2020ApJ...898..160E -
Astrophys. J., 898, 160-160 (2020/August-1)
Low-albedo surfaces of lava worlds.
ESSACK Z., SEAGER S. and PAJUSALU M.
Abstract (from CDS):
Hot super-Earths are exoplanets with short orbital periods (<10 days), heated by their host stars to temperatures high enough for their rocky surfaces to become molten. A few hot super-Earths exhibit high geometric albedos (>0.4) in the Kepler band (420-900 nm). We are motivated to determine whether reflection from molten lava and quenched glasses (a product of rapidly cooled lava) on the surfaces of hot super-Earths contribute to the observationally inferred high geometric albedos. We experimentally measure reflection from rough- and smooth-textured quenched glasses of both basalt and feldspar melts. For lava reflectance values, we use specular reflectance values of molten silicates from non-crystalline solids literature. Integrating the empirical glass reflectance function and non-crystalline solids reflectance values over the dayside surface of the exoplanet at secondary eclipse yields an upper limit for the albedo of a lava-quenched glass planet surface of ∼0.1. We conclude that lava planets with solid (quenched glass) or liquid (lava) surfaces have low albedos. The high albedos of some hot super-Earths are most likely explained by atmospheres with reflective clouds (or, for a narrow range of parameter space, possibly Ca/Al oxide melt surfaces). Lava planet candidates in TESS data can be identified for follow-up observations and future characterization.
Abstract Copyright:
© 2020. The American Astronomical Society. All rights reserved.
Journal keyword(s):
Exoplanet surface characteristics - Experimental techniques - Super Earths - Exoplanet atmospheres - Exoplanet surface composition - Interdisciplinary astronomy
Simbad objects:
9
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