Report - School of Physics
Report - School of Physics
Report - School of Physics
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
4.6 Open Areas: Survey Mission Beyond Kepler/Eddington<br />
The absence <strong>of</strong> specific survey missions beyond 2015 noted in Section 4.1 can only be<br />
justified once all interesting targets in the sky to be studied in the future have been<br />
discovered. For small terrestrial planets, the Kepler mission is the only approved<br />
discovery mission. Even with Eddington, statistics <strong>of</strong> the occurrence <strong>of</strong> Earth-mass<br />
planets will still be poorly known, and the need for a larger, more performant, space<br />
transit survey seems already rather compelling. A case could also be made for an<br />
all-sky transit survey from space, in order to find the nearest transiting terrestrial<br />
planets, facilitating follow-up with astrometry and spectroscopy. The arguments<br />
presented in Section 3.3, ‘Understanding the Planetary Population <strong>of</strong> our Galaxy’,<br />
also draw attention to a lack <strong>of</strong> further search programmes for terrestrial planets<br />
beyond Kepler.<br />
4.7 Other Considerations<br />
4.7.1 Fundamental Physical Data<br />
It is not evident that present knowledge <strong>of</strong> basic atomic data is adequate to understand<br />
the high-resolution spectra <strong>of</strong> normal host stars over the broad wavelength<br />
region discussed in Section 4.4.1, and the spectral signatures <strong>of</strong> planets and their<br />
atmospheres. Preliminary investigations suggest that there is a need for improved<br />
atomic and molecular lines particularly in the near infrared. To illustrate the point<br />
and the potential risk <strong>of</strong> inadequate atomic data we give two examples: (i) Li in low<br />
mass post-AGB stars; expanded wavelength tables for Ce have shown that the line at<br />
670.8 nm previously identified with (slightly redshifted) Li is coincident with a Ce II<br />
line at 670.8099 nm. Abundance analysis subsequently showed that for all practical<br />
purposes no Li is present in these stellar photospheres (Reyniers et al., 2002). This<br />
is an important finding for stellar evolution and nucleosynthesis since an elaborate<br />
mechanism had to be evoked in order to explain the presence <strong>of</strong> Li in these evolved<br />
stars; (ii) variability <strong>of</strong> the fine structure constant: evidence from the absorption<br />
features in distant quasars suggested a variability <strong>of</strong> the fine structure constant over<br />
time. Originally, these studies had been hampered by limited accuracy <strong>of</strong> laboratory<br />
wavelengths for the relevant species (Pickering et al., 2000). Most recently a further<br />
complication introduced by the sensitivity to the abundance <strong>of</strong> heavy isotopes has<br />
been described for Mg (Ashenfelter et al., 2004), where uncertainties in the isotope<br />
ratios might imitate a variation <strong>of</strong> the fine structure constant at the observed level.<br />
Nearer to the issues <strong>of</strong> exo-planets, the debate about the nature <strong>of</strong> Jupiter’s interior<br />
centres on the (unknown) equation <strong>of</strong> state <strong>of</strong> H/He mixtures at high pressures.<br />
Regardless <strong>of</strong> the exact details these examples illustrate that the lack <strong>of</strong> accurate<br />
and reliable atomic data can lead to serious misinterpretation <strong>of</strong> astrophysical data.<br />
When dealing with fundamental issues such as the properties <strong>of</strong> extra-solar planets<br />
68