focus on looking for planets at 0.4-1.0 arc second separation, corresponding to 4-10 AU for a star at 10pc. Deep observations of trial stars succeeded. A survey of the 25 brightest stars with this technique is now being initiated.

Alex Pavlov has been studying the early atmosphere of the Earth. It now seeacredbeen believed and the effects of this on climate are being considered. Pavlov has also been considering the effect of the Early Sun UV flux on atmospheric processes.

Module 1 and 2 members have been involved in activities as part of the Director’s Strategic Activities using discretionary funds. Woolf has led an activity to make observations of the Earth from cis-lunar space to make observations of Earth as a sample exoplanet. Earth is the only example we have of a habitable planet for which we can both obtain single pixel observations as e.g with TPF, and multi-pixel images and polarimetry to ground-truth the observations. There are special needs for spectropolarimetry, which by its phase variation my reveal the presence of liquid water by the polarized glint on the oceans, or the polarized scattering from clouds. There are also needs for phase coverage of Earth at all wavelengths. Such observations are not possible with Earthshine. A group of about 20 scientists has been developed to explore the possibility for a mission. First studies showed that such a mission could fit the cost cap of a SMEX satellite. Unfortunately the re appears to be inadequate current scientific support outside our group to move forward with such a mission at this time.

Module 4: Strengthening the Astrobiology Community

We have continued the two series of public lectures, the College of Science series, which was about global climate change, and the third year of our Templeton lectures on Astrobiology and the Sacred. We submitted a proposal to the Templeton Foundation for a fur the r year of lectures, and that proposal has been funded. For each of the se events we have also organized teacher-training workshops, run by Dr. T. Slater. Likewise the College of Science lecture series will be continuing this coming spring. In each of the se lecture series the LAPLACE team has been involved in the giving of lectures, the organization of the series, and in a display associated with the series at the University Science Library.

During the year, it became apparent that the University of Washington team of NAI was not going to be continued. Since we have had such successful interactions with this team we have continued our relationship by bringing Washington team members into our group. This includes Drs. Peter Ward , Don Brownlee, Roger Buick, John Baross, Woody Sullivan and Jody Deming. This has permitted NAI to fund an atmospheres experiment lab at U. Washington for Peter Ward , and a NASA postdoctoral fellow ( 1997) Dr. Julien Foriel has been able to work with Dr. Roger Buick.

Additional postdoctoral fellowships were obtained the previous year for Dr. Matt Pasek, working with Dr. Jonathan Lunine and Dr. Curtis Cooper working with Dr. Alex Pavlov.

Other activities that have fallen outside the three modules of our organization include studies related to the issue of the future of humanity. Dr. Roger Angel has explored both the possibilities of a solar sunshade for Earth to combat some of the effects of global warming, and has considered the pros and cons of having Earth satellites involved in ei the r the generation of solar electrical energy, or the transmission of energy at desert sites and its reflection to places where it would likely be used. However analyses have shown that it is more cost effective to generate solar energy on the ground, transmit it over high voltage aluminum power lines, and store it as gravitational potential energy in pumped water. There are also hopes for o the r storage systems. Angel is currently following up this work with non-NAI resources, to study reducing the cost of solar electricity production.