Astronomers identify molecules in space by matching observed radio signals with measurements made on Earth. By this method, nearly 200 simple molecules (such as water and ammonia) have been identified in our Milky Way galaxy. In this research, scientists will make careful laboratory measurements of new molecules that could be detected by radio telescopes. They will make very precise measurements of the molecules' signature, then go to telescopes to search for these signals in space. The scientists will search for these molecules by observing clouds of gas surrounding stars which blow carbon, oxygen and other elements off their outer layers. Molecules form as the gas from stars cool, and some of these molecules subsequently accumulate and form clumps called 'dust'. These scientists will learn what types of molecules are formed in space around these stars. They are particularly interested in molecules familiar on Earth but which are unknown in space, like silicon oxides (e.g. sand), aluminum oxide (the white film on unpainted aluminum) and titanium oxide (the white color in paint and active component in sunscreen). Some of these oxides of silicon, aluminum, and titanium are thought to be the building blocks of the dust that ultimately forms planets outside our own Solar System.
This research begins with laboratory measurements of rotational spectra of new complex molecules containing either two or three silicon, aluminum, or titanium atoms. These molecules are more complex than those previously measured. Next radio astronomers will unravel the chemistry in the inner envelopes of late-type carbon- and oxygen-rich evolved stars, which are a major source of planet forming dust.
Owing to many uncertainties in the chemical models of these sources, it is only through an empirical approach, which entails an integrated program of laboratory measurements and astronomical observations at high angular resolution and sensitivity, that astronomers may understand these complex regions. The molecules will be produced in widely used laboratory sources (either glow discharge, discharge nozzle, or laser ablation); their rotational spectra will be measured in the centimeter, millimeter, and sub-millimeter bands either with a Fabry-Perot cavity, broadband chirped pulse spectrometer, or non-resonant absorption cell; and the spectra will be analyzed with standard Hamiltonians and computer programs.
The search for the new molecular species in the laboratory will be guided by high level quantum chemical calculations of the structures which will be done by our expert collaborators, and will draw on 30 years of work on reactive molecules of astrophysical interest by our group. In addition to the contribution of this work to astronomy, direct detection of elusive titanium oxides, aluminum oxides, and silicon-bearing molecules in the laboratory will provide detailed information about their structures, which in turn will help applied physicists address vexing questions about the elementary reactions that govern the growth and their wide range of photo-catalytic and photovoltaic applications.
This research combines chemistry, electronics, physics and astronomy and is as an excellent topic for teaching, training, and learning. The outreach plan is two-pronged: (1) Provide mentorship and research opportunities to undergraduate and graduate students through programs at the Smithsonian Astrophysical Observatory (SAO) and Harvard; and (2) Create a spectral line molecular radio astronomy module for an innovative learning tool, called 'Spectral Explorer'.
The Spectral Explorer is a browser-based spectra visualization and analysis tool. The Spectral Explorer will be used in both high school classroom and public outreach learning settings. The SAO Science Education Department (SED) is developing these events. As part of this effort, the SAO spectroscopy laboratory will be actively engaged in the planning and execution of specific tutorials, videos, spectral datasets, and case study resources which will be centered on the research described in this proposal. The Spectral Explorer lab will be disseminated via partnerships with the NSF, NASA and Smithsonian Affiliations networks to the ten thousand educators currently using SED resources and to the more than 50,000 public/citizen science users.
