High-resolution observations reveal reflected light from ultra-hot exo-Neptune LTT 9779 b

Star system: LTT 9779 | Distance from the Sun: 264 light years

The ultra-hot Neptune-mass planet LTT 9779 b has been studied through the detection of its reflected starlight. Because planets are much fainter than their host stars, capturing the light they reflect is a significant technical challenge. By observing the system at high spectral resolution, investigators were able to isolate the faint signal of light bouncing off the planet, providing new information about its atmosphere.

The findings were gathered using the ESPRESSO spectrograph, an instrument designed to capture precise light data from stars and planets. By combining data from multiple observation periods and using mathematical models to filter the signal, the presence of the planet's reflected light was confirmed.

This signal indicates that the planet has a geometric albedo of 0.88, meaning it is highly reflective. This brightness suggests the presence of high-altitude clouds or specific scattering processes in the atmosphere that bounce light back into space. The reflection was notably stronger at shorter, bluer wavelengths of light.

While this study identifies the planet's high reflectivity, it does not provide a full chemical breakdown of the atmosphere. The results demonstrate the capability of ground-based high-resolution instruments to study the reflected light of distant planets, setting a foundation for future studies of smaller or cooler worlds.

Key findings
- Detection of reflected light from LTT 9779 b with a signal-to-noise ratio of 5.4.
- Measured a planet-to-star flux ratio of 102 parts per million.
- Calculated a geometric albedo of 0.88, indicating a highly reflective atmosphere.
- Confirmed reflectivity increases toward blue wavelengths of light.
- Results suggest the presence of high-altitude clouds or scattering particles.

Scientific study

High-resolution detection of reflected light from the exo-Neptune LTT-9779 b (external link)