Metal clouds turn scorching hot exoplanet into the universe's largest mirror

[Judi Lynn]

By Robert Lea published about 9 hours ago
"It's a planet that shouldn't exist."



An illustration of the exoplanet LTT9779b as it orbits its star (Image credit: Ricardo Ramírez Reyes (Universidad de Chile))


Astronomers have discovered the most reflective planet outside the solar system ever seen. The ultra-hot extrasolar planet, or exoplanet, acts like a cosmic mirror because it is covered by reflective clouds of metal.

The planet, designated LTT9779 b, is located around 264 light-years from Earth and reflects around 80% of the light that shines on it from its parent star. As a comparison to LTT9779 b, Earth reflects just 30% of the light that falls on it from the sun. The ultra-hot LTT9779 b is so reflective that it is the first exoplanet found that gives the solar system's shiniest planet, Venus, a run for its money; Venus has a thick layer of clouds that reflect around 75% of incident sunlight.

While LTT9779 b was first discovered by NASA's Transiting Exoplanet Survey Satellite (TESS) mission in 2020, the world's highly reflective nature wasn't uncovered untn

The exoplanet is, in turn, almost five times as wide as Earth, meaning it is also the largest cosmic mirror ever discovered. "Imagine a burning world, close to its star, with heavy clouds of metals floating aloft, raining down titanium droplets," research co-author and Diego Portales University astronomer James Jenkins said in a statement.

More:
https://www.space.com/exoplanet-largest-mirror-metal-clouds?utm_source=notification

[JoeOtterbein]

1. K n R ! Thanks for posting!...

...Another WOW moment for me!

[eppur_se_muova]

2. Clouds of metallic COMPOUNDS, such as mixed oxides of Ti and other metals.

Astronomers use "metal" in an odd sense -- only implying the presence of metallic elements, but not necessarily in their elemental, i.e. metallic, form, which is how others use the term.

Most of the compounds used in the model described in the original pub'n would be rocks at normal temps.

The temperature of LTT 9779 b is high. In order to study the extreme cases, we decided to consider titanium-based condensates, which are the most refractory condensates that can form in hot exoplanets together with silicate clouds, which have often been considered in previous studies of hot Jupiters (Lecavelier des Etangs et al. 2003; Parmentier et al. 2016; Wakeford et al. 2017). Whereas silicate clouds have been used in previous studies with the ScCHIMERA code (Mai & Line 2019), we had to specifically include titanium-based condensates inside the code. Because the equilibrium condensation chemistry of titanium is complex, we decided to consider all the species as a single “titanium cloud” that are predicted to condense by the chemical equilibrium applications (CEA) code: Ti4O7, MgTi2O5, Ti3O5, Ti4O7, CaTiO3, Ti4O7, Ca4Ti3O10, Ca3Ti2O7, andTi2 O3. We then considered this titanium cloud to have the same optical properties as CaTiO3 clouds.

https://www.aanda.org/articles/aa/full_html/2023/07/aa46117-23/aa46117-23.html

The Ti=O bond is one of the strongest in the Universe; IR bands due to TiO show up in stars at higher temps than any other molecular absorption band.

TiO2 is familiar as "titanium white" pigment in paints, and yes it is *highly* reflective as a solid, but absorbs IR in the vapor phase.