Title of programme: Constraining the Scattering Properties of Condensates in the Ultrahot Neptune, LTT 9779b
Abstract: By studying the thermal emission and reflected light from transiting exoplanets when they pass behind their host stars, we can study in detail their atmospheric properties. The emission in the infrared allows us to determine the radiant heat from the planet, providing a dayside temperature for example, whereas in the optical the detected energy generally comes from the host star’s scattered light, allowing a calculation of the planet’s albedo. The recent discovery of the first Ultrahot Neptune, LTT 9779b, provides a benchmark planet to study Neptune-like atmospheres in extreme environments. We already have Spitzer infrared secondary eclipses from the planet, providing a dayside temperature of 2100 K, and a likely detection of CO. The TESS lightcurve that originally detected the primary transits, also allowed a marginal detection of the optical secondary eclipse. The measured value of 60 ppm, is more than two times higher than the maximum planetary emission at these wavelengths, suggesting strong scattering is at play due to high altitude aerosols. We therefore aim to detect the optical secondary eclipse using CHEOPS, with a precision of ~20 ppm, confirming the tentative results from TESS. The bluer CHEOPS passband will anchor our global circulation models, allowing us to constrain the reflected light component and characterize the layer of absorbers in the atmosphere. This work will be a first for such a world, representing a genuine landmark in the field.
Temporal Coverage
2020-09-27T22:45:00Z / 2020-09-28T03:42:00Z
Version
3.0
Mission Description
CHEOPS (Benz et al., https://doi.org/10.1007/s10686-020-09679-4) is a European Space Agency (ESA) mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the United Kingdom.
The satellite has a single payload comprising an ultra-high precision photometer covering the 330 - 1100 nm wavelength range in a single photometric band. Observations are made as part of the Guaranteed Time Observing Programme that is formulated by the CHEOPS Science Team, and the Guest Observers Programme through which the Community at large can apply for CHEOPS time.
