A planet surrounded by reflective metallic clouds is the most luminous exoplanet known to date. The ultra-hot celestial body reflects no less than 80 percent of the light that falls on it from its star, the European space agency ESA announced on Monday.
In comparison, Venus with its thick layer of clouds reflects about 75 percent of the sunlight, while Earth only reflects about 30 percent. The exoplanet LTT9779b studied with the European space telescope CHEOPS is about the size of Neptune and “the largest ‘mirror’ in the Universe known today”.
Clouds of silicate mixed with metals
A year on LTT9779b, ie one orbit around its star, takes only 19 hours, the astronomers report. The reflective clouds are usually composed of silicate — the substance that makes up sand and glass — mixed with metals such as titanium.
According to the research team led by Sergio Hoyer of the Marseille Astrophysics Laboratory, the star-facing side of the planet is about 2,000 degrees Celsius — any temperature above 100 degrees is too hot for water clouds to form.
“A Planet That Shouldn’t Exist”
The brilliance isn’t the only surprising thing about the LTT9779b, they said. Its size and temperature make it what is known as an ultra-hot Neptune – never before has one been found so close to its star. “It’s a planet that shouldn’t exist,” says co-author Vivien Parmentier of the Observatory of the Côte d’Azur. Experts assumed that with planets closing, the entire atmosphere was usually blown away, leaving only bare rocks.
Metallic clouds prevent the planet from evaporating
Hoyer explained that it was probably the metallic clouds that prevented the planet from evaporating. In addition, the high metal content of the atmosphere makes it difficult to blow away. The team’s results are published in the journal Astronomy & Astrophysics.
According to ESA, most planets reflect only a small fraction of the light coming from their star. Either because they have an atmosphere that absorbs a lot of light, or because they have a dark or rough surface. Exceptions are frozen ice worlds or planets like Venus with a reflective cloud layer.
CHEOPS (standing for Characterizing Exoplanet Satellite) is a joint ESA-Swiss mission led by the University of Bern in collaboration with the University of Geneva. The observatory in space observes exoplanets, i.e. planets orbiting other stars.
Source: Krone
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